:-~
TUT 
007 
1955
*65014*
65014
DRAFT FINAL
FEASIBILITY STUDY
TUTU WELLS SITE
ST. THOMAS, U.S. VIRGIN ISLANDS
August 4,1995
Prepared by Geraghty & Miller, Inc.
BrenrerO'Dell, P.E.
Project Engineer
Thomas V. Danahy
Senior Scientist/Project Manager
Daniel A. Nachman
Vice President/Project Director
TUT 
OO7 
1956
GERAGHTY & MILLER, INC.
CONTENTS
Page
1. INTRODUCTION........................................................................................................ 1-1
1.1 PURPOSE OF THE FEASIBILITY STUDY................................................... 1-3
1.2 ORGANIZATION OF THE FEASIBILITY STUDY REPORT....................... 1-3
2. SUMMARY OF REMEDIAL INVESTIGATION RESULTS....................................... 2-1
2.1 SITE BACKGROUND....................................................................................2-1
2.1.1 Site Description, Geology, Hydrogeology, and Aquifer
Characteristics................................................................................2-1
2.1.1.1 Description.........................................................................2-1
2.1.1.2 Geology.............................................................................. 2-3
2.1.1.3 Hydrogeology.....................................................................2-5
2.1.1.4 Summary of Aquifer Hydraulic Characteristics ....................2-9
2.1.2 History of Known Public Concerns.................................................... 2-10
2.2 NATURE AND EXTENT OF CONTAMINATION........................................ 2-14
2.2.1 Soil Quality ....................................................................................... 2-14
2.2.1.1 Chlorinated VOCs in Soil....................................................2-17
2.2.1.2BTEXin Soil......................................................................2-18
2.2.2 Groundwater Quality......................................................................... 2-20
2.2.2.1 Chlorinated VOCs...............................................................2-20
2.2.2.2 Petroleum-Related Compounds...........................................2-22
2.2.2.3 Evaluation of the Potential Presence ofNonaqueous
Phase Liquids......................................................................2-23
2.3 CONTAMINANT FATE AND TRANSPORT ................................................ 2-26
2.4 BASELINE RISK ASSESSMENT..................................................................2-26
3. REMEDIAL ACTION GOALS AND GENERAL RESPONSE ACTIONS................... 3-1
GERAGHTY & MILLER, INC. 
TUT 
OO7 1958
CONTENTS (continued)
3.1 REMEDIAL ACTION OBJECTIVES AND PRELIMINARY
REMEDIAL GOALS................................................................................. 3-1
3.1.1 Remedial Action Objectives............................................................... 3-1
3.1.2 Preliminary Remedial Goals............................................................... 3-3
3.1.2.1 ARARs............................................................................... 3-3
3.1.2.2 To-Be-Considered Material................................................. 3-4
3.1.2.3 Remedial Action Levels and Cleanup Goals.................. ......3-4
3.2 IDENTIFICATION OF GENERAL RESPONSE ACTIONS........................... 3-5
4. IDENTIFICATION AND SCREENING OF REMEDIAL TECHNOLOGIES.............. 4-1
4.1 TECHNOLOGY IDENTIFICATION.............................................................. 4-1
4.2 TECHNOLOGY SCREENING CRITERIA..................................................... 4-2
4.3 IDENTIFICATION AND SCREENING OF REMEDIAL
TECHNOLOGIES FOR SOIL...................................................................4-3
4.3.1 No Action.........................................................................:................4-3
4.3.2 Institutional Controls.........................................................................4-4
4.3.3 Containment......................................................................................4-5
4.3.4 Treatment..........................................................................................4-6
4.3.4.1 In-Situ Soil Vapor Extraction..............................................4-7
4.3.4.2 In-Situ Bioventing...............................................................4-9
4.3.5 Removal Technologies.......................................................................4-10
4.3.5.1 Biopiles/Ex-Situ SVE..........................................................4-11
4.3.5.2 On-Site Thermal Desorption................................................4-12
4.3.5.3 Incineration.........................................................................4-13
4.4 IDENTIFICATION AND SCREENING OF REMEDIAL
TECHNOLOGIES FOR GROUND WATER.............................................. 4-14
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GERAGHTY & MILLER, INC.
TUT 
007 
1959
Ill
CONTENTS (continued)
Page
4.4.1 No Action..........................................................................................4-14
4.4.2 Institutional Controls.........................................................................4-15
4.4.2.1 Access Restrictions............................................................. 4-15
4.4.2.2 Alternate Water Supply....................................................... 4-16
4.4.2.2.1 Public Water Supply Extension............................. 4-16
4.4.2.2.2 Trucking Water.................................................... 4-17
4.4.2.2.3 New Community Well........................................... 4-17
4.4.3 Collection/Containment.....................................................................4-18
4.4.3.1 Extraction...........................................................................4-18
4.4.3.1.1 Extraction Wells...................................................4-18
4.4.3.1.2 Extraction/Injection Wells..................................... 4-19
4.4.3.2 Subsurface Drains...............................................................4-20
4.4.3.3 Well Points..........................................................................4-21
4.4.3.4 Vertical Barriers..................................................................4-22
4.4.3.4.1 Slurry Wall........................................................... 4-22
4.4.3.4.2 Synthetic Membrane CutoffWalls......................... 4-23
4.4.3.5 Enhanced Groundwater Recovery .......................................4-24
4.4.3.5.1 Bedrock Fracturing...............................................4-24
4.4.3.5.2 Vacuum Enhanced Recovery................................4-25
4.4.4 Treatment..........................................................................................4-26
4.4.4.1 In-Situ Treatment................................................................4-26
4.4.4.1.1 Air Sparging.........................................................4-26
4.4.4.1.2 Bio-Sparging........................................................4-27
4.4.4.2 Ex-Situ Treatment...............................................................4-27
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GERAGHTY^ MILLER, INC 
"JT 
°07 
196°
IV
CONTENTS (continued)
4.4.4.2.1 Air Stripping......................................................... 4-28
4.4.4.2.2 Granular Activated Carbon Adsorption................. 4-29
4.4.4.2.3 Filtration...............................................................4-30
4.4.4.2.4 Precipitation, Flocculation, and Sedimentation...... 4-31
4.4.4.2.5 Reverse Osmosis...................................................4-31
4.4.4.2.6 Ion Exchange........................................................ 4-32
4.4.4.2.7 Ultraviolet Oxidation/Reduction ...........................4-33
4.4.4.2.8 GAC Fluidized Bed System .................................. 4-34
4.4.4.3 Natural Remediation ........................................................... 4-34
4.4.5 Discharge..........................................................................................4-35
4.4.5.1 Discharge to Publicly Owned Treatment Works................... 4-35
4.4.5.2 Discharge to a RCRA-Permitted Treatment, Storage,
and/or Disposal Facility....................................................... 4-36
4.4.5.3 Discharge to Surface Water.................................................4-37
4.4.5.4 Conveyance to Beneficial Non-Potable User........................ 4-38
4.4.5.5 Re-Injection........................................................................4-39
4.4.5.6 Distribution for Potable Use................................................4-40
4.5 TECHNOLOGIES RETAINED FOR FURTHER CONSIDERATION............ 4-41
4.6 FURTHER EVALUATION OF SCREENED TECHNOLOGIES.................... 4-44
4.6.1 Source Control Plans.........................................................................4-44
4.6.1.1 Texaco Tutu Service Station Source Control Plan...............4-45
4.6.1.2 Esso Tutu Service Station Source Control Plan...................4-45
4.6.2 Soil Remedial Technologies...............................................................4-46
4.6.2.1 Curriculum Center...............................................................4-48
4.6.2.2 Ramsay Motors...................................................................4-49
4.6.2.3 Texaco Tutu Service Station...............................................4-50
4.6.2.4 Tillett Gardens....................................................................4-50
4.6.2.5 Western Auto...................................................................... 4-51
4.6.2.6 Esso Tutu Service Station...................................................4-52
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GERAGHTY & MILLER, INC.
TUT 
007 
1961
CONTENTS (continued)
4.6.2.7 OHenry Dry Cleaners ......................................................... 4-52
4.6.3 Groundwater Remedial Alternatives................................................... 4-53
4.6.3.1 Collection and Containment ................................................4-54
4.6.3.2 Treatment...........................................................................4-58
4.6.3.3 Natural Remediation...........................................................4-62
5. DEVELOPMENT AND SCREENING OF REMEDIAL ALTERNATIVES................. 5-1
5.1 EVALUATION CRITERIA............................................................................. 5-1
5.2 DEVELOPMENT AND EVALUATION OF REMEDIAL
ALTERNATIVES FOR SOIL.................................................................... 5-2
5.2.1 SRA 1: No Action/Institutional Controls............................................5-5
5.2.1.1 Description of SRA1..........................................................5-5
5.2.1.2 Evaluation of SRA 1 ...........................................................5-6
5.2.2 SRA 2: Institutional Controls/Capping............................................... 5-7
5.2.2.1 Description of SRA 2.......................................................... 5-7
5.2.2.2 Evaluation of SRA 2........................................................... 5-8
5.2.3 SRA 3: Institutional Controls/Capping/In-Situ SVE (Soil and
Bedrock)/Excavation and Off-Site Disposal.................................... 5-10
5.2.3.1 Description of SRA 3..........................................................5-10
5.2.3.2 Evaluation of SRA 3 ........................................................... 5-13
5.2.4 SRA 4: Institutional Controls/Capping/Ex-Situ SVE/Excavation
and On-Site Disposal ......................................................................5-16
5.2.4.1 Description of SRA 4.......................................................... 5-17
5.2.4.2 Evaluation of SRA 4........................................................... 5-19
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GERAGHTY & MILLER, INC.
TUT 
OO7 
1962
VI
CONTENTS (continued)
5.2.5 SRA 5: Institutional Controls/Capping/In-Situ SVE
(Bedrock)/Excavation and............................................................... 5-22
5.2.5.1 Description of SRA 5..........................................................5-22
5.2.5.2 Evaluation of SRA 5 ........................................................... 5-23
5.3 DEVELOPMENT AND EVALUATION OF REMEDIAL
ALTERNATIVES FOR GROUNDWATER.............................................. 5-25
5.3.1 GRA 1: No Action/Institutional Controls........................................... 5-27
5.3.1.1 Description of GRA 1......................................................... 5-27
5.3.1.2 Evaluation of ORAL..........................................................5-28
5.3.2 GRA 2: Institutional Controls/Source Containment/POET
Systems/Treatment/Discharge.........................................................5-30
5.3.2.1 Description of GRA2.........................................................5-30
5.3.2.2 Evaluation of GRA 2........................................................... 5-32
5.3.3 GRA 3: Institutional Controls/Plume
Containment/Treatment/Discharge..................................................5-35
5.3.3.1 Description of GRA 3 .........................................................5-35
5.3.3.2 Evaluation of GRA 3...........................................................5-37
5.3.4 GRA 4: Institutional Controls/Source and Plume
Containment/Treatment/Discharge................................................. 5-39
5.3.4.1 Description of GRA4.........................................................5-39
5.3.4.2 Evaluation of GRA 4........................................................... 5-41
5.4 COMPARATIVE ANALYSIS OF ALTERNATIVES..................................... 5-44
5.4.1 Protection of Human Health and the Environment.............................. 5-44
5.4.2 Compliance with ARARs................................................................... 5-45
5.4.3 Short-Term Effectiveness .................................................................. 5-47
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GERAGHTY & MILLER, INC.
TUT 
O07 
1963
VII
CONTENTS (continued)
5.4.4 Long-Term Effectiveness................................................................... 5-48
5.4.5 Reduction in Toxicity, Mobility, and Volume..................................... 5-49
5.4.6 Implementability................................................................................ 5-49
5.4.7 Cost.................................................................................................. 5-50
5.4.8 Summary of Comparative Analysis of Alternatives............................. 5-51
6. PRE-DESIGN ACTIVITIES.....;................................................................................... 6-1
6.1 PRE-DESIGN ACTIVITIES FOR SOIL REMEDIATION.............................. 6-1
6.2 PRE-DESIGN ACTIVITIES FOR GROUNDWATER REMEDIATION........ 6-2
6.3 PRE-DESIGN ACTIVITIES FOR TREATMENT SYSTEMS ........................6-3
7. REFERENCES ............................................................................................................. 7-1
TABLES
2-1. 
Summary of Soil Screening Levels Provided by the U.S. Environmental Protection
Agency, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
2-2. 
Summary of Carcinogenic Risks Exceeding the U.S. Environmental Protection Agency
Guidance Value, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
2-3. 
Summary of Noncarcinogenic Risks Exceeding the U. S. Environmental Protection Agency
Hazard Quotient of 1, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
2-4. 
Summary of Analytes Detected in Soil Above Soil Screening Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
3-1. 
Groundwater Chemical-Specific Remedial Action Levels Identified for the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
3-2. 
Summary of Potential Federal Location-Specific Applicable or Relevant and Appropriate
Requirements, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
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GERAGHTY & MILLER, INC.
TUT 
O07 1964
VUl
TABLES (continued)
3-3. 
Summary of Potential Federal Action-Specific Applicable or Relevant and Appropriate
Requirements, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
3-4. 
Summary of Potential Federal Chemical-Specific Applicable or Relevant and Appropriate
Requirements and To-Be-Considered Material, Tutu Wells Site, St. Thomas, U.S. Virgin
Islands.
3-5. 
Summary of Potential U.S. Virgin Islands Location-Specific Applicable or Relevant and
Appropriate Requirements, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
3-6. 
Summary of Potential U.S. Virgin Islands Action-Specific Applicable or Relevant and
Appropriate Requirements, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
3-7. 
Summary of Potential U.S. Virgin Islands Chemical-Specific Applicable or Relevant and
Appropriate Requirements, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
3-8. 
Summary of Analytes Detected in Groundwater Above Remedial Action Levels at the
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
4-1. 
Development and Screening of Technologies for Soil, Tutu Wells Site, St. Thomas, U.S.
Virgin Islands.
4-2. 
Off-Gas Treatment Technology Evaluation, Tutu Wells Site, St. Thomas, U.S. Virgin
Islands.
4-3. 
Development and Screening of Technologies for Groundwater, Tutu Wells Site, St.
Thomas, U.S. Virgin Islands.
4-4. 
Summary of Influent Concentrations and Maximum Contaminant Levels, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
4-5. 
Summary of Estimated Impacted Soil Volumes, Tutu Wells Site, St. Thomas, U.S. Virgin
Islands.
4-6. 
Evaluation of No Action/Institutional Controls Technologies Option on Property-Specific
Basis, Tutu Wells Site, U.S. Virgin Islands.
4-7. 
Evaluation of Capping Technology Option on Property-Specific Basis, Tutu Wells Site, St.
Thomas, U.S. Virgin Islands.
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GERAGHTY 6? MILLER, INC. 
TUT 
°°7 
1965
IX
TABLES (continued)
4-8. 
Evaluation of In-Situ SVE and Bioventing Technologies Option on Property-Specific
Basis, Tutu Wells Site, U.S. Virgin Islands.
4-9. 
Evaluation of Ex-Situ SVE and Biopiles Technologies Option on Property-Specific Basis,
Tutu Wells Site, U.S. Virgin Islands.
4-10. Evaluation of Excavation and Off-Site Disposal Technology Option on Property-Specific
Basis, Tutu Wells Site, U.S. Virgin Islands.
4-11. Summary of Proposed Pumping Rates for New Recovery Wells, Tutu Wells Site, U.S.
Virgin Islands.
4-12. 
Summary of Potential POET Supply Well Installations for GRA 2, Tutu Wells Site, St.
Thomas, U.S. Virgin Islands.
4-13. Half-Lives of Chlorinated Compounds in Groundwater, Tutu Wells Site, St. Thomas, U.S.
Virgin Islands.
4-14. Estimated Natural Degradation Rates for Groundwater Contaminants, Tutu Wells Site, St.
Thomas, U.S. Virgin Islands.
4-15. Range of Values for Travel-Time and Natural Degradation of Tetrachloroethene, Tutu
Wells Site, St. Thomas, U.S. Virgin Islands.
5-1. 
Evaluation of NCP Criteria for Soil Remedial Alternatives, Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
5-2. 
Evaluation of NCP Criteria for Groundwater Remedial Alternatives, Tutu Wells Site, St.
Thomas, U.S. Virgin Islands.
5-3. 
Cost Estimate - SRA 1 (No Action/Institutional Controls), Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
5-4. 
Cost Estimate - SRA 2 (Institutional Controls/Capping), Tutu Wells Site, St. Thomas, U.S.
Virgin Islands.
5-5. 
Cost Estimate - SRA 3 (Institutional Controls/Capping/In-Situ SVE [Soil and
BedrockJ/Excavation and Off-Site Disposal), Tutu Wells Site, St. Thomas, U.S. Virgin
Islands.
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GERAGHTY<S? MILLER, INC. 
TUT 
°°7 
1966
TABLES (continued)
5-6. 
Cost Estimate - SRA 4 (Institutional Controls/Capping/Ex-Situ SVE/Excavation and On-
Site Disposal), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
5-7. 
Cost Estimate - SRA 5 (Institutional Controls/In-Situ SVE [Bedrock]/Excavation and Off-
Site Disposal), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
5-8. 
Cost Estimate - GRA 1 (No Action/Institutional Controls), Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
5-9. 
Cost Estimate - 
GRA 2 
(Institutional 
Controls/Source 
Containment/POET
Systems/Treatment/Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
5-10. Cost Estimate - GRA 3 (Institutional Controls/Plume Containment/Treatment/Discharge),
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
5-11. Cost 
Estimate 
- 
GRA 
4 
(Institutional 
Controls/Source 
and 
Plume
Containment/Treatment/Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
5-12. Cost Comparison of Remedial Alternatives, Tutu Wells Site, St. Thomas, U.S. Virgin
Islands.
5-13. 
Summary of Comparative Analysis of Preferred Remedial Alternatives for Soil and
Groundwater, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
FIGURES
1-1. 
Site Location, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
1-2. 
Property Locations, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
2-1. 
Base Map with Topographic Contours, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
2-2. 
Overburden Thickness, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
2-3. 
Groundwater Contour Map, Shallow Bedrock Wells, May 23 to 24, 1994, Tutu Wells
Site, St. Thomas, U.S. Virgin Islands.
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GERAGHTY & MILLER, INC. 
TUT 
°07 
1967
XI
FIGURES (continued)
2-4. 
Groundwater Contour Map, Deep Bedrock Wells, May 23 to 24, 1994, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
4-1. 
Soil Impacted with BTEX and VOCs above Soil Screening Levels, Curriculum Center
(Former Laga Facility), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
4-2. 
Soil Impacted with BTEX above Soil Screening Levels, Ramsay Motors, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
4-3. 
Soil Impacted with BTEX above Soil Screening Levels, Texaco Tutu Service Station,
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
4-4. 
Soil Impacted with PCBs and Manganese above USEPA Risk Assessment Values, Tillett
Gardens, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
4-5. 
Soil Impacted with BTEX above Soil Screening Levels, Adjacent to the Western Auto
Facility, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
4-6. 
Soil Impacted with BTEX and VOCs above Soil Screening Levels, Esso Tutu Service
Station, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
4-7. 
Soil Impacted with VOCs above Soil Screening Levels, OHenry Dry Cleaners, Tutu Wells
Site, St. Thomas, U.S. Virgin Islands.
4-8. 
Capture Zones of Proposed Source Control Plans for BTEX Constituents, Tutu Wells She,
St. Thomas, U.S. Virgin Islands.
4-9. 
Projected Capture Zones for Groundwater Remedial Alternative GRA 4, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
4-10. Generalized Combined Capture Zones, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
4-11. Schematic of Groundwater Treatment Option for Discharge to Surface Water, Tutu Wells
Site, St. Thomas, U.S. Virgin Islands.
5-1. 
Conceptual Layout of Proposed Groundwater Remedies, Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
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GERAGHTY & MILLER, INC. 
TUT 
°07 
196S
Xll
APPENDICES
A. 
Summary of Design Assumptions for Potable Water Discharge Cost Estimate.
B. 
Summary of Capture Zone Analyses.
C. 
Summary of Design Assumptions for Soil and Groundwater Remediation Cost Estimates.
D. 
List of Acronyms and Abbreviations.
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GERAGHTY & MILLER, INC.
TUT 
007 
1969
SECTION 1
DRAFT FINAL
FEASIBILITY STUDY
TUTU WELLS SITE
ST. THOMAS, U.S. VIRGIN ISLANDS
1. INTRODUCTION
In December 1989, Geraghty& Miller, Inc. was retained by the Tutu Environmental
Investigation Committee (TEIC), which consists of Texaco Caribbean, Inc. (Texaco) and Esso
Standard Oil, U.S.A., Inc. (Esso), to prepare a work plan for the investigation of two automotive
service stations and the surrounding area in Tutu, Anna's Retreat, St. Thomas, U.S. Virgin Islands
(USVI) (see Figure 1-1). Following discussions with the United States Environmental Protection
Agency (USERA), Geraghty& Miller submitted the revised Tutu Service Station Investigation
Work Plan (Work Plan) in March 1992 (Geraghty& Miller, Inc. 1992a). This work plan was
incorporated by reference into an Administrative Order by Consent (AOC) (No. H-RCRA-7003
and 9003-92-0401) dated February 19, 1992, with an effective date of March 4, 1992, that was
f 
^ 
issued to Texaco and Esso by the USEPA-Region n, pursuant to Subtitle I of the Resource
Conservation and Recovery Act (RCRA). The AOC required the implementation of a Remedial
•
Investigation (RI) and a Feasibility Study (FS) (USEPA 1992a).
In April 1992, Technical Memorandum I (Geraghty & Miller, Inc. 1992b) was submitted to
the USEPA. This report provided the results of the preliminary reconnaissance activities described
in the Work Plan (Geraghty & Miller, Inc. 1992a) that were implemented from December 1991
through April 1992. Technical Memorandum H (Geraghty & Miller, Inc. 1993a) was submitted to
the USEPA in May 1993 after completion of the field activities described in the Work Plan for the
Tutu Service Station Investigation. Technical Memorandum n provided a discussion of the field
activities and the hydrogeological data collected, an interpretation of soil and groundwater flow
conditions, the groundwater quality data, the data validation report, and an identification of
remaining data gaps (Geraghty & Miller, Inc. 1993 a). All work performed by Geraghty & Miller
prior to May 1993, including Technical Memoranda I and n, is now referred to as the first phase
/**"*"N 
(Phase I) of the Tutu Wells Site RI. During the summer and fall of 1993, communications between
the USEPA and representatives for other Potentially Responsible Parties (PRPs) resulted in an
GERAGHTY & MILLER, INC 
TUT 
°°7 197i W
1-2
increase in the number of the actively participating PRPs from two to seven, the formation of a
Tutu PRP Committee, and an agreement to enlarge the study area to incorporate the area south of
the Esso Tutu Service Station. Figure 1-2 shows the locations of the various properties at the Tutu
Wells Site.
A Phase n RI Work Plan was submitted to the USEPA in December 1993 (Geraghty &
Miller, Inc. 1993b). The Phase n RI Work Plan provided a summary of individual source
investigations conducted by PRPs at numerous properties throughout the Tutu area, identified data
gaps for the expanded RI study area (referred to as the Tutu Wells Site), and defined a scope of
work to gather the data needed to define the nature and extent of impact to environmental quality
at the Tutu Wells Site. The Phase n RI Work Plan was approved by the USEPA in a March 17,
1994 letter to Ms. Ana Gloria Ramos, former Designated Coordinator for the TEIC, from Ms.
Carol Petersen, USEPA Chief for Region n Superfund New York/Caribbean Branch (USEPA
1994a). The Phase n RI was conducted from March to July 1994 in accordance with the Phase n
RI Work Plan. A draft RI Report was submitted to the USEPA in October 1994; the draft RI
Report provided the data collected during Phase n of the RI and included an evaluation of site
conditions based on the large body of data collected by several investigators. USEPA comments
on the draft RI Report were provided in a December 28, 1994 letter to Mr. John McBumey of de
maximis, inc., current Designated Coordinator for the TEIC (USEPA 1994b). A draft Final Phase
H RI Report, dated January 31, 1995, was submitted to the USEPA on February 1, 1995. The
Final Phase H RI Report (RI Report), dated April 6, 1995, was submitted to the USEPA on April
7, 1995 (Geraghty & Miller, Inc. 1995).
In conformance with the AOC and as presented in the Phase U RI Work Plan, Geraghty &
Miller has prepared this FS Report as a companion to the RI Report.
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GERAGHTY & MILLER, INC. 
TUT 
°07 
1972
1-3
1.1 PURPOSE OF THE FEASIBILITY STUDY
The purpose of this FS is to screen areas that may require remedial action, to identify
remedial alternatives, and to assemble information to support the selection of soil and groundwater
remedies that are best suited for the remediation of environmental impacts documented at the Tutu
Wells Site.
Procedures and criteria used in this FS were designed to select the most environmentally
sound, technically feasible, and cost-effective remedial action alternative for the site. This was
accomplished through a phased approach wherein identification and screening of remedial
technologies and process options were carried out concurrently with the RI site characterization
(Geraghty & Miller, Inc. 1995). Subsequent phases consisted of development of alternative
remedies, screening of the alternative technologies, detailed analysis of remedial alternatives, and
comparative analysis of remedial alternatives. Development, screening, and analysis of remedial
alternatives are the principal focus of this FS Report.
1.2 ORGANIZATION OF THE FEASIBILITY STUDY REPORT
The FS Report format is consistent with the format suggested by the USEPA (USEPA
1988a). Incorporated into this FS Report are pertinent data from previously submitted deliverables
(Geraghty & Miller, Inc. 1995). The results of the Tutu Wells Site FS are provided in six sections
and three appendices. One section provides references, and one appendix contains acronyms. Site
characterization data were obtained from the RI Report (Geraghty & Miller, Inc. 1995). The
Baseline Risk Assessment report for the Tutu Wells Site was prepared by a USEPA contractor
(Camp, Dresser & McKee [CDM] Federal Programs Corporation 1995a). Soil screening levels
(SSLs) based on site-specific soil leaching estimates (CDM Federal Programs Corporation 1995b)
were provided by the USEPA for use in the Final FS Report.
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This FS Report is organized as follows:
Section 1.0 
Introduction
Section 2.0 
Summary of Remedial Investigation Results
Section 3.0 
Remedial Action Goals and General Response Actions
Section 4.0 
Identification and Screening of Remedial Technologies
Section 5.0 
Development and Screening of Remedial Alternatives
Section 6.0 
Pre-Design Activities
Section 7.0 
References
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2. SUMMARY OF REMEDIAL INVESTIGATION RESULTS
The RI Report identified the presence of chlorinated volatile organic compounds (VOCs)
and petroleum hydrocarbons in the soil and groundwater at the Tutu Wells Site. The principal
findings are summarized in this section. The comprehensive results are presented in detail in the RI
Report (Geraghty & Miller, Inc. 1995).
2.1 SITE BACKGROUND
Summarized below is information about the site, including a description of the site location
and physical setting with respect to topography, demographics, geology, and hydrogeology, a
summary of the site history; a discussion of the nature and extent of contamination and
contaminant fate and transport; and the results of the baseline risk assessment. This information is
presented in greater detail in the RI Report (Geraghty & Miller, Inc. 1995) and in other site
characterization documents.
2.1.1 Site Description. Geology, Hvdrogeology. and Aquifer Characteristics
The physical setting of the Tutu Wells Site, including the topography, demographics,
geology, and hydrogeology, was described in detail in the RI Report. This section presents a brief
description of these physical characteristics as they pertain to the FS.
2.1.1.1 Description
The Tutu Wells Site is located within the Turpentine Run surface drainage basin, which
occupies approximately 3.4 square miles in east-central St. Thomas (Figure 1-1). The Turpentine
Run Basin is separated into an upper and lower basin. The Tutu Wells Site is located in the upper
basin, which covers approximately 2.3 square miles. The lower basin covers 1.1 square miles
(Jordan and Cosner 1973).
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The Turpentine Run Basin trends north-south and is surrounded by relatively steep slopes.
Other valleys in the area, such as the valley south of the Virgin Islands Housing Authority (VIHA)
and the Curriculum Center (along which Route 384 runs), and the valley just west of the Benjamin
Oliver School, trend northeast-southwest (see Figure 2-1). Land surface elevations along the
Turpentine Run decrease from about 200 feet above mean sea level (msl) at the northern end of the
site to approximately 100 feet above msl at the southern end of the site.
The Turpentine Run is an intermittent stream that traverses the length of the basin. In the
upper Turpentine Run Basin, the stream generally flows from north to south following Route 38.
In the lower basin, the stream turns around Mt. Zion and then trends southeast. Surface-water
runoff is collected in a storm-water catchment system. Storm water and secondary sewage
eventually discharge to the Turpentine Run. The Turpentine Run is partially channelized and
ultimately discharges into Mangrove Lagoon and the Caribbean Sea.
According to the most recent census data (U.S. Census Bureau 1990), approximately
9,100 people live in the Tutu subdistrict of St. Thomas. The Tutu subdistrict, also known as
Anna's Retreat, covers 1.5 square miles (4 square kilometers) in the central-eastern part of St.
Thomas. Tutu is second to Charlotte Amalie in population density on St. Thomas and contains
approximately 20 percent of the island's population.
Several two-lane paved roads, including Route 384, Route 38, and Highway 382, are
located in the Tutu Wells Site. Various commercial establishments line these major roads,
including shopping centers and stores, auto service stations, churches, and office buildings. Private
homes (approximately 300) and multi-family housing, such as the VIHA buildings, generally
occupy the less heavily traveled roads. At least three schools are also located within the Tutu
Wells Site; these include an elementary school (the Seventh Day Adventist School) to the
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northeast, Gomez Junior High School to the northwest, and the Benjamin Oliver School to the
east. Overall, approximately 50 percent of the land area is developed (with buildings and parking
areas) and 50 percent is covered with soil and vegetation.
2.1.1.2 Geology
The surficial unconsolidated materials at the Tutu Wells Site consist of thin deposits of
artificial fill and stream-transported sediments, which in some places overlie older Quaternary
alluvial and colluvial deposits. The unconsolidated deposits overlie volcanic rock. On hills, steep
slopes, and artificial cuts on the hillside, bedrock is exposed at land surface.
Geraghty & Miller's drilling programs have established that most of the shallow sediment
under paved areas of the site consist of fill material and reworked native sediment. Along the axis
of the valley, these sediments are underlain by Quaternary alluvial and colluvial deposits that appear
to thicken southward. The alluvial and colluvial deposits present in the upper basin are relatively
thin, with thicknesses usually varying from 0 to 2 feet, although thicknesses as great as 10 to 30
feet have been observed in isolated valley areas. 
The unconsolidated deposits consist of
unstratified, poorly sorted mixtures of clay, silt, sand, gravel, cobbles, and boulders transported
from the upper valley and the foothills by gravity and flash floods.
The alluvium/colluvium is underlain by moderately weathered, fractured volcaniclastic rock
in which, in some areas, the original rock components have been partially replaced by clay, chlorite,
and oxide minerals (Geraghty & Miller, Inc. 1995). The unconsolidated deposits grade downward
into weathered bedrock, and the transition from unconsolidated deposits to weathered bedrock can
be difficult to discern during drilling.
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The bedrock usually consists of a gray to greenish-gray volcaniclastic tuff and breccia,
with a fine-grained matrix and occasional clasts, ranging in diameter from 1 to 5 centimeters (cm).
Visible mineral grains in the matrix include plagioclase, pyroxene, epidote, hornblende, and
chlorite. At some locations, a coarse-grained volcanic breccia-debris flow underlies the finer
grained tuffs and breccias. The debris flow consists of poorly sorted breccia, slump blocks, and
cobbles up to 20 cm in diameter (Geraghty & Miller, Inc. 1995).
The thickness of the overburden at the Tutu Wells Site varies from 0 to a maximum of 30
feet in some localities (see Figure 2-2). Overburden is thickest along the axis of the Turpentine
Run valley (in which Route 38 generally lies) and thinnest on valley slopes and hilltops. The
thickness of weathered bedrock varies from 0 to approximately 6 feet. No consistent relationship
was observed between weathered bedrock thickness and overburden thickness.
Based on a review of lithologic descriptions and blow counts recorded on available drilling
logs, the overburden in the northern portion of the Tutu Wells Site (near the Curriculum Center)
ranges in thickness from 2 to 5 feet. This area is a topographic high and the weathered bedrock is
generally thin.
In the Turpentine Run valley, in the vicinity of the Texaco Tutu Service Station, the
overburden thickness increases from approximately 2.5 feet along the valley edge (Monitoring Well
TT-3D) to 16.5 feet within the valley (at Monitoring Well TT-1D). The thickness of weathered
bedrock in this vicinity is approximately 6 feet.
At Four Winds Plaza, the overburden increases in thickness from approximately 3 feet (at
Monitoring Well MW-2) to 30 feet (at Monitoring Well CHT-4). The weathered bedrock is less
than 5 feet thick in this vicinity. Near the Esso Tutu Service Station, the overburden is between 5
and 29 feet thick, with generally thicker overburden in the southern and southwestern portions of
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the Esso property. Weathered bedrock was observed at a depth of 2 to 3 feet in the northeastern
portion and of 12 to 14 feet at the southern portion of the Esso Tutu Service Station. Examination
of available drilling logs indicates that the overburden at the Tom Cat Laundry and OTJenry Dry
Cleaners is between 10 and 24 feet thick.
2.1.1.3 Hydrogeology
The regional direction of groundwater flow in the Turpentine Run Basin is toward and
down the axis of principal valleys, with a primary southward direction. In the southern part of the
study area, there is a southeast component of groundwater flow (Graves and Gonzales 1988;
Geraghty & Miller, Inc. 1995). Groundwater in the Turpentine Run Basin occurs in two aquifers
(Jordan and Cosner 1973). The primary aquifer is the fractured volcanic rock of the Water Island
and Louisenhoj Formations and, locally, the Cabes Point Conglomerate. The secondary aquifer
consists of the alluvial deposits in the lower Turpentine Run Basin. The Tutu Wells Site is located
in the upper Turpentine Run Basin. Very thin alluvial deposits are also present in the upper basin,
with thicknesses varying from less than 2 feet to 30 feet in isolated valley areas. However, these
deposits do not constitute an aquifer capable of supplying useable amounts of water because of
their limited areal extent and thickness, and because these deposits are often unsaturated. Most of
the alluvial deposits, where saturated, may be hydraulically connected to the fractured volcanic
rock. Saturated alluvial deposits most commonly occur where bedrock surfaces were incised by
former streams and later filled with sediments or fill. An exception to this condition was observed
at Western Auto, where alluvial deposits were only saturated in a perched zone within a gravel
layer overlying a clay layer.
Groundwater in both units generally exists under unconfined (or water-table) conditions.
Localized low permeability (fine-grained) layers in the alluvial deposits may result in perched water
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and possible confined bedrock conditions of limited extent. The bedrock aquifer may be partially
confined in places by zones of relatively unfractured shallow rock.
Groundwater is stored and transmitted in fractures in the bedrock, which behaves as an
unconfined aquifer. The water table occurs at depths of 5 to 106 feet below land surface (bis), with
the greater depth to water generally occurring beneath ridges and hilltops (Geraghty & Miller, Inc.
1995). Since the groundwater is transmitted principally through fractures and the rock is more
fractured along major lineaments, the aquifer demonstrates vertical, as well as horizontal,
anisotropy.
In the study area, groundwater supply is derived from wells installed in the fractured
volcanic rock. Supply well depths in the upper basin range from 73 to 325 feet bis (Stevens et al.
1981). The depths of these wells do not correlate with yield, but rather are an indication of where
water-bearing fracture zones were penetrated. Short-term well yields in the upper basin range as
high as 100 gallons per minute (gpm); sustained yields range between 2 and 21 gpm (Jordan and
Cosner 1973).
Very little precipitation reaches the saturated zone as groundwater recharge. On St.
Thomas, evapotranspiration may consume 95 percent or more of the incident rainfall (Jordan and
Fisher 1977). The small fraction of precipitation that is not lost to evapotranspiration or storm-
water runoff percolates downward through the thin overburden, or where overburden is not
present, directly into the interconnecting network of fractures that transect the rock.
Recharge to the fractured volcanic rock in the upper basin results primarily from occasional
major rainstorms and is dependent on the frequency and volume of rainfall. As a result of surface
runoff and a high evapotranspiration rate, rainfall of at least 2 inches within a 24-hour period is
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necessary for recharge to occur. Annual recharge to the upper basin due to rainfall is estimated to
be 130 million gallons (Jordan and Cosner 1973).
The bottom of the Tutu aquifer is not well defined. The physical bottom of the aquifer is
the depth at which the fracture intensity diminishes and the fractures are no longer sufficiently
interconnected to allow for significant groundwater flow. No information is available to indicate at
what depth this phenomenon occurs. Chemically, the bottom of the aquifer could be defined by the
transition from groundwater of natural chemistry acceptable for consumption to more mineralized
water that can no longer be feasibly used or treated for public or commercial supply. There is
limited evidence that groundwater below a depth of about 300 feet in the central and northern
portion of the Tutu area is relatively mineralized connate water (Geraghty & Miller, Inc. 1983). In
the southern portion of the Tutu area, the freshwater/saltwater interface may occur at shallower
depths.
In the bedrock aquifer, three general zones (or depths) are monitored by the existing wells.
The shallow monitoring wells monitor the zone extending approximately 8 to 10 feet below the
water table. The deep monitoring wells monitor the zone from 30 to 50 feet below the water table,
and the supply wells monitor the entire thickness of the aquifer. The supply wells were grouped
with the deep monitoring wells for data interpretation.
Groundwater flow in the shallow zone is generally toward the south. Water-level
measurements collected from shallow wells on May 10 and 23, 1994 during the Phase n RI were
used to construct water-level contour maps (Geraghty & Miller, Inc. 1995). Figure 2-3 shows the
shallow groundwater flow conditions measured on May 23, 1994. As shown on this figure, the
shallow groundwater flow from the east and west converges beneath Route 38, toward what
appears to be the axis of the Turpentine Run Basin. One of the principal fractures identified is
oriented along Route 38 (CDM Federal Programs Corporation 1992); this fracture zone appears to
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act as a shallow groundwater discharge zone. The former stream channel of the Turpentine Run
has been filled, and surface drainage is channelized through a storm sewer under the area.
Shallow groundwater flow is characterized by a steep hydraulic gradient. This steep
gradient is indicative of the low overall permeability of the zone penetrated by the shallow wells.
The gradient is less steep in the area that includes the Texaco Tutu Service Station and the north
portion of the Four Winds Plaza parking lot, indicating that the shallow zone has a higher
permeability in this area. This observation agrees with the information collected during well
development. Monitoring Wells MW-3, MW-4, and MW-6R could sustain pumpage at rates of
approximately 2 gpm, whereas most other shallow monitoring weDs went dry when pumped for
relatively short periods of time. The hydraulic gradient of the shallow portion of the aquifer
steepens again in the vicinity of the Esso Tutu Service Station. Monitoring wells at and near the
Esso Tutu Service Station have been pumped dry during well development and groundwater
sampling.
Water levels measured in deeper monitoring wells on May 10 and 24, 1994 during the
Phase n RI were used to construct water-level contour maps. Figure 2-4 shows deep groundwater
flow conditions measured on May 23, 1994. This map indicates that the general gradient of
groundwater flow in the deeper zone at the Tutu Wells Site is to the south, with a southeast
component in the southern part of the study area. In the northern portion of the site near
Monitoring Well MW-6D, a more gentle gradient indicates that the more permeable zone in the
shallow bedrock also extends downward into the deeper monitored portion of the bedrock.
In general, there is a small downward vertical hydraulic gradient throughout most of the
study area. A slight upward gradient was observed in 1994 in mid-May and mid-June in the
northeastern portion of the Tutu Wells Site in Monitoring Wells MW-13/MW-13D. This upward
gradient may be attributed to the slow recovery of Monitoring Well MW-13 after it was developed
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in May 1994. Pumpage of supply wells at the VTHA complex may increase the downward vertical
hydraulic gradient in the northeastern portion of the Tutu Wells Site, which may explain the steep
downward gradient observed at Monitoring Wells MW-13/MW-13D on July 20, 1992. As
expected, a generally horizontal or slightly upward gradient is present near the former stream
channel of the Turpentine Run (Monitoring Wells MW-6R/MW-6D). A predominantly downward
gradient was observed in the Upper Turpentine Run Basin at Wells MW-1/MW-lD, TT-1/TT-1D,
MW-4/MW-4D, MW-8/DW-1, MW-10/MW-10D, and SW-6/DW-2. Based on water-level
measurements made in these wells on May 24, 1994, the steepest downward vertical gradient was
observed at Monitoring Wells MW-20/MW-20D. However, this steep downward gradient may be
a result of the incomplete recovery of Monitoring Well MW-20D, which had been developed 1
week earlier.
2.1.1.4 Summary of Aquifer Hydraulic Characteristics
Based on the evaluation of the data presented in the RI Report (Geraghty & Miller, Inc.
1995), the following conclusions have been developed:
• 
Zones of fracture have a controlling influence on the vertical and horizontal distribution
of aquifer permeability and transmissivity. The highest transmissivity zones are located
along the major fractures, particularly where major fracture zones intersect (e.g., in the
northern part of the Four Winds Plaza parking lot). Transmissivity values calculated
from wells located in this area ranged from approximately 20,400 to 90,500 gallons per
day per foot (gal/day/ft), with hydraulic conductivities of approximately 70 to 300
gallons per day per square foot (gal/day/ft2). In comparison, transmissivity values
calculated from wells not located in the major fracture zones range from approximately
900 to 2,300 gal/day/ft (with hydraulic conductivities of approximately 3 to 7.7
gal/day/ft2) (Geraghty & Miller, Inc. 1995).
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• 
Based on the pumping tests of the Eglin HI Supply Well, the aquifer's response to the
pumpage of deep supply wells appears to be anisotropic in both the vertical and
horizontal direction. Drawdown is greater in deep bedrock observation wells located
along major fractures than in directions perpendicular to the orientation of those
fractures.
• 
Based on the pumping tests of the Eglin HI Supply Well, pumpage at a constant rate of
approximately 31 gpm creates a zone of influence oriented northwest-southeast. The
northeast-southwest extent of the zone of influence is approximately 500 feet and the
northwest-southeast extent is approximately 1,045 feet (Geraghty & Miller, Inc. 1995).
2.1.2 History of Known Public Concerns
In 1982, Geraghty & Miller was retained by the US VI Department of Conservation and
Cultural Affairs (DCCA) to inventory the groundwater resources of St. Croix, St. Thomas, and St.
John and prepare a groundwater management plan for the USVI. As part of this program,
sampling activities were carried out in the Turpentine Run Basin. These activities included an
aquifer pumping test of the VIHA Well No. I (VIHA I). After 5 hours of pumping, Geraghty &
Miller collected a groundwater sample on May 20, 1982 from the VIHA I supply well for analysis
of USEPA priority pollutant organic compounds. The sample was sent to the USEPA in Edison,
New Jersey, where it was forwarded to Mead CompuChem Laboratories in Research Triangle
Park, North Carolina (Geraghty & Miller, Inc. 1983).
Chlorinated VOCs were detected in the VIHA I groundwater sample. Those constituents
included 1,2-dichloroethene (1,2-DCE) at a concentration of 12 micrograms per liter (ug/L)
(equivalent to parts per billion [ppb]), 55 ug/L of tetrachloroethene (PCE), and 10 ug/L of
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trichloroethene (TCE) (Geraghty & Miller, Inc. 1983). At that time, drinking water standards for
these VOCs had not been established by the USEPA. In a report submitted to the DCCA,
Geraghty & Miller recommended further investigation to identify the source of these chlorinated
VOCs (Geraghty & Miller, Inc. 1983).
In July 1987, Mr. Eric Tillett, owner of Tillett Gardens, contacted the US VI Department of
Planning and Natural Resources (DPNR) regarding an odor emanating from his well water.
Representatives of the USEPA and its Technical Assistance Team (TAT) subsequently performed
groundwater sampling at the Tillett well and six additional commercial wells located in Turpentine
Run. The analytical results from this sampling event indicated that the Tillett well contained
gasoline constituents and chlorinated VOCs, and that the other six commercial wells also contained
elevated levels of chlorinated VOCs. Based on these results, the DPNR declared that an eminent
health threat existed that could affect approximately 20,000 people living in St. Thomas and an
indefinite number of tourists who vacation in St. Thomas.
Based on groundwater sampling results, the DPNR closed 13 commercial and five private
wells in the Tutu area between July and September 1987 (USEPA 1991 a). Many of these wells
are currently in use for non-potable purposes. After the initial sampling of the six supply wells in
July 1987, the USEPA's TAT sampling and screening analysis was expanded to include 24 supply
wells, beginning in August 1987. Analyses for benzene, toluene, PCE, TCE, and 1,2-DCE were
performed using a Photovac portable field gas chromatograph (GC) on samples collected monthly
from August through December 1987. Photovac analyses were also performed on samples
collected in January, February, May, August, and November 1988 and February, May, and August
1989 (Weston/Spill Prevention and Emergency Response [SPER] 1989).
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Selected groundwater samples were submitted for laboratory analysis for VOCs during
these various sampling events. The PCE concentration in the Harvey supply well was 7,600 ug/L
in August 1987 (Westem/SPER 1988).
In October 1987, groundwater samples were also analyzed for Hazardous Substance List
(HSL) VOCs, base neutral and acid extractable compounds (BNAs), and metals by USEPA-
contracted laboratories. Fourteen of the 24 supply wells sampled during this event had elevated
values of VOCs, including trans-l,2-DCE, TCE, PCE, toluene, benzene, and methyl tertiary-butyl
ether (MTBE). The October 1987 sampling event confirmed the August 1987 groundwater VOC
sampling results and also detected arsenic (IS ug/L), selenium (15 ug/L), and zinc (460 ug/L) in
some of the wells sampled (Weston/SPER 1988). The highest reported contaminant concentration
for the October 1987 sampling event (excluding methylene chloride, which is a common laboratory
contaminant) was 2,000 ug/L of PCE in the Harvey Supply Well sample (Weston/SPER 1988).
Laboratory analyses for HSL VOCs, BNAs, metals, and cyanide were performed on 18
supply well samples collected in November 1988 (Weston/SPER 1989). The USEPA also
sampled and analyzed 123 cisterns that were filled with groundwater pumped from supply wells
located in this area. Three of the cisterns contained total VOCs in excess of 1,000 ug/L (USEPA
1991a).
In January 1988, the USEPA initiated a limited Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) removal action that included the decontamination and
cleaning of five residential cisterns contaminated by hazardous substances, modification of
plumbing, delivery of water by tank trucks as a temporary alternative water supply, and
implementation of a well-water monitoring program (USEPA 199 la).
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On November 6, 1988, the USEPA sent Esso, OHenry Dry Cleaners, and Texaco an
information request letter under Section 104(e) of CERCLA and 3007 of RCRA regarding
operations and waste containment and disposal at the Esso and Texaco Service Stations and the
OHenry facility. Based on the findings of this request, the USEPA issued a unilateral
Administrative Order (AO) under CERCLA and RCRA on March 22, 1990 to Texaco, Esso, and
OHenry (USEPA 1990). This AO required these parties to assume the USEPA's well-water
monitoring program, to provide potable water to residents with contaminated well water, and to
coordinate and design plans to connect those residents to the public water supply.
In June 1989, the USEPA-Region n sent Texaco and Esso a draft AOC requiring the
implementation of an RI in the Tutu area. Texaco and Esso formed the TEIC in March 1990 and
retained Geraghty & Miller to prepare a work plan for, and to implement, the Tutu Service Station
Investigation, which is now referred to as Phase I of the RI. A final AOC was entered into by the
USEPA, Texaco, and Esso in February 1992 (USEPA 1992a).
In August 1991, the USEPA presented its Hazard Ranking System (HRS) document for
the Tutu Wells Site (USEPA 199la). In this document, at least nine PRPs were identified as
known or potential sources of groundwater contamination. These PRPs include, from north to
south, the VIHA, the Curriculum Center (former Laga facility), Ramsay Motors, Antilles Auto
Parts, Texaco Tutu Service Station, Tillett Gardens, Esso Tutu Service Station, OHenry Dry
Cleaners, and Rodriguez Auto Parts (see Figure 1-2). Preliminary site assessments had been
conducted at these properties by USEPA subcontractors. The Western Auto facility, which was
investigated during Phase n activities by Geraghty & Miller and others, was not included in the
HRS or preliminary site assessments.
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2.2 NATURE AND EXTENT OF CONTAMINATION
The nature and extent of contamination was described in detail in the RI Report (Geraghty
& Miller, Inc. 1995). This section provides a summary of environmental impacts to soil and
groundwater quality.
2.2.1 Soil Quality
Soil sampling and soil-gas surveys were conducted during Phases I and II of the RI to
identify the areas of impacted soil and to evaluate the nature and extent of impact to soil and
groundwater quality. In addition, Geraghty & Miller compiled historical information and recent
data from properties where independent investigations by other technical consultants were
performed. These data are summarized in the RI Report (Geraghty & Miller, Inc. 1995).
Soil samples collected during the RI were analyzed for target compound list (TCL) VOCs,
TCL BNAs, target analyte list (TAL) metals, cyanide, and/or total petroleum hydrocarbons (TPH).
The USEPA directed the TEIC to use the USEPA's vadose zone modeling SSLs for BTEX and
chlorinated VOCs as guidance values to identify areas that may require remediation of soils (CDM
Federal Programs Corporation 1995b). These guidance values were developed specifically for the
Curriculum Center (former Laga Building), Texaco Tutu Service Station, Esso Tutu Service
Station, and OHenry Dry Cleaners (CDM Federal Programs Corporation 1995b), and are
provided in Table 2-1. Chemicals of concern (COCs) at the Tutu Wells Site were limited mainly to
BTEX and chlorinated VOCs. TCL BNAs, such as polycyclic aromatic hydrocarbons (PAHs),
were not considered COCs because (1) PAHs and other contaminants which were not detected in
groundwater above MCLs, are not considered to be of concern for soils, (2) these contaminants
are not generally very mobile, and (3) no direct exposure risks associated with these contaminants
were identified in the Baseline Risk Assessment (CDM Federal Programs Corporation 1995a).
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As directed by the USEPA, the potential need for soil remediation at the remaining
properties within the Tutu Wells Site was determined using the guidance values provided for the
Esso Tutu Service Station because the subsurface conditions at the Esso Tutu Service Station are
representative of conditions throughout the Tutu Valley Building. Different guidance levels were
developed by the USEPA for shallow and deep soil at each property, based on the vertical distance
to the water table (see Table 2-1). The SSLs are considered as "to-be-considered" (TBC) criteria.
These guidance levels will be referred to as SSLs, and these SSLs are further discussed in Section
3.1.2 (Preliminary Remedial Goals).
Exceedances of the USEPA's SSLs (CDM Federal Programs Corporation 1995b) for
organic compounds were used as one of two criteria to determine if sites may require soil
remediation. The second criterion used to identify areas that may require soil remediation included
the USEPA-approved risk assessment of soil quality (CDM Federal Programs Corporation 1995a).
Tables 2-2 and 2-3 provide summaries of the USEPA risk assessment soil quality threshold values
for carcinogenic and non-carcinogenic risks, respectively. 
COCs were detected at several
properties at concentrations below the USEPA's SSLs, indicating that releases of these constituents
had potentially occurred, although the residual concentrations do not currently represent a threat to
human health, groundwater, or the environment. At these locations, organic compounds were
detected in soil gas and shallow soil above 10 ug/kg, indicating that releases had occurred. In
addition, the presence of significant concentrations of these COCs in groundwater at these
properties indicates that contaminants may be present at higher concentrations in soil and fractures
in the unsaturated bedrock, which was not sampled.
For the Tutu WeUs Site, the USEPA directed that soil be considered to be potentially
impacted by metals and other inorganic compounds if the analytical result exceeded two times the
average background value. It should be noted that the metal concentrations detected in soil at the
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Tutu Wells Site are probably all present naturally and are not the result of operational history. In
addition, metals do not partition to an appreciable degree into the aqueous phase. Therefore, any
potential impact from metals would be from dermal contact or inhalation of dust. A complete
evaluation of the potential impact of metals in soil through inhalation of dust or dermal contact is
presented in the final baseline risk assessment prepared by CDM (CDM Federal Programs
Corporation 1995a). The exposure assessment prepared by CDM indicated that metal
concentrations at the individual properties do not pose a risk through contact or inhalation, with
the possible exception of manganese at the Tillett property (CDM Federal Programs Corporation
1995a).
Based on the USEPA's SSLs (CDM Federal Programs Corporation 1995b), the properties
with soil impacted by organic compounds include the Curriculum Center (former Laga building),
Ramsay Motors, Texaco Tutu Service Station, Western Auto, Esso Tutu Service Station, and
CXHenry Dry Cleaners (see Figure 1-2). Based on the USEPA subcontractor's risk assessment, the
Tillett property is the only other property that may require soil remediation. Manganese and
Aroclor 1242 (a polychlorinated biphenyl [PCB]) were found to be above the acceptable site-
specific carcinogenic risks and the non-carcinogenic hazard quotient of 1 in surface soil at Tillett
Gardens (CDM Federal Programs Corporation 1995a). Appropriate remedial measures may be
required at this property (see Section 2.4 [Baseline Risk Assessment]).
The properties identified with soil concentrations above the USEPA's SSLs (CDM Federal
Programs Corporation 1995b) were placed into the following two categories: properties with soil
impacted by chlorinated VOCs, and properties with soil impacted by petroleum-related compounds
including benzene, toluene, ethylbenzene, and xylene (BTEX).
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2.2.1.1 Chlorinated VOCs in Soil
Chlorinated VOCs have been found in soil at various properties throughout the Tutu Wells
Site. Based on the exceedance of USEPA's SSLs for chlorinated constituents, the Curriculum
Center, Esso Tutu Service Station, and OHenry Dry Cleaners were identified as having chlorinated
VOC impacts to soil (see Table 2-4). The primary chlorinated VOCs include PCE, TCE, 1,2-
DCE, l,l,l-trichloroethane(l,l,l-TCA), and l,l-dichloroethane(l,l-DCA).
At the Curriculum Center, PCE was detected in eight soil samples at the north-central side
of the building in the vicinity of the former discharge pipe and alleged former waste pit, at
concentrations ranging from approximately 3 to 180 micrograms per kilogram (ug/kg). TCE was
detected in four soil samples at estimated concentrations ranging from U to 130J ug/kg. 1,1,1-
TCA was detected in Soil Sample TWS-03 above the USEPA SSL. No other chlorinated VOCs
were detected at the Curriculum Center. Although only one soil sample was reported above the
USEPA's SSL for chlorinated VOCs, higher concentrations may be present in the soil beneath the
building or in the unsaturated bedrock, which was not sampled. This interpretation is based on the
very high soil gas results recorded during a soil gas survey conducted at the Curriculum Center in
February and March 1994 (Geraghty& Miller, Inc. 1995) and on the high chlorinated VOC
concentrations found in groundwater at the Curriculum Center. 
These concentrations, in
conjunction with a very steep concentration gradient, suggest that chlorinated VOCs may be
present as dense non-aqueous phase liquids (DNAPLs) in the fractures of the unsaturated and/or
saturated bedrock.
At the Esso Tutu Service Station, PCE, TCE, 1,1,1-TCA, 1,2-DCE, and 1,1-DCA were
detected above the USEPA's SSLs in four soil samples with individual chlorinated VOC
concentrations ranging from 44 to 3,200 ug/kg (see Table 2-4). These chlorinated VOCs were
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detected in soil samples collected in the western portion of the site, near the north oil/water
separator.
PCE was found in the vicinity of the OHenry Dry Cleaners above the USEPA's SSLs in
seven samples collected from the western portion of the property in concentrations ranging from
200D ("D" indicates value determined by secondary dilution) to 440,000 ug/kg (see Table 2-4).
These detected PCE concentrations in soil indicate that PCE was released near the OHenry Dry
Cleaners. In addition, PCE concentrations greater than 10,000 ug/kg indicate a high possibility that
DNAPL is present (USEPA 1992b). From 1987 to 1991, the PCE concentration in groundwater
collected from the Harvey Supply Well, located downgradient of the OHenry Dry Cleaners, ranged
as high as 7,600 ug/L to 1,500 ug/L. Groundwater concentrations exceeding 1 percent of the
solubility of PCE (1,500 ug/L) are indicative of a high potential for DNAPL in the subsurface
(USEPA 1992b). Considering the historical and continued use of PCE as a dry cleaning solvent at
the OHenry facility and the soil and groundwater PCE concentrations above USEPA threshold
values for identification of DNAPL presence (USEPA 1992b), DNAPL is considered to be present
in the subsurface near the OHenry Dry Cleaners.
2.2.1.2 BTEXinSoil
The USEPA SSLs were exceeded for BTEX at the Curriculum Center, Ramsay Motors,
Texaco Tutu Service Station, Western Auto, and the Esso Tutu Service Station (see Table 2-4). In
addition, Antilles Auto Parts may have contributed to some soil impact at the adjacent Ramsay
Property, based on a previously reported waste oil spill. Similarly, although no constituents were
found above USEPA SSLs at the Four Winds Plaza, potential impacts to soil cannot be ruled out
due to the detection of elevated soil gas concentrations of diesel components.
BTEX compounds exceeded USEPA SSLs at Surface Soil Samples SS-12 and TWS-03
collected at the northeast corner of the Curriculum Center. 
Individual BTEX constituent
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concentrations exceeding the USEPA SSLs ranged from benzene at 2,700 ug/kg to toluene at
500,000 ug/kg.
At the Ramsay Motors property, BTEX compounds were found in two soil samples
located in the vicinity of the underground storage tank (UST). Benzene and ethylbenzene
concentrations were detected above their respective USEPA SSLs. Analytical results included an
estimated concentration of 17 ug/kg of benzene in Soil Sample HB-2, and an estimated
concentration of 190 ug/kg and 290 ug/kg of ethylbenzene in Soil Samples HB-5 and HB-2,
respectively.
At the Texaco Tutu Service Station, BTEX compounds were found in the vicinity of the
former USTs and at the oil/water separator. Two soil samples (Sample OW/SB-1 and TT-ID) and
one field replicate (Sample TT-ID FR) collected at Texaco exceeded the USEPA SSLs for BTEX
constituents. Results for individual BTEX constituents ranged from 69 ug/kg for benzene to 630
ug/kg for ethylbenzene. However, higher BTEX concentrations have been detected in excavated
soil; floating product has been observed; and elevated BTEX concentrations have been detected in
groundwater.
In the vicinity of Western Auto , BTEX constituents were reported in 21 soil samples at
concentrations above the USEPA SSLs (see Table 2-4). USEPA SSLs were exceeded for all
BTEX constituents. Individual BTEX compound concentrations above the USEPA SSLs ranged
from estimated concentrations of toluene at 16 ug/kg and ethylbenzene at 16 ug/kg in Soil Sample
T1-4 to 34,000 ug/kg of xylenes in Soil Sample SS-1. A shallow gravel layer underlying the
pavement in the vicinity of the Western Auto facility contains noticeable oil. Post-excavation
sampling for the UST closure was limited to TPH sample collection and analysis. The lack of more
comprehensive sampling results for the UST closure and the shallow oily gravel layer indicate that
soil volumes estimated for the purposes of this FS Report are preliminary. During pre-design
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activities, further data will be needed to determine the actual volume of soil that may require
remediation.
At the Esso Tutu Service Station, BTEX constituents exceeded USEPA SSLs in 16
samples collected at the site in the vicinity of the pump island, the north oil/water separator, and the
former UST excavation. Individual BTEX concentrations above the USEPA soil cleanup profile
ranged from 26 ug/kg of ethylbenzene to 540,000 ug/kg of xylenes (see Table 2-4).
2.2.2 Groundwater Quality
During the Phase n RI, groundwater samples were collected from 51 monitoring wells and
15 supply wells at the Tutu Wells Site. The samples were analyzed for TCL VOCs, TCL BNAs,
TAL metals, and various inorganic water quality parameters. The sampling confirmed and
supplemented earlier efforts to delineate the horizontal and vertical extent of petroleum-related
compounds (BTEX and MTBE) and chlorinated VOCs (including PCE, TCE, DCE, and vinyl
chloride) in the groundwater at the Tutu Wells Site. The results of the 1994 Phase n RI
comprehensive groundwater sampling event, the Phase I RI monitoring well sampling, and the
results of eight supply well sampling events are discussed in detail in the RI Report (Geraghty &
Miller, Inc. 1995).
2.2.2.1 Chlorinated VOCs
During the Phase I RI, Geraghty & Miller identified two separate chlorinated VOC plumes
(Geraghty & Miller, Inc. 1993a). One plume originated in the vicinity of the Curriculum Center
and was referred to as the northern chlorinated VOC plume. The other plume originated in the
vicinity of OHenry Dry Cleaners and was referred to as the southern chlorinated VOC plume.
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Groundwater data from both the shallow and deep zones were plotted on one figure during Phase I
(Geraghty & Miller, Inc. 1993 a). As part of the Phase n evaluation, data from these zones were
plotted on separate figures to identify trends more clearly. The Phase n RI Report also presented
the data for PCE, TCE, 1,2-DCE, and vinyl chloride on individual maps for both the shallow and
deep zones (Geraghty & Miller, Inc. 1995). The data presented in this manner support the
identification of two separate total chlorinated VOC plumes in excess of 100 ppb, although the
northern plume appeared to be separated into two discrete bodies in both the shallow and deep
zones. In addition, in the shallow zone, the northern and southern chlorinated plumes appear to
have merged, based on the outline of the 10-ppb contour.
The shallow northern chlorinated VOC plume, which originates near the Curriculum
Center, extends approximately 1,600 feet south in the direction of groundwater flow to a point just
southeast of Four Winds Plaza and is approximately 500 feet wide. The highest concentrations of
total chlorinated VOCs occurred in shallow zone monitoring wells, where chlorinated VOC
concentrations greater than 1,000 ppb were detected. The highest concentration was found in
Monitoring Well MW-16 (3,543 ppb) at the Curriculum Center. The primary chlorinated VOCs
detected in the northern plume are 1,2-DCE, PCE, and TCE. Vinyl chloride was also detected at
high concentrations, but only in a few wells. The maximum concentrations of these compounds
were 1,2-DCE at 2,100 ppb and vinyl chloride at 1,300 ppb (in Monitoring Well MW-16), PCE at
360 ppb (in Monitoring Well MW-1D), and TCE at 78 ppb (in Monitoring Well MW-1).
Concentrations of total chlorinated VOCs greater than 1,000 ppb were not detected in any deep
zone wells, but a total chlorinated VOC concentration of 931 ppb was detected in Monitoring Well
MW-1D at the Curriculum Center. Historically, the concentration of PCE in the Tillett Supply
Well, located downgradient of the Curriculum Center, has been reported up to 2,040 ug/L
(Weston/SPER 1988), which exceeds 1 percent of the solubility of PCE. 
Based on USEPA
guidance for DNAPL site characterization (USEPA 1992b), these data suggest the possible
presence of DNAPL in the vicinity of the Curriculum Center.
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The southern plume originates near the OHenry Dry Cleaners and extends southeast
approximately 4,000 feet; h is approximately 800 feet wide. In the shallow zone, the highest total
concentration of VOCs detected in 1994 was 181 ppb in Monitoring Well OHMW-4, which is just
downgradient of OHenry Dry Cleaners. In the deep zone, total chlorinated VOCs were detected
above 100 ppb in the Steele, LaPlace, Smith, and Harvey supply wells at concentrations between
137 and 173 ppb. The maximum concentrations of chlorinated VOCs were PCE at 140 ppb (in
Monitoring Well OHMW-4) and 1,2-DCE at 100 ppb and TCE at 33 ppb (in the Steele Supply
Well). Historically, chlorinated VOC concentrations (primarily PCE) in excess of 1,000 ppb have
been detected adjacent to the OHenry Dry Cleaners at Monitoring Well OHMW-4 (1,400 ppb in
February 1990 and 1,000 ppb in January 1990) and the Harvey Supply Well (7,600 ppb in August
1987). The presence of PCE at concentrations in excess of 1,500 ppb suggests the possible
presence of DNAPL in the saturated zone in the vicinity of the OHenry Dry Cleaners.
2.2.2.2 Petroleum-Related Compounds
Two separate petroleum-related plumes have been delineated at the Tutu Wells Site. One
plume is located near the Texaco Tutu Service Station and was measured to be approximately 400
feet long in its north-south dimension and 200 feet wide in its east-west dimension in 1994. The
highest BTEX concentrations were detected in Monitoring Well TT-1 (58,700 ppb). Individual
BTEX compounds were detected in Monitoring Well TT-1 at the following maximum
concentrations: Benzene at 21,000 ppb, toluene at 16,000 ppb, ethylbenzene at 3,700 ppb, and
xylenes at 18,000 ppb. The highest MTBE concentration detected was in Monitoring Well TT-4
(56,000 ppb). The highest n-propylbenzene concentration was detected in Monitoring Well TT-1
(450 ppb).
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The second petroleum-related plume was located near the Esso Tutu Sendee Station and
was measured to be approximately 200 feet long in its north-south dimension and 150 feet wide in
its east-west dimension in 1994. The highest BTEX concentrations were detected in Monitoring
Well SW-3 (39,300 ppb). BTEX compounds were detected in Monitoring Well SW-3 at the
following maximum concentrations: Benzene at 10,000 ppb, toluene at 3,200 ppb, ethylbenzene at
4,100 ppb, and xylenes at 22,000 ppb. 
MTBE was detected at a maximum concentration of
89,000 ppb in this well.
2.2.2.3 Evaluation of the Potential Presence of Nonaqueous Phase Liquids
The presence of high concentrations of BTEX and chlorinated VOCs in groundwater
indicates that nonaqueous phase liquids (NAPLs) may exist in the unsaturated or saturated zones at
the Tutu Wells Site. NAPLs can either be less dense than water, such that they float on the water
table and are termed light NAPLs (LNAPLs), or they are denser than water and sink through the
aquifer as DNAPLs.
The detection in groundwater of individual chlorinated VOCs at concentrations in excess
of 1 percent of their solubility is a strong indication of the possible presence of phase-separated
chlorinated VOCs, or DNAPLs, below the water table. The possible presence of globules or
droplets of DNAPL in bedrock fractures indicates that there is a potential source of chlorinated
VOCs both in the unsaturated zone and below the water table that will continue to provide
dissolved constituents. There are currently no technologies capable of completely removing
DNAPLs from aquifers, especially in fractured bedrock, and their presence renders complete
aquifer restoration impossible.
The absence of constituents above 1 percent solubility does not preclude the possibility of
free product. For example, direct observations of floating product and sheens in some monitoring
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wells at the Esso Tutu and Texaco Tutu Service Stations confirmed the presence of LNAPLs, but
BTEX concentrations in groundwater samples collected from these wells were not detected above
1 percent of the solubility of these individual compounds.
The solubility of benzene at 25 degrees Celsius (°C) is 1,750 milligrams per liter (mg/L).
Therefore, 1 percent solubility would be 17.5 mg/L or 17,500 ug/L. Based on their solubilities, 1
percent solubility for the other BTEX constituents is 5,350 ug/L for toluene, 1,520 ug/L for
ethylbenzene, and 1,750 ug/L for o-xylene.
The only locations where the concentrations of individual BTEX constituents exceeded 1
percent of the solubility were at Monitoring Wells TT-4 (located at the Texaco Tutu Service
Station) and CHT-3 (located at the Esso Tutu Service Station). At Monitoring Well TT-4,
benzene was detected at 21,000 ug/L, toluene was detected at 17,000 ug/L, ethylbenzene was
detected at 3,300 ug/L, and total xylenes were detected at 17,000 ug/L. Floating product had been
observed in Texaco Tutu Service Station Monitoring Wells MW-4D and MW-5, and product
sheen and/or odors had been noted in Monitoring Wells TT-1, TT-1D, and TT-4.
At Monitoring Well CHT-3, ethylbenzene was found at 1,800 ug/L and total xylenes at
2,000 ug/L. Floating product has never been documented in Monitoring Well CHT-3, but product,
sheen, and/or odors had been reported in Esso Tutu Service Station Monitoring Wells MW-9,
MW-9S, and SW-7. Unlike DNAPLs, LNAPLs can be remediated through pumping and other
technologies.
The current and historical soil and groundwater data for the various properties within the
Tutu Wells Site were reviewed to assess the potential for DNAPL to be present in the subsurface.
Based on this review, there is a moderate to high probability that DNAPL exists beneath the
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OHenry Dry Cleaners and Curriculum Center properties. The following information supports this
conclusion:
• 
The historical use of PCE as a dry cleaning solvent at both locations suggests
the high probability of a DNAPL release (USEPA 1992b).
• 
Concentrations of PCE in soil at the OHenry Dry Cleaners exceed USEPA
SSLs for potential groundwater contaminant source areas.
• 
Samples from the abandoned pipes in the floor of the Curriculum Center
contained 30 percent PCE.
Groundwater samples from wells downgradient of the Curriculum Center and the OHenry
Dry Cleaners contained greater than 1 percent of the solubility of PCE (1,500 ug/L) (USEPA
1992b). For example, from 1987 to 1991, the maximum annual PCE concentration in the Harvey
Supply Well, located downgradient of the OHenry Dry Cleaners, ranged as high as 1,500 to 7,600
ug/L. 
In the Tillett Supply Well, which is downgradient of the Curriculum Center, the
concentration of PCE was as high as 2,040 ug/L on July 22,1987 (Weston/SPER 1988).
Therefore, DNAPL may be present in the vicinity of the Curriculum Center and the
OHenry Dry Cleaners. Due to the shallow depth to bedrock at the Curriculum Center, the release
of DNAPL at this location could result in downward migration of DNAPL into the fractured
bedrock above the water table. Similarly, at the OHenry Dry Cleaners, a release of DNAPL near
the land surface could migrate downward into the soil and weathered bedrock that is present above
the water table.
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2.3 CONTAMINANT FATE AND TRANSPORT
Contaminant fate and transport for soil and groundwater are evaluated in detail in the
Phase n RI Report (Geraghty & Miller, Inc. 1995). Based on the results of soil and groundwater
sampling at the Tutu Wells Site, numerous organic constituents were identified as COCs. To
evaluate potential fate and transport processes for the COCs at the Tutu Wells Site, the physical
and chemical properties of the constituents, the environmental transformation processes affecting
the constituents, and the characteristics of the surrounding environment were examined. The
primary COCs found in the soil and groundwater are chlorinated VOCs and petroleum-related
compounds, primarily BTEX constituents.
The primary route of exposure to human receptors was transport of dissolved COCs in
groundwater to supply wells used for domestic and commercial uses. Secondary exposure routes
include potential ingestion, inhalation, and/or dermal contact with COCs in surficial soil.
2.4 BASELINE RISK ASSESSMENT
A baseline risk assessment for the Tutu Wells Site was prepared by CDM to evaluate the
public health and environmental risks associated with constituents in the soil and groundwater.
Both current and future risks associated with potential exposure to soil and groundwater from the
Tutu Wells Site were addressed in this risk assessment (CDM Federal Programs Corporation
1995a).
Based on the risk assessment, only the surface soil at Tillett Gardens was found to exceed
both the carcinogenic and non-carcinogenic acceptable risks. Groundwater risks were viewed for a
site-wide rather than property-specific perspective, and specific compounds were found to exceed
both the carcinogenic and non-carcinogenic risks for ingestion of groundwater. Subsurface soil did
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not exceed unacceptable risks for either carcinogenic or non-carcinogenic risks, where the soil is
undisturbed.
As indicated in Table 2-2, the site-specific carcinogenic risk determined by the USEP A was
exceeded for ingestion of surface soil at Tillett Gardens. The risk is attributed primarily to Aroclor
1242 (a PCB) and arsenic.
No properties other than Tillett Gardens had a carcinogenic risk from exposure to surface
soil, and all properties at the Tutu Wells Site were below the carcinogenic risk for exposure to
subsurface soil. The carcinogenic risk from ingestion of groundwater was exceeded for adults. The
constituents contributing the majority of the risk were PCE and vinyl chloride.
For non-carcinogenic risks, the hazard index (HI) was exceeded for children via ingestion
of surface soil at the Tillett property only; arsenic and manganese contributed to the majority of the
risk (Table 2-3). In addition, due to manganese, the HI was greater than 1 via the inhalation
pathway.
The HI was exceeded for all receptor populations including adult residents, children, site
workers, and future construction workers (Table 2-3). In each instance, manganese accounted for
the largest risk and was the only constituent of risk for site and construction workers. Total DCE,
PCE, antimony, and vanadium were above the hazard quotient (HQ) for ingestion of groundwater
by children.
Potential exposure pathways do exist for environmental receptors. Individual animals, such
as lizards, may be exposed to low to moderate risks. However, the risk assessment has determined
that the potential exposures to individual animals that may encounter COCs on-site will not result
in an unacceptable risk to animal populations (CDM Federal Programs Corporation 1995a).
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3. REMEDIAL ACTION GOALS AND GENERAL RESPONSE ACTIONS
This section presents the remedial objectives, goals, and general response actions identified
for the Tutu Wells Site. 
Remedial objectives and goals were established to address any
unacceptable risks identified in the USEPA Baseline Risk Assessment (CDM Federal Programs
Corporation 1995a). The USEPA's comments, made during the preparation of the RI Report
(Geraghty & Miller, Inc. 1995) and the final Baseline Risk Assessment (CDM Federal Programs
Corporation 1995a), were considered in the formulation of these goals and objectives.
3.1 
REMEDIAL ACTION OBJECTIVES AND PRELIMINARY REMEDIAL
GOALS
This section discusses the Remedial Action Objectives (RAOs) and preliminary remedial
goals (PRGs) that will form the basis for the remediation of the Tutu Wells Site. RAOs are broad,
media-specific objectives for protecting human health and the environment. These objectives were
derived from the National Contingency Plan (NCP), USEPA guidance, and the results of the RI.
PRGs are numerical standards and remedial endpoints for specific environmental media that, once
they have been achieved, ensure that the RAOs have been satisfied.
3.1.1 Remedial Action Objectives
The RAOs for human health protection at the Tutu Wells Site are as follows:
• 
Remove and/or control the sources of groundwater contamination.
• 
Remove contamination in groundwater to the extent practical.
• 
Control the migration of impacted groundwater and limit the downgradient (i.e.,
southerly) migration.
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• 
Prevent human ingestion of groundwater containing VOCs or BNAs in excess of
federal 
maximum contaminant levels (MCLs) and non-zero Maximum
Contaminant Level Goals (MCLGs) (see Table 3-1).
• 
Prevent human ingestion of groundwater containing site-related constituents in
excess of the USVIDPNR Standards for Groundwater.
• 
Prevent human ingestion of groundwater exhibiting excess lifetime cancer risks
greater than the range of 10"4 to 10"* or hazard (non-cancer) indices greater than
unity (1.0).
• 
Prevent human direct contact and exposure to contaminated soil that pose excess
lifetime cancer risks greater than the range of 10"4 to 10"6 or hazard indices greater
than unity (1.0).
• 
Minimize any potentially significant leaching of COCs from site soil into the
groundwater.
• 
Protect human health and the environment by minimizing upconing of highly
mineralized water and preventing saltwater intrusion. The bedrock aquifer in the
Tutu Wells Site has a finite safe yield based on the rate of groundwater recharge
from precipitation. Any groundwater remedial alternatives selected will have to be
designed so as not to withdraw groundwater in excess of the aquifer's safe yield.
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3.1.2 Preliminary Remedial Goals
PRGs consist of numerical limits or remedial target concentrations for specific constituents
in specific media. These goals can be derived from the applicable or relevant and appropriate
requirements (ARARs) identified for the site, naturally occurring or background concentrations, or
health-based calculations derived using USEPA guidance on the development of risk-based PRGs
(USEPA 1991b).
3.1.2.1 ARARs
Remedial actions must attain a general standard of cleanup that ensures protection of
human health and the environment, is cost-effective, and uses permanent solutions and alternative
treatment technologies or resource recovery technologies to the maximum extent practical.
Cleanup standards and remedial design guidelines are usually based on ARARs. The potential
ARARs for the Tutu Wells Site are divided into the following three major categories: chemical-
specific requirements, location-specific requirements, and action-specific requirements. These
ARARs are provided for federal and USVI statutes in Tables 3-2 to 3-7.
• 
Chemical-specific ARARs are health-based or risk-based numerical values or
methodologies which, when applied to site-specific conditions, result in the
establishment of numerical values that delineate the acceptable amount or
concentration of a chemical that may be found in, or discharged to, the ambient
environment.
• 
Location-specific ARARs are restrictions that may be placed on the concentration
of hazardous substances or the conduct of activities solely because they occur in a
particular location.
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• 
Action-specific ARARs are generally performance, design, or other similar
operational controls or restrictions on action related to management of hazardous
substances or pollutants. These requirements address the particular activities that
are selected to accomplish a remedy.
3.1.2.2 To-Be-Considered Material
TBC materials are non-promulgated advisories or guidance issued by federal or state
agencies. They are not legally binding, and do not have the status of potential ARARs, but
were considered in the selecting and implementing of remedial activities for the Site. For the
purposes of this FS, one criterion is classified as a TBC, the USEPA's Vadose Zone Model for
Soil Cleanup Concentrations (CDM Federal Programs Corporation 1995b). 
This TBC
proposes guidance levels to evaluate potential impacts to groundwater quality from
constituents in soil. These guidance levels are used in the FS as SSLs to determine if remedial
action is necessary.
3.1.2.3 Remedial Action Levels and Cleanup Goals
Other PRGs will include the potential remedial action levels (RALs) and cleanup goals
(CGs). RALs and CGs are developed to comply with ARARs and to be protective of human health
and the environment. The RALs are chemical-specific criteria or concentrations that are used to
determine if remediation is warranted. RALs can become CGs during the FS process if considered
appropriate. CGs are chemical-specific criteria or concentrations that determine the degree of
treatment or management required.
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RALs do not exist for soil. The USEPA Baseline Risk Assessment determined that the
COC concentrations detected in soil represent no risk via direct contact with human receptors, with
the possible exception of PCBs and manganese at the Tillett property. The only possible impact
from COCs in soil, therefore, is the potential for leaching to groundwater. For the Tutu Wells Site,
the USEPA has developed SSLs to be used as screening levels, to identity COC concentrations in
soil that could, by leaching, raise COC concentrations in groundwater above MCLs, and that may
therefore warrant remediation (CDM Federal Programs Corporation 1995b). A comparison of
compounds/analytes detected above the screening levels for soil is provided in Table 2-4.
For the purposes of this FS Report, RALs for groundwater are the MCLs established by
the USEPA for drinking water (see Table 3-1). The CGs for groundwater used in this report are
based on the anticipated discharge standards that apply to the location to which treated
groundwater is discharged (i.e., potable water, surface water, groundwater, or publicly owned
treatment works [POTW]) or on the groundwater quality standards if groundwater is treated or
controlled in situ. In cases where DNAPL potentially exists in the bedrock (e.g., near the
Curriculum Center and possibly near the OHenry Dry Cleaners), groundwater technologies are
discussed based on the ability of the technology to control further contamination by DNAPL, but
not to reduce or eliminate DNAPL concentrations. Where DNAPL exists, CGs based on the
groundwater source quality standards may not be achievable. 
A comparison of
compounds/analytes detected above RALs for groundwater is provided in Table 3-8.
3.2 IDENTIFICATION OF GENERAL RESPONSE ACTIONS
General response actions consist of broadly conceived actions or categories of activities
that will satisfy the RAOs for the Tutu Wells Site, either singly or in combination. General
response actions potentially capable of, and appropriate for, meeting the RAOs discussed above
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were first identified during planning activities for the RI (Geraghty & Miller, Inc. 1995). The
following medium-specific general response actions were retained for the Tutu Wells Site:
Soil
• No action
• 
Institutional controls
• 
Containment
• Treatment
• 
Removal and disposal
Groundwater
• No action
• 
Institutional controls
• Collection/containment
• 
Treatment
• Discharge
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4. IDENTIFICATION AND SCREENING OF REMEDIAL TECHNOLOGIES
Potential remedial technologies capable of fulfilling the general response actions and
meeting the RAOs set forth in Section 3.0 (Remedial Action Goals and General Response Actions)
have been identified and are evaluated in this section. Remedial technologies applicable to soil and
groundwater have been identified and screened for effectiveness and implementability.
The technologies evaluated in the following sections can, under appropriate conditions, be
protective of human health and the environment, attain ARARs and PRGs, and may be
implementable at the Tutu Wells Site. The technologies retained by the screening process are
further evaluated in Section 4.6 (Further Evaluation of Screened Technologies).
4.1 TECHNOLOGY IDENTIFICATION
The identification of potential remedial technologies for this report utilized several sources
of information, including the following:
• 
The remedial technologies contained in the USEPA "Guidance for Conducting
Remedial Investigations and Feasibility Studies Under CERCLA" (USEPA 1988a).
• 
The remedial technologies contained in the USEPA "Guidance on Remedial Actions
for Contaminated Groundwater at Superfund Sites" (USEPA 1988b).
• 
Technology evaluation reports and compendia published by the USEPA under the
Superfund Innovative Technology Evaluation (SITE) program.
• 
The remedial technologies contained in the USEPA "Presumptive Remedies: Site
Characterization and Technology Selection for CERCLA Sites with Volatile Organic
Compounds in Soils" (USEPA 1993).
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4.2 TECHNOLOGY SCREENING CRITERIA
As required by USEPA guidance (USEPA 1988a), the technologies identified for the
environmental media of concern were initially screened for effectiveness, implementability, and cost
criteria. The evaluation of the technology focused on the following considerations:
• 
The estimated areas or volumes of media to be remediated and meeting the goals and
objectives set forth in Section 3.0 (Remedial Action Goals and General Response
Actions).
• 
The implementability and the potential impacts to human health and the environment
during construction.
• 
The efficiency and reliability of the remedial technology or process option with respect
to the contaminants and conditions at the Tutu Wells Site.
Implementability is based on the technical and administrative feasibility of implementing the
technology. Technical implementability is used as an initial screen to eliminate those technologies
that are clearly ineffective and unworkable at the Tutu Wells Site. Administrative implementability
considers the ability to obtain necessary permits for on-site and off-site actions; the availability and
capacity of treatment, storage, and disposal services; and the availability of necessary equipment
and workers to implement the technology. 
Another factor that may affect administrative
implementability is the ability of USEPA and the DPNR to execute enforceable agreements with
responsible parties to better control withdrawal of groundwater. Unauthorized use of groundwater
from the Tutu aquifer must be minimized to enable the chosen remedial action to be implemented,
controlled, and effective.
Cost criteria play a limited role in initial screening of remedial technologies and process
options. Relative capital and operation and maintenance (O&M) costs are used in this section, and
more detailed cost analysis will be provided in Section 5.0 (Development and Screening of
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Remedial Alternatives). In accordance with USEPA guidance (USEPA 1988a), the relative costs
of technologies evaluated in this FS Report are characterized as low, moderate, or high (e.g.,
expensive) for comparison of similar technologies that would be utilized for the same objective.
Remedial technologies for soil are based on the guidance provided by the USEPA for
presumptive remedies (USEPA 1993). Review of this guidance indicates that, in order of
preference, soil vapor extraction (SVE), thermal desorption, and incineration are presumptive
remedies that can successfully address the type of soil contamination present at the Tutu Wells Site.
Due to the complex and heterogeneous soil characteristics at the site, application of these
technologies will be considered both in-situ and ex-situ. Because the screening and comparative
analysis of alternatives for soil are formulated in the USEPA (1993) guidance document, screening
of remedial technologies for soil is not required. However, further evaluations of additional
alternative technologies are provided for completeness.
4.3 
IDENTIFICATION AND SCREENING OF REMEDIAL TECHNOLOGIES
FOR SOIL
In this section, potentially applicable technologies for remediating the COCs in impacted
soil at the Tutu Wells Site are described and reviewed for technical implementability. A summary
of the screening results for soil is presented in Table 4-1.
4.3.1 
No Action
No action is defined as the absence of any protective steps to address the affected medium,
with the possible exception of periodic site monitoring. Consideration of no action is required by
the NCP because it evaluates the potential impacts associated with not implementing any remedial
action for soil. The results of the Baseline Risk Assessment (CDM Federal Programs Corporation
1995b) indicate that the no action alternative may be applicable to impacted soil at several of the
individual properties in the Tutu Wells Site area.
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No action will be retained for further consideration and used as a baseline for comparing
the effectiveness of active remedial measures for soil at the Tutu Wells Site.
4.3.2 Institutional Controls
Institutional controls encompass several strategies that limit or prevent the likelihood of
human and environmental contact with impacted soil. Although institutional controls can be
implemented to limit access to specific areas, they do not increase the volume or minimize
constituent concentrations in the affected environmental media. At sites where a potential exists
for exposure to impacted soil or groundwater, institutional controls can reduce the potential for
exposure.
One type of institutional control that can be implemented at the Tutu Wells Site is access
restrictions. Access restrictions are a type of institutional control that can be employed to address
soil and groundwater contamination problems. Access restrictions consist of preventing human
contact with contaminated soil. One such access restriction is a deed restriction.
Deed restrictions involve annotating the deed for the property to limit or prohibit use of the
property for specific purposes or for specific uses of the property and/or soil. For example, deed
restrictions could prohibit use of the property for residences, schools, or parks to prevent direct
contact with impacted soil. Similarly, deed restrictions could prohibit a wide range of potential soil
uses, such as use for fill at other properties.
Deed restrictions are a proven, reliable, and established method of institutional site control.
Minimal maintenance is required, and health risks associated with implementation of this remedial
technology are minimal. Costs associated with deed restrictions would include filing and legal fees
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and are anticipated to be moderate. Implementation and enforcement of deed restrictions would
require continual monitoring at the restricted properties to ensure compliance with the restrictions.
Deed restrictions will be retained for further consideration as a remedial measure for soil at
the Tutu Wells Site due to their potential effectiveness and implementability.
4.3.3 Containment
A containment technology considered for the contaminated soil at the Tutu Wells Site is
capping. Containment serves three functions. First, it prevents direct contact by humans with
impacted soil, thereby eliminating exposure pathways involving dermal contact, ingestion, or
inhalation. Second, it eliminates the possibility of erosion and transport of impacted soil. Third, it
reduces the infiltration of precipitation through the soil and the leaching of site constituents into the
underlying groundwater.
Containment of impacted soil can be attained by capping the soil in place to reduce the
potential for human exposure and control fugitive emissions from impacted soil. Caps can also be
low-permeability barriers placed over an area of soil contamination to prevent surface-water
infiltration (if potential leaching to groundwater is a concern). The types of materials that could be
used for caps include soil, clay, asphalt, concrete, and polymer membranes. With the exception of
concrete and asphalt, capping materials are generally covered by soil and vegetation compatible
with the region.
Due to the fact that much of the Tutu Wells Site is currently covered with asphalt and
concrete, at many properties, capping may consist only of checking the integrity of these surfaces
and repairing or expanding them where necessary. Many of the source areas at the Tutu Wells Site
are already capped by existing pavement, building foundations, or concrete pads. Improvement of
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existing surfaces and installation of new caps would eliminate direct contact and reduce or
eliminate leaching of contaminants to the underlying groundwater.
No disposal or transportation requirements for waste are associated with this remedial
technology. Only inspection and periodic maintenance costs are included to ensure the caps are
intact.
The capital costs associated with capping are dependent on the construction materials
selected for the cap and can range from low to moderate. The O&M costs will vary depending on
the type of capping system installed.
Containing the soil at the Tutu Wells Site by capping is technically implementable and will
be retained for further evaluation.
4.3.4 Treatment
As previously noted, the USEPA (1993) presumptive remedy guidance for treatment
technologies for VOC-impacted soil has identified SVE as the primary presumptive remedy. For
completeness, thermal desorption and incineration, which are secondary treatment options
identified in the USEPA (1993) guidance, are also evaluated in the preliminary screening of
technologies. Additional consideration is also given to bioventing, as it may be adaptable at
specific properties within the Tutu Wells Site and the application of similar technologies in an ex-
situ remedy. 
Ex-situ remedies are considered and evaluated in Section 4.3.5 (Removal
Technologies).
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4.3.4.1 In-Situ Soil Vapor Extraction
In-situ SVE is a treatment technology that consists of installing a network of vadose zone
extraction wells or trenches through areas where soil contamination with VOCs exists. VOCs
present in the unsaturated, interstitial spaces between the soil particles are extracted under the
influence of a vacuum that is induced by a blower. This action upsets the equilibrium that exists
between the constituents present in the interstitial vapor space and any constituents that might be
present in an adsorbed phase on the soil particles or be present in a free phase. As the constituents
in the vapor phase are removed by the vacuum, some of the adsorbed or free-phase constituents
adjust to the shift in equilibrium by volatilizing into the soil pore spaces. These newly volatilized
constituents are then removed under the constant influence of the vacuum that is induced by the
extraction blower. For biodegradable compounds, such as BTEX, added benefit is gained from the
enhanced biodegradation of these compounds by indigenous soil biota due to increased soil oxygen
levels.
Often, soil vapors extracted using this approach must be treated to reduce or destroy the
constituents present in the blower exhaust to acceptable discharge levels. Potential technologies
evaluated for treating the exhaust from the extraction blower include vapor phase granular
activated carbon (VPGAC), incineration, thermal oxidation (thermox), or catalytic oxidation (cat-
ox).
Based on published information (Mobil 1992) regarding the treatment of VOCs in air, the
following generalizations can be used as a guide to quickly determine an appropriate off-gas
treatment technology for an SVE system:
• 
VPGAC is generally used where total VOC concentrations are below 50 parts per
million by volume (ppmv) and where poorly adsorbed compounds such as vinyl
chloride do not require treatment. If air flow rates are low, VPGAC could prove to be
a cost effective method of air treatment despite high VOC concentrations.
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Use of a thermox unit is suggested to treat hydrocarbon off-gas containing chlorinated
VOCs present at concentrations greater than the 100 pprrv or 10 percent of the total
VOC concentration.
Use of a cat-ox unit is suggested to treat hydrocarbon off-gases when initial
concentrations are between 50 ppmv and 10,000 ppnv of total VOCs.
At most sites, SVE and bioventing system VOC off-gas concentrations will decline
rapidly (exponentially) with time. Based on industry experience, thermox or cat-ox
units can be removed from a property after 6 to 12 months of operation. Thus, at
certain properties, several off-gas treatment technologies could be used, depending on
the off-gas concentrations. Therefore, the off-gas control technology selection will be
a compromise between a unit that would provide adequate treatment at the higher
initial concentrations and one that would be adequate and cost-effective at the longer-
term, lower concentrations.
In applications that require thermox or cat-ox systems due to high VOC
concentrations, the off-gas treatment may be modified after the initial concentrations of
VOCs fall below 50 ppmv. A more cost-effective technology such as VPGAC is often
applied in the lower concentration range. If vinyl chloride is present in the off-gas, the
discharge concentration must be evaluated using air dispersion calculations to
determine if vinyl chloride vapor concentrations would create potential human health
concerns. Continued use of a thermox system may be required.
Due to the higher costs of the thermox and cat-ox units (between $60,000 and
$100,000 for a 600 standard cubic feet per minute [scfin] system), thermal destruction
equipment can be moved from one site to another for re-use to reduce capital costs and
maximize the use of the equipment.
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For the cost estimates established in this FS, it has been assumed that a therm-ox unit will
be used to treat vented VOC-laden air streams. Thermox was selected because chlorinated VOCs
can deactivate or degrade conventional catalysts and VPGAC is generally not cost effective at
recovering chlorinated VOCs at concentrations above 100 ppnv The Source Control Plan (SCP)
for Texaco has included a cat-ox unit for off-gas treatment. A general summary of off-gas
treatment technologies is provided in Table 4-2.
At the Tutu Wells Site, air dispersion modeling may be used to determine the need for off-
gas treatments. However, due to the low soil concentrations detected, no off-gas treatment is
anticipated for most of the individual sites. Furthermore, off-gas treatment, if any, should be of low
duration due to the exponential decay of the concentrations over time from the SVE or bioventing
systems.
SVE is a very reliable and cost-effective method for treating certain soil contaminated with
a wide range of VOCs, provided that the soil properties are conducive to this technology.
Implementability of the technology is moderate as permits for air discharge would be required.
Based on the cleanup standards for soil, SVE can be evaluated on a site-specific basis.
The capital costs for in-situ vapor extraction would be moderate to high, and O&M costs
would be moderate to high depending on the need and type of emission controls. The type of
emission controls required at each property would have to be further evaluated during the pre-
design phase. SVE will be retained for further consideration.
4.3.4.2 In-Situ Bioventing
In-situ bioventing is a treatment technology that is similar to SVE. The primary difference
between the two treatment technologies is that bioventing employs much lower air flow rates,
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thereby enhancing biodegradation and minimizing contaminant volatilization and extraction.
Drawing air through soil at low flow rates provides oxygen to indigenous bacteria and enhances
their ability to aerobically biodegrade COCs. By reducing air flow rates, the removal of moisture
from the vadose zone is minimized. Soil moisture is a factor that affects bacterial activity. A
bioventing system may include the reinjection of contaminated gases (with or without some
treatment), resulting in no off-gas discharge to the atmosphere, thus eliminating the need for vapor-
phase treatment and an air discharge permit. Supplemental oxygen can be added to the reinjected
gases to accelerate the rate of bioremediation.
Bioventing is particularly suitable at sites where non-halogenated volatile and semivolatile
organic compounds (SVOCs) and certain fuel hydrocarbons are the primary COCs. Bioventing of
halogenated VOCs may require additional precautions and in general is not very effective unless
there is a co-metabolite present. Application of this technology would require evaluation on a
property specific basis.
This treatment technology is relatively inexpensive to implement, as it does not require the
use of expensive equipment or intensive O&M; however, it could have some limitations at
properties where chlorinated VOCs are present. It is also very reliable and requires minimal
downtime for maintenance and repairs. This treatment technology will be retained for further
consideration.
4.3.5 Removal Technologies
Source removal can be achieved by excavating contaminated soil at the Tutu Wells Site.
The excavated material would be containerized and tested for waste classification. If the soils is
deemed non-hazardous, they could be disposed locally. If deemed hazardous, they would either be
treated ex-situ and disposed of on-site as backfill or transported off-site to a hazardous waste
treatment or disposal facility.
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The impacted soil can be removed from the Tutu Wells Site by mechanical excavation.
Standard excavating equipment, including backhoes, power shovels, and clamshells, can be used to
excavate soil and can be decontaminated afterward. The excavated material can be staged for
subsequent treatment or containment on-site or containerized and loaded directly into trucks for
off-site treatment or disposal. Exposure to impacted soil during removal can be addressed by
personal protective equipment. There is the potential for residential exposure to fugitive emissions
or dust during excavation. However, engineering controls can minimize emissions.
Several ex-situ treatment and disposal options related to removal technologies are further
discussed in this section. The technologies evaluated are Biopiles/ex-situ SVE, thermal desorption,
and incineration (USEPA 1993). Implementation of this technology is favorable assuming an
approved method of disposal is readily available, and/or replacement of treated soil can be
accomplished. Excavation and disposal is potentially applicable and this process option will be
retained for further analysis.
4.3.5.1 Biopiles/Ex-Situ SVE
Biopiles involve the ex-situ biological treatment of contaminated soil whereby the
degradation of organic contaminants by micro-organisms occurs in an aboveground, controlled
environment. Micro-organisms may be either indigenous or externally introduced. Oxygen is
supplied to the piles via ambient air injection. The air can be blown directly into the pile or drawn
through the piles using a vapor extraction blower. Where compounds are readily volatilized, such
as is the case with many chlorinated VOCs, the bulk of the soil treatment takes place by
volatilization with little or no biodegradation of the VOCs taking place. Biopiles applied to soil
contaminated with BTEX, petroleum compounds, and other readily biodegradable hydrocarbons
are designed to allow more biodegradation to take place with little or no volatilization.
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An ex-situ SVE system is configured similar to a biopile but is designed to optimize
volatilization. These systems are designed to draw a vacuum in a covered pile, thus inducing air
flow through the soil piles and volatilizing the VOCs. Ex-situ SVE systems are applied in
situations where in-situ SVE is impractical or of limited use. Chlorinated VOCs, BTEX, and other
VOCs can be treated with this technology.
Depending on air emission limits, control of the VOC emissions from the biopile may be
required. Vapor treatment will be dependent on contaminants; the same technologies evaluated for
in-situ SVE treatment would apply.
The capital costs associated with biopiles and ex-situ SVE would be moderate to high due
to the excavation of soil and the off-gas treatment technology used (if necessary). O&M would be
moderate to high and would be based on the off-gas treatment technology used. 
These
technologies will be retained for further evaluation.
4.3.5.2 On-Site Thermal Desorption
Thermal desorption is a thermal treatment technology that involves the application of
elevated temperatures to soil to volatilize VOCs from excavated soils. 
Application of this
technology may require the collection and treatment of the off-gases that are produced. The
temperature used for thermal desorption (typically from around 400 to 1,100 degrees Fahrenheit
[°F]) depends on the volatility and boiling point of the COCs.
Thermal desorption has been shown to be effective in treating soil with VOCs. Commercial
units exist and are in operation, but use of these facilities would require off-island transport and
disposal of excavated soil. On-sSte thermal desorption units are usually expensive and are cost-
prohibitive where soil volumes are small.
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The capital costs for thermal desorption would be high and O&M costs would be moderate
to high depending on the need and type of emission controls. The costs to excavate and stockpile
the contaminated soil would be moderate to high depending on the volume, area to be excavated,
and COCs present. More cost-effective technologies are under consideration; this technology is
not retained for further analysis.
4.3.5.3 Incineration
Incineration is another treatment technology similar to thermal desorption except that
incineration treats VOCs in the excavated soil to temperatures greater than 1,000 °F in the presence
of oxygen. This causes volatilization and combustion of the VOCs, converting them to carbon
dioxide (CCh), water, hydrogen chloride (HC1), nitrogen oxides (NOX), and sulfur oxides (SOX).
Implementation of on-site incineration would be difficult due to permitting requirements and
limited spacing which allows for air dispersion of emissions prior to reaching potential receptors.
The disposal of incinerated ash, which would likely be considered a hazardous waste due to the
potential metals content, would present implementation difficulties because off-island disposal
would be required.
The most well-developed, proven, and commercially available form of thermal destruction
is rotary kiln incinerators. These incinerators consist of slightly inclined, refractory-lined cylinders
where soil and auxiliary fuel are injected into the high end of the kiln and passed through the
combustion zone as the kiln slowly rotates for incineration. Temperatures within the combustion
zone typically range from 1,200 to 1,800 °F, and the retention time can vary from several minutes
to 1 hour or more. VOCs are oxidized to gases and inert ash within this zone, with ash being
removed at the lower end of the kiln. Flue gases are passed through a secondary combustion
chamber and then through air pollution control units for paniculate and acid gas removal. Off-site
disposal of soil would be required as the soil would not be reusable for fill or replacement.
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The capital and O&M costs for this technology are high. The costs associated with
excavating and stockpiling the contaminated soil are moderate to high depending on the volumes
and depths of impacted soil. This technology is not retained for further consideration as there are
more cost-effective and implementable technologies under consideration.
4.4 
IDENTIFICATION AND SCREENING OF REMEDIAL TECHNOLOGIES
FOR GROUNDWATER
In this section, potentially applicable technologies for remediating the VOC contamination
in groundwater at the Tutu Wells Site are described and evaluated. If treated water is considered
for potable use, additional technologies to treat naturally occurring inorganic contaminants (e.g.,
precipitation, reverse osmosis, and ion exchange) are also evaluated. The primary COCs include
chlorinated VOCs and petroleum-related hydrocarbon compounds.
During this screening process, technology types or technology process options are
eliminated from further consideration based on effectiveness, implementability, and/or cost. The
following sections present the results of this technology screening for the technologies evaluated. A
summary of the screening results for groundwater is presented in Table 4-3.
4.4.1 No Action
No action is a general response action that is required by the USEPA and the NCP to be
carried through to the detailed analysis phase of the FS. The no-action approach will be considered
for evaluation of the potential impacts associated with not implementing any remedial action for
groundwater. No action will be retained for further consideration and used as a baseline for
comparing the effectiveness of active remedial measures for groundwater underlying the Tutu
Wells Site.
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4.4.2 Institutional Controls
Institutional controls encompass several strategies that limit or prevent the likelihood of
human and environmental contact with impacted soil or groundwater. Although institutional
controls can be implemented to limit access to specific areas, they do not increase the volume or
minimize constituent concentrations in the affected environmental media. 
At sites where a
potential exists for exposure to impacted soil or groundwater, institutional controls can effectively
reduce the potential for exposure to site-related constituents.
4.4.2.1 Access Restrictions
One type of institutional control that can be implemented at the Tutu Wells Site is access
restrictions. Access restrictions are a type of institutional control that can be employed to address
soil. Access restrictions consist of preventing human contact with impacted groundwater. One
such access restriction is deed restrictions.
Deed restrictions involve annotating the deed for the property to limit or prohibit use of
groundwater on the property for specific purposes or for specific uses. For example, deed
restrictions could prohibit a wide range of potential groundwater uses, such as pumping for water-
supply use (development of the groundwater for human consumption), agricultural use (watering
livestock or irrigating crops), or industrial use (cooling water or process make-up water).
Deed restrictions are a proven, reliable, and established method of institutional site control.
No maintenance is required, and health risks associated with implementation of this remedial
technology are minimal. Costs associated with deed restrictions would include filing and legal fees
and are anticipated to be low. For those sites with contaminated groundwater, provisions for an
alternate water supply would have to be made.
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Deed restrictions will be retained for further consideration as a remedial measure for
groundwater at the Tutu Wells Site due to their potential effectiveness and implementability.
4.4.2.2 Alternate Water Supply
Alternative residential water supply options are often considered in emergency situations,
and/or when it is not practicable or feasible to actively restore groundwater to drinking water
quality, and access to impacted groundwater is restricted. Three options are available for providing
an alternate water supply source, including extension of public water supply lines, trucking water,
and installation of a new community well for water supply.
4.4.2.2.1 Public Water Supply Extension
This remedial technology involves providing a supply of drinking water from a suitable,
non-contaminated source to residents in the affected areas. This can be accomplished in the Tutu
Wells Site area by extending the existing municipal water supply system in the area (managed by
the Virgin Islands Water and Power Authority [WAPA]) to the affected users. Plans for future
upgrades exist and they could be expanded to include connections to properties that have impacted
residential wells.
The extension of the existing water supply system to affected users would be technically
feasible, but construction of waterline extensions would be very expensive due to the shallow depth
to bedrock and length of water line installation necessary to provide water to all affected
residences. Connection costs for residences near the existing water main would be lower
(approximately $2,000 per residence). Use of the public water supply system will not restore
former commercial water supply entities in the Tutu Wells Site.
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A public water supply extension for residential consumptive use will be retained for further
consideration as a remedial alternative for groundwater at the Tutu Wells Site.
4.4.2.2.2 Trucking Water
In 1987, the DPNR closed 13 commercial wells and five private wells in the Tutu Wells
Site area. Subsequently, the USEPA initiated a limited CERCLA Removal Action that included
the delivery of water by tank trucks to the residents affected by the closure of the wells. This water
delivery has been accepted by the USEPA as permanent solution for affected residents. It may be
an option for consideration on a permanent basis for all residents in the Tutu Wells Site. Costs
associated with trucking water would be high and would be contingent on the availability of water
in other places in St. Thomas.
Trucking of water has been accepted in the past as a remedial alternative for groundwater
supply at the Tutu Wells Site. For this reason, it will be retained for further consideration.
4.4.2.2.3 New Community Well
The installation of a new uncontaminated supply well for use in the affected Tutu Valley is
another alternate water supply option. This new supply well could be used as a community
watering point by the residents in the area who now rely on other sources of water (e.g., trucked
water).
A new supply well may be technically implementable, but the cost of locating and
developing and distributing water from an alternate supply well would be high. The well would
have to be located outside of the area of impacted groundwater, and pipelines or trucking to
distribute the water to residents would be required. There would also be no guarantees as to the
quantity or quality of water in a new location.
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This technology will not be retained for farther consideration as a remedial alternative for
the Tutu Wells Site, due to the high costs associated with locating an alternate water supply well
and providing the required distribution operations and piping or trucking.
4.4.3 Collection/Containment
Collection of groundwater refers to the process of extracting or otherwise collecting
impacted groundwater, and containment restricts migration of the impacted groundwater to other
areas. Collection can be accomplished using subsurface drains, extraction wells, and well points.
Containment can be accomplished by creating hydraulic barriers using extraction wells or through
vertical physical barriers such as slurry or cutoff walls.
4.4.3.1 Extraction
Groundwater extraction is a common and proven method of collecting impacted groundwater and
can be used effectively to hydraulically contain impacted groundwater from migrating beyond a site
perimeter. In this section, several methods of extraction are described and evaluated for use at the
Tutu Wells Site.
4.4.3.1.1 Extraction Wells
Groundwater extraction wells are a common method for intercepting impacted
groundwater. Extraction wells have been utilized extensively at other Superfund sites and can be
installed in most terrains.
The anisotropic conditions at the Tutu Wells Site would require additional testing to
develop and document an extraction well system that hydraulically contains the contaminated
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groundwater. Based on field measurement adjustments and monitoring, a groundwater extraction
well system could be installed that would contribute to the improvement of groundwater quality at
the Tutu Wells Site by reducing constituent migration and removing COCs from the groundwater.
If existing supply wells or monitoring wells are utilized for collection of impacted
groundwater, no capital costs for drilling would result. Otherwise, costs associated with drilling
would be incurred. Drilling new wells for extraction of groundwater may require more wells than
initially projected because some extraction wells may not provide the desired yield or capture zone.
Capital costs would be incurred for purchase and installation of the extraction pumps. These costs
would be relatively high due to the need for specialized construction materials (e.g., stainless steel,
Teflon, or other non-corrosive metals/polymers for wetted parts) to resist the corrosive effects of
chloride ions and other dissolved species present in the groundwater. O&M costs would be
relatively high due to the energy requirements and general upkeep and maintenance of the pumps
and well screens.
Extraction wells will be retained for further consideration. The decision to retain this
technology was based on the potential effectiveness in enhancing groundwater remediation under
the Tutu Wells Site.
4.4.3.1.2 Extraction/Injection Wells
This technology involves the reinjection of treated groundwater into the aquifer through
injection wells by pumping or gravity flow. Reinjection has been used at several sites throughout
the United States. The fundamental purpose of using injection wells is to ensure recharge of the
aquifer and at the same time enhance the groundwater remediation by increasing the hydraulic
gradient toward the extraction wells.
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Controlling flow in fractured bedrock may not be achievable because of the low
permeability and anisotropic nature of the aquifer. Plugging of bedrock fractures with precipitates
and biological growth will decrease injection well performance and increase O&M costs. Also,
there is a possibility of inducing lateral and/or downward migration of contaminants. Groundwater
modeling and/or additional field measurements would be required to determine the recharge and
recovery rates for the aquifer. A permit to discharge to groundwater would also be required and
would require a treatment facility that would have to meet stringent discharge standards (e.g.,
MCLs).
The capital costs would be moderate to high depending on the number of injection wells
required. The costs to operate and maintain the wells would be high.
This technology is not retained for further consideration because of the anticipated
limitations in controlling hydraulic containment during combined extraction and injection in an
anisotropic and complex aquifer.
4.4.3.2 Subsurface Drains
Subsurface drains consist of trenches excavated below the water table and filled with highly
permeable material, such as gravel, and perforated piping as collection media. The permeable
material and piping serve as conduits to induce flow from the subsurface to a collection point for
extraction and treatment. The subsurface drain serves as a continuous barrier that maximizes
groundwater extraction and minimizes contaminant migration. When gravity flow can be induced
through proper design and construction, subsurface drains can operate very cost-effectively.
The effectiveness of subsurface drains may be reduced by the occurrence of pervious
bedrock throughout the area. Should subsurface drains be constructed in areas of highly pervious
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bedrock, the drains may create enhanced migration pathways from the contaminant sources to
bedrock fractures currently free of contamination.
Subsurface drains are unsuitable for remediation of the groundwater underlying the Tutu
Wells Site due to the shallow depth to bedrock. The anisotropic conditions present in the area
would make it difficult to avoid creating migration pathways that may spread, rather than contain,
the contaminated groundwater. Furthermore, contaminated groundwater also occurs at a depth of
30 to more than 100 feet bis throughout the Tutu Wells Site. Subsurface drains could not be
installed at the Site because conventional excavation cannot reach the depth required to create an
effective hydraulic barrier. Even if specialized excavating equipment could be found to reach the
required depths, the construction costs in bedrock would be excessively high.
Subsurface drains will not be retained for further consideration because of the difficulties
associated with technical implementability and the excessive cost associated with construction.
4.4.3.3 Well Points
Well points are another common method of intercepting or collecting contaminated
groundwater. Well points are similar to groundwater extraction wells in many respects. The
primary differences are that well points are limited to smaller diameters and shallower depths and
are most commonly installed in unconsolidated deposits. Due to the small diameters of well points
(i.e., 2 inches or less), well points are interconnected (i.e., manifolded) to a central centrifugal or
suction-lift pump above land surface rather than using individual pumps in each well point. Because
of these limitations, well points are usually employed for temporary construction, such as
dewatering at construction sites with a relatively shallow water table.
Well points are not a suitable method of collecting groundwater underlying the Tutu Wells
Site. They would be ineffective because of the significant depth to groundwater (30 to 100 feet
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bis) and could not be constructed because of the prohibitive depths. Well points will not be
retained for further consideration because of their ineffectiveness and construction difficulties.
4.4.3.4 Vertical Barriers
Vertical barriers are a remedial technology group that encompasses slurry walls and
synthetic membrane cutoff walls. Both types of vertical barriers form physical barriers that restrict
or prevent the migration of contaminated groundwater to other areas that are clean or less
contaminated. These barriers can also be used in applications where clean groundwater from
upgradient areas can be directed around the contaminated areas.
4.4.3.4.1 Slurry Wall
Slurry walls are the most common type of vertical barriers to control groundwater
migration. A slurry wall is usually constructed of soil and bentonite as a means of reducing the
horizontal permeability of the soil. Slurry walls are generally extended 2 to 3 feet into a confining
geologic unit, and they are usually not installed through bedrock. Excavation of bedrock for slurry
wall installation is expensive due to the specialized equipment required to remove the rock.
A slurry wall is constructed by using a backhoe to excavate a 2.5- to 4-foot wide trench in
one pass. The trench is kept open by hydraulic shoring through the use of bentonite slurry. The
bentonite slurry creates a filter cake on the sides of the trench because the slurry flows laterally into
the soil. This filter cake consists of a layer of bentonite with low permeability. The trenches are
generally dug by using a small backhoe and are less than 40 feet deep. Greater trench depths can
be attained by using track-mounted backhoes and clamshell excavators attached to a kelly bar or
crane. The practical maximum depth limit for slurry walls is about 100 feet in unconsolidated
deposits.
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Typically, soil excavated from the trench is used as backfill material to mix with the
bentonite slurry. The permeability of the constructed slurry wall should be on the order of 10^ to
10'7 centimeters per second (cm/sec). To improve the overall effectiveness, slurry walls are often
constructed in conjunction with extraction wells and a cap.
Implementing the use of slurry walls at the Tutu Wells Site would be very difficult because
contaminated groundwater underlying the site occurs mostly in fractured bedrock. For a slurry
wall to function properly, it would need to be constructed through the bedrock and be keyed into
an underlying unit. Based on geologic information, a suitable confining unit has not been identified
at the Tutu Wells Site. Slurry walls are not generally excavated through bedrock due to the
specialized construction techniques (e.g., use of explosives) required. Importing fill material may
also be required as materials removed from the trench may not be satisfactory for slurry wall
construction. Specialized construction equipment in the Virgin Islands, if available, would be
expensive, and would be difficult to implement.
Slurry walls will not be retained for further consideration based on technical
implementability limitations and the presence of bedrock, which creates very high construction
costs.
4.4.3.4.2 Synthetic Membrane Cutoff Walls
Synthetic membrane cutoff walls are similar to slurry walls because they also involve the
excavation of a trench. After the trench is excavated, a synthetic membrane (typically a sheet of
polyethylene) is placed so that it covers the sides and bottom of the trench. Backfill material is then
placed and compacted to fill the trench void.
Synthetic membrane cutoff walls share the same technical implementability limitations that
make slurry walls unsuitable for the site. Synthetic membrane cutoff walls are generally limited to
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even shallower depths because no means of hydraulically shoring the sides of the trench exist to
prevent collapse. The use of a synthetic membrane cutoff wall also requires a significant amount of
material to fill the trench void, and fill material is expensive. Therefore, this technology is typically
implemented only when groundwater occurs within a few feet of the land surface. As with slurry
walls, synthetic membrane cutoff walls are generally not installed into bedrock.
This remedial technology will not be retained for further consideration. Similar to slurry
walls, the decision not to retain this technology was based on the problems with technical
implementability and the very high construction costs.
4.4.3.5 Enhanced Groundwater Recovery
Enhanced groundwater recovery is a remedial technology group that encompasses
technologies that help reduce the time required for remediation. The enhancement recovery
techniques evaluated are bedrock fracturing and vacuum enhanced recovery.
4.4.3.5.1 Bedrock Fracturing
Bedrock fracturing is a technology that is used to increase the flow of contaminated
groundwater to extraction wells. Fracturing can be performed through the application of high
pressure air or water to enhance existing fractures or create new fractures around the extraction
wells. Another option would consist of creating an artificial fracture zone through controlled
blasting to intercept contaminated groundwater flow. 
Fracturing would be positioned
perpendicular to the groundwater flow, and extraction wells would be installed within this fracture
zone.
The advantage of fracturing is the potential to increase the yield of extraction wells. By
increasing the yield, the extraction wells could be pumped at a higher rate and the time for
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remediation would be reduced. However, maximum extraction rates would be limited by the
established safe-yield of the aquifer within the Tutu Wells Site. Costs associated with using
explosives would be high and O&M costs would be moderate.
Potential blasting restrictions due to underground utilities, residential areas, and buildings
may limit the use of this technology at the Tutu Wells Site area. Another limitation is the possible
presence of DNAPL contamination in the bedrock. Fracturing could mobilize DNAPL and
enhance the downward and lateral migration of phase-separated contaminants.
Because this technology would be administratively difficult to implement and would have
technical limitations, bedrock fracturing is not implementable and will not be retained for further
consideration.
4.4.3.5.2 Vacuum Enhanced Recovery
This technology utilizes a vacuum to accelerate groundwater flow in low permeability
formations. Vacuum extraction wells are installed in the areas of concern, and a vacuum is applied
to the headspace above the static water level in these wells. Vapor and groundwater are extracted
simultaneously. The combined effect (liquid and vapor removal) may significantly increase the
contaminant removal rate.
The capital costs of vacuum enhanced recovery (VER) are moderate due to the
specialized construction of dual extraction wells. O&M costs would be dependent on the number
of dual extraction wells and blowers required. Implementation in bedrock would be difficult due to
the high potential for short-circuiting in bedrock. Extensive pilot testing would be required to
ensure its effectiveness.
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Due to limitations (i.e., short circuiting) of controlling VER in bedrock, and because other
more applicable technologies are under consideration, this technology is not retained for further
consideration.
4.4.4 
Treatment
This section presents two methods of treatment for groundwater (in-situ and ex-situ
treatment).
4.4.4.1 In-Situ Treatment
In-situ treatment of affected groundwater consists of those technologies that can be applied
without the extraction of groundwater. Potential in-situ remedial technologies include air sparging
and bio-sparging.
4.4.4.1.1 Air Sparging
Air sparging is an in-situ treatment technology that can be applied without the extraction of
groundwater to reduce organic concentrations in the subsurface environment. Air is injected below
the contaminated saturated zone, causing turbulence and groundwater mixing, which increases the
rate of soil and water contaminant desorption. Contaminants are transferred to the air phase and
the air is pulled through the vadose zone to ground surface by extraction or vacuum wells.
Air sparging is most applicable in relatively permeable and homogeneous geologic
formations. Its effectiveness is greatly diminished by the presence of clay layers or variations in
permeability. Heterogeneous soil or complex bedrock fracture patterns may force the injected au-
to travel in a horizontal direction and drive the contaminants into uncontaminated areas. The
anisotropy and relatively low permeability of the fractured rock and the depth to groundwater at
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the Tutu Wells Site limit the applicability of this technology. The capital cost of this option is
moderate and O&M would be low to moderate. Air sparging could be considered on a property-
specific basis at the Tutu Wells Site and will be retained for further consideration.
4.4.4.1.2 Bio-Sparging
Bio-sparging is an in-situ technology that can be used to remediate biodegradable organic
compounds in subsurface saturated zones. The technology consists of introducing small amounts
of air and nutrients into the subsurface to enhance the natural aerobic biodegradation of organic
contaminants.
As with air sparging, depending on the geologic and hydrogeologic conditions, this
technology can cause contaminants to migrate. The potential for contaminant migration limits the
applicability of bio-sparging at the Tutu Wells Site; however, it may be appropriate at specific
properties. Chlorinated VOCs in groundwater, which extend over a much larger area than the
petroleum-related compounds, are not effectively biodegradable under aerobic conditions.
The cost of this option is low and O&M requirements are minimal. This technology is
technically feasible; however, it would require additional evaluation to determine its effectiveness.
Bio-sparging will be retained for further consideration.
4.4.4.2 Ex-Situ Treatment
Ex-situ treatment involves groundwater extraction followed by some form of treatment and
discharge. The range of potential treatment technologies for VOCs in groundwater will be further
limited by the ARARs identified for the site.
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The ex-situ treatment technologies that will be considered for remediating the
groundwater at the Tutu Wells Site are air stripping (packed tower aeration); granular activated
carbon (GAC) adsorption; ultraviolet oxidation/reduction; and GAC fluidized bed systems for
organic constituent treatment. To treat naturally occurring inorganic constituents; filtration,
precipitation, flocculation, sedimentation, reverse osmosis, and ion exchange are being evaluated.
These technologies are considered highly reliable for the treatment of groundwater and are
screened in this section.
4.4.4.2.1 Air Stripping
Air stripping involves the transfer of VOCs from the liquid to the gaseous phase using a
countercurrent air/water scrubber. 
This process usually involves aeration of the extracted
groundwater in a packed tower. The tower packing consists of inert structured plates or randomly
dumped geometric shapes. Both types of packing provide large surface areas for contact between
the water and air phases.
Packed tower aeration is a proven technology that has been used to treat groundwater at
numerous groundwater remediation sites. Proper operation of the process has demonstrated high
levels of removal effectiveness for many VOCs. In some cases, complete treatment may require
pretreatment or polishing to remove other constituents in addition to the VOCs. Therefore, air
stripping may be a stand-alone technology for certain contaminants or may be one process in a
more complex treatment system. Depending on contaminant loadings and regulatory requirements,
treatment of the exhaust gases from the air stripper may be required to destroy or capture the
VOCs that are transferred into the air phase.
The most common form of off-gas treatment is typically VPGAC. However, thermox or
cat-ox units (as described in Section 4.3.4.1 [In-Situ Soil Vapor Extraction]) can be utilized where
total VOC vapor concentrations exceed 50 ppnv, or where chlorinated VOCs are present. Cat-ox
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is usually not considered where the concentrations of chlorinated VOCs are greater than 100 ppm,,,
as they can deactivate conventional catalysts. A summary of off-gas treatment technologies is
provided in Table 4-2.
Based on Geraghty & Miller's preliminary estimates for contaminant concentration in
groundwater, no off-gas treatment should be required for the pumping scenario(s) considered. The
need for off-gas treatment will be determined during the pre-design phase of the project.
Air stripping towers involve simple installation and start-up procedures. The system
pumps and blowers are easily maintained, and the equipment draws minimal power. However,
regular maintenance may be required to maintain optimal operating conditions. If properly
maintained, a long service life can be expected for air stripping equipment.
Capital costs for air stripping would be low to moderate. O&M costs would be moderate
to high depending on the need and type of emission controls, if required. Because it is very
effective for removing VOCs present in the groundwater underlying the site, air stripping will be
retained for further consideration. The decision to retain this technology for further consideration
was based on the potential effectiveness and implementability of air stripping.
4.4.4.2.2 Granular Activated Carbon Adsorption
Adsorption utilizes porous media to cleanse waste streams of impurities. Typically, GAC
is used because it has a higher affinity for many hydrocarbons and certain inorganic constituents.
The adsorption mechanism is hindered, however, by the presence of some inorganic compounds,
thus requiring removal of metals and/or solids prior to adsorption by GAC. Although adsorption
does not destroy contaminants, it facilitates their disposal by transferring them from a fluid phase to
a solid phase and concentrating them.
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GAC adsorption would be an effective means of removing most VOCs present in the
groundwater underlying the Tutu Wells Site. GAC adsorption does not effectively remove vinyl
chloride. One way to reduce the rate of GAC depletion is to couple this technology with air
stripping to remove the major portion of the VOCs. In such an application, GAC would serve as a
polishing system to remove the remaining VOCs in the water effluent from the air stripper to attain
the required system discharge limits.
GAC adsorption is also implementable given the site conditions. It is both constructable
and operable and poses only minimal risks to human health and the environment. Close monitoring
and periodic GAC replacement is necessary to prevent constituent breakthrough. Replacement is
generally accomplished by either regeneration or acquisition of virgin GAC and disposition of spent
GAC. Specialized equipment or labor is not required for GAC adsorption, and the necessary
equipment is commercially available.
Capital costs related to GAC adsorption are moderate to high depending on the size of the
contacting beds and on whether any ancillary equipment is needed. O&M costs would be
dominated by the costs for transportation and disposal or regeneration of the spent GAC.
Depending on the rate at which the GAC is exhausted, these costs would also be moderate to high.
Because it would be effective in the removal of VOCs present in the groundwater
underlying the site, GAC adsorption will be retained for further consideration.
4.4.4.2.3 Filtration
Filtration is a technology that utilizes porous media to remove suspended solids from a
waste stream by providing a preferential flow path for water while preventing the migration of
suspended particles in the water, based on particle size. Commonly used filter media are sand,
anthracite, or other specialty medias. Filtration is a proven and effective technology for the
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removal of suspended particles and is relatively easy to implement. 
However, periodic
backwashing to discharge trapped particles, which would require monitoring and maintenance,
would be required. Capital and O&M costs would be moderate. Filtration may be used as part of
a more complex treatment system. Due to its potential effectiveness, filtration will be retained for
further evaluation.
4.4.4.2.4 Precipitation, Flocculation, and Sedimentation
Precipitation, flocculation, and sedimentation have been applied widely to a variety of
wastewaters for the removal of suspended solids and metals. The groundwater enters a rapid mix
tank where chemicals are added to oxidize the suspended metals, soften the water, and adjust the
pH to preferentially precipitate the target metals. The water then flows to a chamber in which a
flocculent (e.g., anionic polymer, cationic polymer, and/or alum) is added and gently agitated so as
not to shear the floe. The water then flows to a settling basin in which the flocculated particles
/*•—\ 
agglomerate and settle quiescently. Sedimentation relies on gravity to remove flocculated particles
(as opposed to filtration, which screens particles of a given diameter).
Precipitation, flocculation, and sedimentation constitute a proven technology for the
removal of metals, insoluble inorganic salts, and suspended solids. This technology is dependent
on chemical additives and requires regular sludge removal and disposal; therefore, O&M costs
would be moderate. These processes will be retained for further consideration.
4.4.4.2.5 Reverse Osmosis
Reverse osmosis can be used for the separation of both organic and inorganic constituents
from an aqueous stream. 
Separation is achieved by preferential passage of one or more
constituents in an aqueous medium through a semi-permeable membrane. An applied pressure is
used to overcome osmotic pressure, which is a result of a solution trying to reach an equilibrium
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condition. Typically the operating conditions of these systems consume large amounts of energy to
establish the required pressure differential. Effluents from the process include a permeate stream,
composed primarily of water, and a concentrate stream containing water and the constituents
removed from the water. The concentrate stream may require treatment or disposal as a regulated
material.
Reverse osmosis has been demonstrated to be an effective remedial technology for the
treatment of dissolved nitrates and metals in groundwater. Organic compounds with a molecular
weight of greater than 200 are generally removed by this process. 
Pretreatment of the
groundwater is required if oil and grease and/or suspended solids are present in the water. The
technology is highly temperature-sensitive, not easily adaptable to variation in flow and loading,
complicated to operate and maintain, and very high in cost. This technology has been used in other
portions of the Tutu Valley for removal of dissolved solids and is potentially applicable at the Tutu
Wells Site. However, capital and O&M costs are high. This technology will be retained for further
consideration.
4.4.4.2.6 Ion Exchange
Ion exchange is a highly dependable technology for inorganic and some organic
compounds. It involves the transfer of constituent ions and cations from water to an exhaustible
ion exchange resin. This resin is relatively insoluble granular material that has acid or basic radicals
exposed on its surface. As ion exchange generally softens the water, a polishing step may also be
required to adjust effluent hardness. Ion exchange systems have low O&M costs but a high capital
cost. This option is a proven technology for the removal of inorganic compounds and is retained
for further analysis.
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4.4.4.2.7 Ultraviolet Oxidation/Reduction
Ultraviolet (UV) oxidation/reduction is a technology that destroys dissolved organic
constituents (e.g., VOCs) in groundwater by means of chemical oxidation. Specifically, the
oxidation process that takes place involves an oxidation-reduction (redox) reaction because one of
the species involved gains electrons and another loses electrons, thereby destroying organic
compounds. Ozone and hydrogen peroxide are widely used as oxidants in conjunction with UV
light to remove organic compounds. Due to the expense, safety issues, and instability of ozone,
hydrogen peroxide, rather than ozone, will be considered for the Tutu Wells Site.
UV light catalyzes the chemical oxidation of organic compounds in groundwater by its
combined effect on the organic constituents and its reaction with hydrogen peroxide. Many
organic constituents absorb UV light and undergo a change in their chemical structure, and many
become more reactive with chemical oxidants. UV light at less than a 400-nanometer (nm)
wavelength reacts with hydrogen peroxide molecules to form hydroxyl radicals. 
UV
oxidation/reduction has been demonstrated to completely destroy chlorinated VOCs such as those
found in the Tutu Wells Site (e.g., PCE, and TCE) with minimal air emissions.
A UV oxidation/reduction system can handle variable flow rates and loadings; however,
where groundwater is excessively hard, pretreatment for the removal of dissolved solids is
required. Without pretreatment, the calcium deposits would coat the quartz tubes and prevent the
extracted groundwater from being exposed to UV light.
The capital and operating costs are high, and the O&M costs are high due to the
complexity of the system and energy consumption. Although this technology has high associated
capital and O&M costs, it is an effective treatment technology for the COCs found in groundwater
in the Tutu Wells Site. This technology will be retained for further consideration.
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4.4.4.2.8 GAC Fluidized Bed System
The GAC fluidized bed system is a bioremediation technology that combines the use of
activated carbon with an aerobic or anaerobic biological process to treat biologically degradable
VOCs in groundwater. Activated carbon is utilized as the inert medium for attached microbial
growth in the fluid bed reactor. As water passes upward through the bed of medium, the bed lifts
and expands until it "fluidizes." This increases the surface area available for microbial growth,
which enables an increased rate of organic compound degradation. The increased surface area
offers the advantage of reduced system size, making the GAC fluid bed system easily portable. As
the microorganisms begin to grow, a bio-film develops, grows, and rises to the top of the bed
where the film is removed. Little, if any, off-gas is produced, and a minimal amount of carbon
replacement is necessary since the carbon is biologically regenerated within the fluid bed.
GAC fluidized bed reactors would be particularly effective in treatment of biodegradable
petroleum-related COCs identified in the Tutu Wells Site groundwater. Capital and O&M costs
would be moderate. This technology is considered to be potentially applicable to the Tutu Wells
Site and therefore will be subject to further analysis.
4.4.4.3 Natural Remediation
Natural remediation is the reduction of constituent concentrations through attenuation and
degradation. Natural attenuation relies on the natural ability of groundwater to lower contaminant
concentrations through physical, chemical, and biological processes until cleanup levels are met.
Portions of the Tutu Wells Site aquifer that have been impacted by site constituents will naturally
attenuate with time. Active remediation of these areas through extraction and treatment will not
enhance or shorten the time frame in which aquifer remediation can occur. Monitoring and
institutional controls would also be implemented to ensure that no off-site receptors will be
impacted. Capital costs and O&M costs would be low to moderate. As this technology has
potential use at the Tutu Wells Site, this technology will be retained for further consideration.
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4.4.5 Discharge
The discharge point of treated groundwater will be an important factor that will affect the
cost and implementability of the remedial alternative that will be ultimately selected.
There are several technologies that can be considered for the discharge of treated
groundwater. These methods include discharge to a POTW; transport to a RCRA-permitted
treatment, storage, and/or disposal facility (TSDF); discharge to a surface-water body; conveyance
to a beneficial user for non-potable purposes; re-injection; or re-use for drinking water (potable
use). In some cases, these methods may or may not be coupled with treatment. The discharge
options at the Tutu Wells Site are considered only in combination with collection and treatment.
In this section, the effectiveness of each discharge option is evaluated, implementability
issues are reviewed, and the costs associated with implementing each discharge option are
evaluated. A summary of the technology screening of discharge options is provided in Table 4-3.
4.4.5.1 Discharge to Publicly Owned Treatment Works
Discharge of treated groundwater from a site to a local POTW is an established reliable
technology. This approach involves trucking extracted groundwater to a nearby treatment plant or
discharging treated groundwater to a sanitary collection system that conveys the discharge to the
local POTW. In either case, final discharge of the treated groundwater would be through the
outfall of the local POTW. Discharge of the water into the sewer system may require pretreatment
prior to its acceptance at the POTW. This technology is a common and effective way to dispose
treated groundwater.
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Based on Geraghty & Miller's review, the local POTW that services the Tutu Wells Site is
currently operating at capacity and cannot accept new discharges. There are plans for POTW
expansion in the near future that would make this approach easier to implement. However, these
plans are in the preliminary stages of development and cannot currently be considered in the
evaluations. Implementation of this technology would require local POTW expansion.
If available POTW treatment capacity existed, approvals would be needed from the US VI
Department of Public Works (DPW) for discharge into the sanitary sewer system. If the discharge
were to comprise a significant portion of the total flow into the local POTW, it is possible that the
treatment efficiency at the local POTW could be reduced. This could cause the DPW to object to
the discharge and require an alternative to be considered. Also, discharging treated groundwater to
the local POTW would not be an effective re-use of the treated groundwater, as the subsequent
discharge point would not replenish the Tutu aquifer.
The capital and O&M costs associated with this technology would be low to moderate,
depending on the level of treatment that would be required to meet permit limits. Geraghty &
Miller anticipates that treatment to background groundwater quality would be sufficient. There are
significant implementability issues that must be resolved prior to implementing this technology.
Since the current POTW does not have the capacity for the expected effluent flow rates
(approximately 100 gpm), discharge to the local POTW will not be considered for discharge of
treated water.
4.4.5.2 Discharge to a RCRA-Permitted Treatment, Storage, and/or Disposal Facility
Disposal at a RCRA TSDF is not an effective technology for the discharge of groundwater.
No facilities of this type operate on a commercial basis within the USVI. Implementing this
technology for groundwater treatment would involve off-island transport and disposal at a RCRA-
permitted TSDF in the mainland United States. This option would be administratively difficult to
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implement due to the transport of impacted groundwater off-island, and the costs associated with
executing the transport and disposal would be prohibitively high. 
For these reasons, this
technology will not be retained for further consideration.
4.4.5.3 Discharge to Surface Water
Discharge to a surface-water body is a potential technology for discharge of treated
groundwater at the Tutu Wells Site. The treated groundwater could potentially be discharged into
Turpentine Run, the stream that transects the Tutu Valley. 
Effectiveness of this disposal
technology would be favorable because there is a surface-water body that could effectively receive
the discharge of treated water
A surface-water discharge would require application for a Territorial Pollution Discharge
Elimination System (TPDES) permit. Discharge limits associated with the issuance of the permit
/*"*"v 
may be less stringent than MCL requirements, reducing the level of treatment that would be
required for potable discharge options. 
Review of background data collected by the U.S.
Geological Survey (USGS) (1973) indicates that surface-water quality in the vicinity of the Tutu
Wells Site is similar in background inorganic concentrations to that found in groundwater.
Therefore, treatment for inorganic water quality parameters should not be necessary unless it
affects the operation of the treatment system. Additionally, the effluent from the treatment system
may actually provide some benefit to existing conditions downstream, providing a continued
source of flow for the stream. Stationary wastewater treatment plants discharge downstream of
the proposed remedial alternative discharge and would provide some dilution of effluents
downstream.
An assessment of potential impact to a wetland identified by the USEPA will be needed.
Table 4-4 provides background water quality data from the USGS gauging station at Turpentine
Run at Mt. Zion. Effluent quality parameters similar to these could be established. Continual
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monitoring of the effluent quality would also be required to ensure compliance with the permit
limits.
The extraction of groundwater and subsequent discharge to the Turpentine Run would not
provide a beneficial re-use of treated groundwater in the Tutu Valley. However, surface water
could potentially recharge groundwater downstream of the point of discharge through infiltration
within the natural stream channels and would potentially become available for re-use downgradient.
Implementability issues exist with this technology, as a TPDES permit requires, at a
minimum, 12 to 18 months to secure, and negotiations with local regulatory agencies will be
regional. The costs to implement this option would be low to moderate, depending on the permit
limits that would have to be met. This option is technically implementable and will be retained for
further consideration.
4.4.5.4 Conveyance to Beneficial Non-Potable User
Another method for discharging extracted groundwater is re-use of the treated water for
beneficial non-potable use. 
This technology would be effective and provides a re-use of the
extracted groundwater in the study area.
This method would involve piping the treated groundwater to a point where it could be
distributed for commercial or industrial purposes or residential non-potable use. There are several
commercial users (e.g., laundromat, car wash, and concrete plant) in the area that could make use
of non-potable water, deriving a beneficial use for the groundwater resource.
This technology may be administratively difficult to implement. Treated groundwater use
would be required and would involve negotiations with several commercial users to ensure
continual use. A commitment for continual use of groundwater may be difficult for a commercial
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user to anticipate, as commercial groundwater uses could vary throughout the year. Conversely,
the collection and containment objectives for the groundwater pumpage would require nearly
continuous operation.
The treatment requirements associated with this discharge option would not be as stringent
as compliance to MCLs, but the water would require treatment to background water quality at a
minimum. The costs associated with implementation would be moderate.
This option will not be retained for further consideration in this FS Report due to the
implementability issues associated with finding a beneficial user that could accept the anticipated
flow rate.
4.4.5.5 Re-Injection
/*—N 
Re-injection of treated groundwater would involve discharging treated groundwater into
injection wells or infiltration galleries where it could be introduced back into the aquifer. This may
not be as effective as other options depending on how and where it is implemented.
This technology would allow re-use of extracted groundwater, through infiltration and
recharge, and may also enhance groundwater remediation, by enhancing the flushing action caused
by continual pumping. Re-injection could be accomplished in several ways; the two most common
methods are shallow re-injection through the use of infiltration trenches or galleries, and deeper re-
injection through the use of re-injection wells.
The use of re-injection wells would be difficult to implement due to the anisotropic
conditions of the underlying fractured bedrock. O&M costs would be high due to the potential for
plugging of reinjection wells with precipitation and biological growths. If infiltration galleries are
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used, a sufficient area would be required for construction of the disposal beds. The effect of
recharge or groundwater flow in the bedrock aquifer would be difficult to monitor and control.
This type of disposal would require a TPDES permit to discharge to groundwater and
could require treatment of the extracted groundwater to MCLs. The anticipated time frame
required to secure a permit to discharge to groundwater would be approximately 12 to 18 months.
Due to limitations of maintaining hydraulic control during injection into an anisotropic and
complex aquifer, and high associated O&M costs, this technology will not be considered for further
evaluation.
4.4.5.6 Distribution for Potable Use
The most direct beneficial re-use option is providing groundwater for potable use to
residents. This would be an effective discharge option, would involve re-use of groundwater in the
Tutu Wells Site, and would provide an additional drinking water source in St. Thomas. Beneficial
re-use for potable use is an important consideration on St. Thomas due to the limited water supply
resources available on the island.
After treatment, groundwater would be stored, tested, and distributed to residential users,
either through distribution mains or trucking, for potable water use. The local water purveyor, the
WAPA, has a distribution system in place and is planning to improve the distribution system in the
vicinity of the Tutu Wells Site. 
A direct connection to this system is feasible, possibly
supplemented by a storage tank, to provide additional storage that could be used during high
demand periods. During periods of low use, the treated water could be discharged to waste, either
directly or through storage tank overflow.
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Potable use would require treatment of extracted groundwater to remove inorganic
constituents that are naturally occurring in the valley, such as total dissolved solids (TDS), in
excess of secondary MCLs. Treatment of inorganic constituents would increase the complexity of
the treatment facility required and could double the capital costs for treatment when compared to
the costs associated with non-potable use. Annual O&M costs would also increase, due to the
added requirement of sludge handling and disposal.
Discharge of treated groundwater into the public water supply system would also create
administrative issues. Approvals would be needed from the WAPA, and stringent effluent
discharge requirements would have to be met. Treatment to meet MCL requirements would have
to be provided. Requirements for testing of the treated water prior to distribution could also be
required. For cost-estimate purposes, Geraghty & Miller has assumed that a 2-day turnaround of
treated water analyses would be conducted and a 3-day storage capacity would be provided to
allow for confirmation of acceptable potable water quality prior to distribution. In order to better
evaluate the cost for this potentially important discharge option, Geraghty & Miller prepared a
detailed cost estimate for a typical groundwater remedial alternative using a potable use discharge
option for the Tutu Wells Site. Appendix A provides a cost estimate for the potable use discharge
option.
Capital and O&M costs would be significantly higher than other discharge technologies
due to the increased level of treatment required. Due to the implementability issues associated with
this technology and the high cost, it will not be retained for further consideration.
4.5 TECHNOLOGIES RETAINED FOR FURTHER CONSIDERATION
A number of potentially suitable and feasible remedial technologies have been identified and
subjected to a screening process in accordance with the USEPA guidance (USEPA 1988a). The
outcome of this process was the selection of several remedial technologies and process options for
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soil and groundwater that will be retained for further consideration. The following technologies
were retained for remediation of soil and groundwater underlying the Tutu Wells Site:
SoU
• No Action
• 
Institutional Controls
Access Restrictions
Deed Restrictions
• 
Containment
Capping
• 
In-Situ Treatment
In-Situ Soil Vapor Extraction (SVE)
Bioventing
• 
Ex-Situ Treatment
SVE Treatment
Biopiles
• 
Removal and Disposal
Excavation and Off-Site Disposal
Excavation On-Site Treatment and On-Site Disposal
Groundwater
• No Action
• 
Institutional Controls
Access Restrictions
Deed Restrictions
• 
Alternate Water Supply
Trucking Water
Public Water Supply Extension
• 
Collection/Containment
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Extraction
Extraction Wells
• 
In-Situ Treatment
Air-Sparging
Bio-Sparging
• 
Ex-Situ Treatment
Air Stripping
GAC Adsorption
Filtration
Precipitation/Flocculation/Sedimentation
Reverse Osmosis
Ion Exchange
UV Oxidation/Reduction
GAC Fluidized Bed
• 
Natural Remediation
• Discharge
Discharge to Surface Water
The soil and groundwater technologies listed above have survived screening and may be
applicable for remedial applications at the Tutu Wells Site. These screened technologies could be
applied separately or in conjunction as a system. For the purposes of this FS Report, representative
assemblies of the most effective technologies are compiled for comparison purposes. As indicated
by FS guidance (USEPA 1988a), the cost difference between different process options will not
significantly affect the overall comparison of remedial alternatives. For soil, the following
representative technologies are used:
• 
Capping.
• 
In-situ SVE/bioventing.
• 
Ex-situ S VE/biopiles and onsite disposal.
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• 
Excavation and offsite disposal.
For groundwater, the following representative technologies are used:
• 
Collection/containment.
• 
Ex-situ treatment using air stripping and GAC adsorption.
4.6 
FURTHER EVALUATION OF SCREENED TECHNOLOGIES
The technologies identified in Section 4.5 (Technologies Retained for Further
Consideration) are further evaluated in this section. Site-specific characteristics are considered to
recommend a specific remedial technology for soil and groundwater. Soil remedial alternatives are
evaluated for individual properties. Groundwater remedial alternatives are discussed on a site-wide
basis. In addition, Source Control Plans (SCPs) for soil and groundwater contamination near the
Texaco and Esso service stations are discussed for consistency, scheduling, and coordination of
proposed remedial actions. The technologies considered for further evaluation in this FS are those
best suited to address the overall environmental concerns at the Tutu Wells Site and to meet the
RAOs.
4.6.1 Source Control Plans
Implementation of SCPs has been proposed at the Texaco Tutu Service Station and the
Esso Tutu Service Station. In this section, a summary description is provided to describe each
SCPs. 
More detailed descriptions of these remedial alternatives have been prepared by
independent consultants and have been, or will be, submitted to the USEPA under separate cover.
Discussions of the SCPs in this FS are limited to a conceptual evaluation of the technologies
proposed. The effect of these SCPs on the planned site-wide remediation at the Tutu Wells Site is
also evaluated in this FS.
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4.6.1.1 Texaco Tutu Service Station Source Control Plan
Groundwater extraction wells will be installed at the downgradient property line of the
Texaco Tutu Service Station to remediate and contain the migration of petroleum compounds
dissolved in groundwater. It is estimated that total groundwater pumpage necessary for optimum
capture of BTEX at the Texaco facility will be approximately 20 gpm. Groundwater will also be
extracted from a well near the northern boundary of the Vitelco property to remediate and control
the further migration of the portion of the petroleum hydrocarbon plume that is downgradient of
the service station. This proposed extraction well at the Vitelco property will be pumped at a rate
of approximately 10 gpm. The combined pumpage for the Texaco SCP will be approximately 30
gpm. At each groundwater extraction location, the groundwater will be routed to treatment units
housed in a cargo container. Extracted groundwater will be treated by air stripping to achieve
compliance with Federal Drinking Water MCLs. The treated water will be discharged to the storm
sewer under a TPDES permit.
At the Texaco Tutu Service Station, an SVE system (consisting of SVE wells installed in
the vicinity of the former tank excavation) will remediate soil that may contain high concentrations
of petroleum hydrocarbons. Cat-ox will be used to provide off-gas control.
The SCPs proposed at the Texaco Tutu Service Station can be effective at remediating soil
at the site and can provide effective capture of the source area for groundwater impacted by
petroleum hydrocarbons. The technologies presented are in conformance with those screened in
the FS and can be optimized and refined during operation to maximize remediation of the source
area.
4.6.1.2 Esso Tutu Service Station Source Control Flan
SCPs will be implemented at the Esso Tutu Service Station. Groundwater will be extracted
from four shallow recovery wells (presently assumed to be existing Monitoring Wells MW-9 or
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CHT-2, SW-7, SW-1, and CHT-3) on or near the Esso property. Available site hydraulic data
indicate that the combined groundwater withdrawal rate from these wells will range from 5 to 15
gpm. Extracted groundwater will be treated on-site through an existing air stripping and GAC
system. Treated groundwater will ultimately be discharged, under a TPDES permit, to the storm
sewer beneath the Four Winds Plaza (Turpentine Run). Given prior mass loading calculations and
permit requirements, it has been assumed that a de minimis waiver can be obtained for untreated air
stripper off-gas.
Pending site pilot studies, bioventing and biosparging may be incorporated into the Esso
SCPs to elevate oxygen levels and increase the biodegradation of dissolved COCs. Residual soil
impact will be addressed through an integrated bioventing and SVE program. The conceptual
design for this system presently incorporates two horizontal vapor extraction trenches and a
minimum of four biosparging wells. One vapor extraction trench will be positioned adjacent to the
north oil/water separator. The second trench will be installed near the pump island. Off-gas
treatment will be evaluated further in the pre-design phases of implementation.
The SCPs proposed at the Esso Tutu Service Station can be effective at remediating soil at
the site and can provide effective capture of the source area for groundwater impacted by
petroleum hydrocarbons. The technologies presented are in compliance with those screened in the
FS and can be optimized during the operation to maximize remediation of the source area.
4.6.2 Soil Remedial Technologies
Geraghty& Miller has compared the soil data collected during the RI to the SSLs
established for soil at the Tutu Wells Site (see Table 2-4). Seven sites have been identified as
potentially requiring remedial action for soil; these sites are the Curriculum Center, Ramsay
Motors, Texaco Tutu Service Station, Tillett Gardens, Western Auto, Esso Tutu Service Station,
and OHenry Dry Cleaners. The potential need for remediation at Tillett Gardens was identified in
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the Baseline Risk Assessment (CDM Federal Programs Corporation 1995a). Table 4-5 identifies
the properties potentially requiring soil remediation, the contaminants at each property that exceed
SSLs, and the areas and estimated soil volumes potentially requiring remediation.
The remedial technologies for soil that were retained based on initial screening were listed
in Section 4.5 (Technologies Retained for Further Consideration). These remedial technologies
were considered on a property-specific basis to evaluate the application of these technologies to the
specific site conditions. A few of the technologies or process options were combined during the
evaluation. For example, No Action and Institutional Controls were combined because if the No
Action alternative was selected, Institutional Controls would be required to be implemented in
conjunction with the No Action alternative (see Table 4-6).
Capping of soil containing contaminants above acceptable levels is generally applicable to
all areas of the Tutu Wells Site. Capping may consist of (1) continued maintenance of existing
concrete or asphalt paving or (2) installation of a new cap (see Table 4-7).
The in-situ treatment technologies (In-Situ SVE and Bioventing) and the ex-situ treatment
technologies (Ex-Situ SVE and Biopiles) were combined for this property-specific evaluation (see
Tables 4-8 and 4-9). The selection of in-situ or ex-situ treatment for soil is a fundamental decision
based on the COCs present and site conditions such as volume (which determines cost-
effectiveness), building foundations and physical access (which affects implementability), and
subsurface conditions, such as soil type (which affects the potential effectiveness).
Regardless of whether in-situ or ex-situ treatment is selected, the treatment methods will be
selected based on the contaminants present. SVE (in-situ or ex-situ) will be effective in reducing
both chlorinated VOCs and BTEX constituents. However, bioventing (in-situ) and biopiles (ex-
situ) would provide an additional treatment option for BTEX constituents.
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^—x 
Excavation and disposal of impacted soil at affected properties would result in complete
removal of the impacted areas from the Tutu Wells Site (see Table 4-10). The excavated soil
would be classified as either hazardous or non-hazardous waste through laboratory testing of
representative samples by Toxicity Characteristic Leaching Procedure (TCLP) methods. If deemed
hazardous, comparison of laboratory results with contaminant levels identified in the federal Land
Disposal Restrictions (LDRs) would determine if land disposal is allowable. If the material
excavated is considered non-hazardous, the material would be disposed at the Bovoni landfill
located approximately 2 miles southwest of the Tutu Wells Site. This is the only disposal option on
St. Thomas, and this option would require extensive testing to demonstrate the material is non-
hazardous. If the excavated material is considered hazardous, the material would be shipped for
treatment and for disposal at an approved hazardous waste facility off-island. For the purposes of
cost estimates, this FS Report includes disposal costs based on disposal as a hazardous material.
In addition to the property-specific evaluation of technologies presented in Tables 4-6
through 4-10, each property is discussed further below. Based on the specific site conditions, the
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remedial technologies for soil will be compiled into Soil Remedial Alternatives (SRAs), which
represent an assembly of applicable soil technologies to derive site-wide remedial alternatives.
4.6.2.1 Curriculum Center
Soil sampling conducted during the RI at the Curriculum Center indicated the presence of
BTEX constituents above SSLs in the vicinity of the northeast comer of the Curriculum Center
building (see Figure 4-1). Chlorinated VOCs (including PCE) have been detected in soil and soil
gas at the north and northwest portions of the building, but were not found in soil above the SSLs
during the RI. However, chlorinated VOCs may be present at higher concentrations in the
unsaturated bedrock (which was not sampled) underlying the property, as suggested by the high
chlorinated VOC concentrations in the groundwater near and downgradient of the Curriculum
Center.
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Due to the shallow depth to bedrock and the limited extent of BTEX-impacted soils,
excavation and disposal is proposed at the northeast corner of the Curriculum Center. Excavation
and ex-situ treatment on-site will also be considered; however it may be more expensive to
implement due to the relatively low soil volume (see Table 4-5).
To remediate the potential presence of DNAPLs in the unsaturated bedrock, an SVE
program is being considered for implementation at the Curriculum Center. SVE is a presumptive
remedy for VOC contamination. Capping can also be implemented at the soil surface to reduce a
groundwater infiltration into the unsaturated bedrock, thus reducing the leaching of contaminants
to groundwater. The bedrock surface is relatively shallow at the Curriculum Center, making
capping potentially applicable to controlling the impact of DNAPLs in unsaturated bedrock.
Additional property characterization of a remedy would be required to determine the potential
locations of DNAPLs prior to implementation. The potential locations of soil remediation and
bedrock remediation at the Curriculum Center are shown on Figure 4-1. 
Preliminary SVE well
locations are based on a soil gas survey performed by Geraghty & Miller (Geraghty & Miller, Inc.
1995). These locations would have to be better defined by further drilling and sampling in
suspected source areas prior to implementation of this remedial technology.
4.6.2.2 Ramsay Motors
Soil impacted by BTEX has been detected above the SSLs near the waste oil UST beneath
the Ramsay Motors maintenance garage (see Figure 4-2). Groundwater samples collected from
downgradient monitoring wells did not show the presence of BTEX compounds during the RI.
The small volume of potential soil for remediation makes capping the most cost-effective
technology. Because existing cracks in the concrete may allow for infiltration of rainfall and
surface spills, the floor slab would need to be removed and replaced to provide an appropriate cap.
Due to the location of the waste oil UST beneath the concrete floor slab of the maintenance
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garage, excavation for soil remediation is not considered cost-effective because it would require
complete demolition of the building. If downgradient monitoring wells continue to show no
presence of BTEX constituents, capping (i.e., replacement of the concrete floor) would be the
most effective soil remedy.
4.6.2.3 Texaco Tutu Service Station
Soil impacted by BTEX constituents was found at the Texaco Tutu Service Station. The
unconsolidated deposits and the upper portion of the fractured bedrock underlying the Texaco
Tutu Service Station are relatively permeable and could be treated in-situ with either SVE or
bioventing. Due to the high vapor pressure of BTEX constituents, SVE is considered the preferred
in-situ treatment alternative of the two. Also, SVE tends to enhance biodegradation of BTEX
constituents, in addition to volatilization of BTEX. The small volume of impacted soil may make
excavation and disposal a more economical alternative than in-situ treatment. Ex-situ treatment of
excavated soil prior to disposal on-site could also be considered; however, the small volume of
impacted soil may make the cost of on-site ex-situ treatment prohibitive. The potential locations of
soil remediation at the Texaco Tutu Service Station are shown on Figure 4-3. A SCP currently
being prepared for implementation at the Texaco Tutu Service Station was discussed in Section
4.6.1.1 (Texaco Tutu Service Station Source Control Plans).
4.6.2.4 THIett Gardens
In the USEPA's Baseline Risk Assessment (COM Federal Programs Corporation 1995a),
arsenic and PCBs were determined to be present in soil at Tillett Gardens at concentrations above
safe exposure levels. Due to the small volume of impacted soil identified, capping or excavation
and disposal are the only alternatives considered viable. Figure 4-4 illustrates the potential location
of remediation for Tillett Gardens.
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4.6.2.5 Western Auto
The soil near Western Auto location was impacted by BTEX constituents. Previous UST
removals were completed by Western Auto (ENSR Consulting and Engineering [ENSR] 1994);
the available data suggest that impacted soil may still be present in that area. The soil in the vicinity
of the former USTs consists primarily of clay with a relatively low permeability and would not be a
suitable medium for in-situ remediation. SVE and bioventing are not considered viable and will not
be considered at the Western Auto property. It is likely that clumps of excavated clay would
require extensive pulverization and reworking prior to attempting on-site treatment. Because of
the low permeability clay, excavation and on-site ex-situ treatment are also considered ineffective.
Excavation and disposal and capping of the impacted soil at the Western Auto facility are
the only two options considered. Excavation and disposal may be difficult to implement due to the
need to excavate close to existing buildings. In addition, work should also include removal or
elimination of potential source areas as defined in previous studies (ENSR 1994; Geraghty &
Miller, Inc. 1995). Buried 4-inch diameter PVC piping may be a potential source and should be
investigated further. For the purposes of this FS, a 2-foot thick layer of soil extending 2.5 feet east
and west of the PVC pipe was assumed to require remediation. This PVC pipe is not related to
Western Auto operations. However, the further investigation and possible remediation of the PVC
pipe should be coordinated with Western Auto due to the proximity of the PVC pipe and the
former Western Auto USTs. The areas where remediation is potentially required near the Western
Auto facility are illustrated on Figure 4-5. The shaded area on this figure encompasses an area
where soil was previously removed as part of the UST removal. A credit for removal of 35 cubic
yards of soil related to the prior UST closure was included in the cost evaluation. Geraghty &
Miller has assumed that the 35 cubic yards of clean backfill may need to be excavated, but this
volume will not require treatment or disposal. Further pre-design work is needed to determine if
additional soil remedial measures are appropriate.
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4.6.2.6 Esso Tutu Service Station
Constituents detected in soil in the area of the Esso Tutu Service Station consist of VOCs,
primarily BTEX constituents. Chlorinated VOCs were detected in soil in the western portion of
the Esso property.
Shallow unconsolidated deposits at the Esso Tutu Service Station consist primarily of
relatively coarse gravel fill material and may be appropriate for S VE. Bioventing in the vicinity of
the north oil/water separator would not be appropriate due to the presence of chlorinated VOCs,
which are not readily biodegradable under aerobic conditions. BTEX constituents are easily
removed through the application of SVE or bioventing. Also, SVE tends to enhance
biodegradation of BTEX constituents, in addition to volatilization of BTEX. SVE would be
preferred and would be faster than bioventing. Due to the presence of the building foundation,
excavation options would be difficult to implement, but are potentially implementable. SVE is
therefore considered as the preferred alternative with localized areas that may be suitable for
bioventing. Figure 4-6 illustrates the areas to be considered for remediation at the Esso Tutu
Service Station. Soil concentrations above SSLs reported in Borings B-101 and B-102 may be due
to the presence of perched water that may contain dissolved contaminants in the aqueous phase.
Additional soil sampling and investigation will be implemented as part of the pending SCP for the
Esso property. A SCPs currently being prepared for implementation was discussed previously in
Section 4.6.1.2 (Esso Tutu Service Station Source Control Plan).
4.6.2.7 O'Henry Dry Cleaners
PCE concentrations above the SSLs were detected in soil at the southeast comer of the
building; these concentrations were the highest concentrations of chlorinated VOCs observed
throughout the Tutu Wells Site. The shallow unconsolidated deposits underlying the O'Henry Dry
Cleaners are relatively permeable and could be remediated using SVE. PCE is readily removed
using SVE. Bioventing is not effective in the treatment of halogenated VOCs; therefore, bioventing
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will not be considered farther. Even though in-situ SVE would be applicable, the small volume of
impacted soil may make excavation and disposal a more economical alternative than in-situ
treatment. Ex-situ application of SVE may also be appropriate. Four soil remedies are evaluated
for the OHenry Dry Cleaners, including (1) capping, (2) in-situ SVE treatment, (3) excavation,
ex-situ SVE treatment, and on-site disposal, and (4) excavation and off-site disposal. Figure 4-7
illustrates the locations potentially requiring remediation at the OHenry Dry Cleaners.
To remediate the potential presence of DNAPLs in the unsaturated bedrock, an SVE
program is being considered for implementation at the OHenry Dry Cleaners. 
SVE is a
presumptive remedy for VOC contamination. Capping can also be implemented at the soil surface
to reduce infiltration of precipitation into the unsaturated bedrock, thus reducing the leaching of
contaminants to groundwater. Additional property characterization of a remedy would be required
to determine the potential locations of DNAPLs prior to implementation. The potential locations
of soil remediation and bedrock remediation at the OHenry Dry Cleaners are shown on Figure 4-7.
These locations will have to be better defined by farther drilling and sampling in suspected source
areas prior to implementation of this remedial technology.
4.6.3 Groundwater Remedial Alternatives
Both in-situ and ex-situ treatment technologies for groundwater remediation have been
retained for consideration. However, due to the complex and anisotropic fractured bedrock aquifer
that underlies the site, in-situ treatment is not considered viable for site-wide groundwater
treatment. The only in-situ technology retained for consideration is biosparging, which will be
evaluated on a site-by-site basis for remediation of BTEX constituents in shallow groundwater.
More conventional groundwater extraction and ex-situ treatment technologies will be considered,
including air stripping, GAC adsorption, filtration, precipitation/flocculation, sedimentation, ion
exchange, chemical oxidation/reduction, fluidized bed/GAC, natural remediation, and well head
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treatment. These treatment technologies will be considered in conjunction with three general
groundwater collection and containment extraction well approaches, as follows:
• 
Source Containment and Point-of-Entry Treatment Systems (POETs).
• 
Plume Containment.
• 
Source and Plume Containment.
The technology screening for discharge options from ex-situ groundwater treatment
systems in Section 4.4.5 (Discharge) resulted in the selection of discharge to surface water as the
preferred option.
SCPs are proposed for implementation at the Texaco Tutu Service Station and the Esso
Tutu Service Station to treat and contain the plumes related to the groundwater contamination
with BTEX constituents at each of these properties (see Figure 4-8). These SCPs will be initiated
prior to the complete FS remedy. Data collected during operation of these Source Control
Systems will be analyzed as part of the design phase for the FS remedy. However, implementation
of SCPs at the service stations has been considered to ensure that they are compatible with the
groundwater remedial alternatives (GRAs) proposed in this FS Report. Those SCPs include
discharge to Turpentine Run via a TPDES permit.
4.6.3.1 Collection and Containment
The RAOs identified two criteria that each groundwater containment scenario must meet,
as follows: (1) minimize the upconing of mineralized groundwater from deeper portions of the
aquifer, and (2) not exceed the maximum safe yield of the aquifer. Based on an estimated
catchment area of 1.08 square miles (upgradient of potential recovery wells) and an aquifer
recharge rate of 3.3 inches per year (Jordan and Fisher 1977), Geraghty & Miller has estimated the
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maximum safe yield for the Tutu Wells Site area to be approximately 118 gpm, assuming continual
pumpage (24 hours/day, 365 days/year).
After consideration of GRA 1 (No Action/Industrial Controls), three groundwater
recovery scenarios have been assembled for evaluation. The preferred scenario for groundwater
collection and containment is to use several groundwater recovery wells strategically placed
throughout the Tutu Wells Site. For purposes of this FS, three potential plume containment
recovery wells, Recovery Wells RW-1, RW-2, and RW-3, are proposed. Recovery Well RW-1 is
envisioned at the southern end of the northern chlorinated VOC plume, and Recovery Wells RW-2
and RW-3 are envisioned at the southern end of the southern chlorinated VOC plume. Similarly,
two potential source containment wells, Recovery Wells RW-4 and RW-5, 
are proposed.
Recovery Well RW-4 is envisioned at the downgradient edge of the Curriculum Center property,
and Recovery Well RW-5 is envisioned at the downgradient edge of the O"Henry property (see
Figure 4-9).
Containment of impacted groundwater will be achieved by implementing one of the
following recovery well system scenarios. Each scenario is associated with a specific GRA, and
each scenario has been named after the type of wells that are emphasized (i.e., pumped at
maximum rates) in that scenario. In addition to GRA 1 (No Action/Institutional Controls), the
proposed GRAs are briefly described below and evaluated further in Section 5.3 (Development and
Evaluation of Remedial Alternatives for Groundwater).
• 
GRA 2 - Source Containment and POETs
In this scenario, Recovery Wells RW-4 and RW-5 would be pumped at 20 gpm and 35
gpm, respectively, to achieve containment of groundwater with high concentrations of
chlorinated VOCs near the contaminant sources. For cost comparison with other
GRAs, these wells were assumed to pump to a common influent feed line and then to a
central treatment facility. The maximum total groundwater pumpage to the treatment
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system would be 55 gpm. Existing private supply wells (situated at locations that
could provide effective plume containment) would be equipped with POET systems
and pumped to provide containment of the VOC plumes beyond the source
containment wells. Geraghty & Miller has assumed that the maximum total extraction
from private wells would be 15 gpm. This pumping rate for supply wells assumes an
average pumpage of 1.25 gpm from each of four residential wells (i.e., Steele, La
Place, Smith, and Matthias) and 10 gpm from one commercial supply well, Four
Winds! Estimated maximum pumpage associated with the Texaco Tutu Service
Station and Esso Tutu Service Station SCPs would be 30 gpm and 10 gpm,
respectively. The maximum total groundwater pumpage for this scenario (GRA 2)
would be 110 gpm (see Table 4-11).
GRA 3 - Plume Containment
This scenario involves pumping of three plume containment wells (Recovery Wells
RW-1, RW-2, and RW-3). Groundwater would be pumped to a common influent feed
line and then to a central treatment facility. Proposed Recovery Wells RW-1, RW-2,
and RW-3 would be pumped at maximum rates of 15 gpm each, for a total of 45 gpm
for these three plume containment wells. Existing supply wells would not be pumped
in this scenario. The Texaco Tutu Service Station and Esso Tutu Service Station
source control wells are assumed to pump at estimated maximum total rates of 30 gpm
and 10 gpm, respectively. The maximum groundwater pumpage under this scenario
would be 85 gpm (see Table 4-11).
GRA 4 - Source and Plume Containment
In this scenario, the plume containment wells and source control wells (all five potential
recovery wells) would be pumped to a common influent feed and then to a central
treatment facility. Recovery Wells RW-1 through RW-3 would each be pumped at a
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rate of 15 gpm; Recovery Wells RW-4 and RW-5 would be pumped at approximately
20 gpm and 35 gpm, respectively. The maximum total groundwater pumpage from
recovery wells would be 100 gpm. The 40 gpm total for the source control pumpage
at the Texaco Tutu Service Station (30 gpm) and Esso Tutu Service Station (10 gpm)
would bring the overall maximum pumpage rate to 140 gpm, which exceeds the
estimated safe yield of the catchment area of 118 gpm (see Table 4-11). It should be
noted, however, that there is a significant difference in the anticipated time frames for
pumpage of the site-wide plume containment and source containment wells compared
to the extraction wells associated with the SCPs at the two service stations. Due to the
small size of the BTEX plumes and the biodegradable nature of BTEX constituents,
Geraghty & Miller anticipates that the SCPs will achieve their remedial goals in 3 to 7
years of operation. In contrast, it is envisioned that the site-wide recovery wells will
likely have to operate for much longer time periods (on the order of 10 to 30 years),
due to the large areas of the chlorinated VOC plumes and the potential for the
existence of DNAPLs at two source areas.
Geraghty & Miller anticipates that the SCPs will be implemented in 1995 or early 1996,
while the site-wide groundwater remedy will not be implemented until late 1996 or 1997, allowing
time for public comment on the selected remedy and pre-design work. Therefore, it is possible that
the SCPs will be near completion when the site-wide groundwater remedy is implemented.
Pumping rates can be adjusted during any period of overlap to maintain overall capture of
contaminants and to maintain total pumpage below the estimated safe yield of the aquifer in the
affected area. If the SCP groundwater pumpage is reduced, the site-wide groundwater recovery
wells will provide collection and containment for the BTEX constituents in groundwater.
However, the SCP pumpage should be maintained as much as possible to provide more effective
withdrawal of the BTEX constituents.
Geraghty & Miller has assumed that all the proposed recovery wells will be installed to a
depth of approximately 150 feet bis and will be screened across the shallow and deep portions of
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the bedrock aquifer (i.e., My penetrating). The depth of 150 feet bis was selected to maximize the
complete penetration of the aquifer without intercepting the deeper portions of the aquifer that
contain mineralized water. Deep mineralized water contains elevated TDS and chloride. If drawn
upward by pumpage, the mineralized water could degrade the quality of shallow groundwater. This
mineralized water could also accelerate corrosion and fouling of the recovery and treatment
systems. Therefore, a depth of 150 feet bis was selected as the optimum depth for recovery wells
for the chlorinated VOC-impacted groundwater. For areas where impacted groundwater may
occur below 150 feet bis, Geraghty & Miller has assumed that upward groundwater flow induced
by recovery well pumpage and natural attenuation will remediate the deeper portions of the aquifer
over time.
The locations of the proposed recovery wells were based on a preliminary capture zone
analysis, which is summarized in Appendix B. Estimated capture zones for proposed SCPs at the
Texaco Tutu and Esso Tutu Service Stations are illustrated on Figure 4-8, with the shallow
groundwater contour map and the BTEX concentrations in groundwater contours. Estimated
capture zones at maximum pumping rates in GRA 2 and GRA 3 and proposed groundwater
recovery well locations are illustrated on Figure 4-10. The proposed groundwater recovery well
locations for GRA 4 are illustrated on Figure 4-9. The pumping rates of the proposed recovery
wells under the different GRAs evaluated are summarized in Table 4-11.
4.6.3.2 Treatment
In this section further evaluations of treatment technologies are provided. The potential
effectiveness of in-situ treatment technologies (i.e., air-sparging and bio-sparging) that survived
screening is difficult to evaluate without site-specific pilot testing, especially in a heterogeneous
matrix of fractured bedrock. This FS Report allows the possibility for these technologies to be
evaluated further because they may be beneficial. Because the effectiveness and associated costs
are not well known, air-sparging and bio-sparging have not been included in the groundwater
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remedial alternatives assembled for comparison in this FS Report. 
In this section, further
evaluations of the ex-situ treatment schemes for a central treatment facility and for the proposed
POET systems are provided. In Section 4.6.3.3 (Natural Remediation), the basis for applying
natural remediation in the downgradient (i.e., southeastern) portion of the chlorinated VOC plume
are discussed.
Each collection and containment option discussed in Section 4.6.3.1 (Collection and
Containment) will be associated with a central treatment facility. The central treatment facility will
consist of one or more of the ex-situ groundwater treatment technologies that were retained from
the initial screening. The technologies chosen for a central treatment facility are contingent on
several factors, including existing performance data and the type of contaminants, and the
concentration of contaminants present in the extracted groundwater.
Similar to soil, SCPs for groundwater treatment are proposed for implementation at the
Texaco Tutu Service Station and the Esso Tutu Service Station. These SCPs consider similar
treatment technologies and discharge options to those considered in this FS. 
No further
groundwater treatment options are considered for the Texaco Tutu Service Station and the Esso
Tutu Service Station. These SCPs were previously described in Section 4.6.1.1 (Texaco Tutu
Service Station Source Control Plan), and Section 4.6.1.2 (Esso Tutu Service Station Source
Control Plan).
Existing performance data related to a treatment system located on the Esso Tutu Service
Station property indicate that an air stripper combined with GAC polishing (of the aqueous
effluent) is an effective treatment method for groundwater at the Tutu Wells Site. These
technologies, used separately or in combination, are effective methods for VOC removal and can
be applied to all the pumping options considered.
Groundwater quality data have been collected throughout the Tutu Wells Site. Although
these data may not be an accurate indicator of the influent groundwater quality from a recovery
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well, this information can be used to estimate influent groundwater quality to a central treatment
facility.
Influent groundwater quality to each treatment facility was determined by using a mass
flow balance, averaging the flow rate and contaminant concentration for each collection and
containment well scenario. This predicted groundwater quality was evaluated against the MCL
primary and secondary standards to determine the level of treatment that may be required. In some
instances, secondary standard variances may be appropriate for some parameters, such as IDS,
since elevated levels of some naturally occurring inorganic parameters are common in the USVI.
The influent levels of contamination will vary with each collection and containment well scenario,
as different recovery wells may be used and flows from the recovery wells would be combined
prior to treatment; however, groundwater quality between scenarios would not vary enough to
warrant consideration of different treatment facility schemes. Table 4-4 provides a summary of the
predicted groundwater quality compared to MCLs for the Source Containment and POETs
scenario (GRA 2), the Plume Containment scenario (GRA 3), and the Source and Plume
Containment scenario (GRA 4). The estimated influent concentrations in Table 4-4 represent
weighted averages for the blended wells based on (1) groundwater quality near the proposed
recovery wells and (2) the estimated flow rate from each well.
One treatment scheme has been developed for a central treatment facility (i.e., discharge to
surface water). This scheme is based on the level of treatment required for this discharge option.
The primary reason for installing the central treatment facility is to remove the COCs identified in
the RI (Geraghty & Miller, Inc. 1995). Therefore, VOC treatment and removal, consisting of air
stripping and potentially GAC polishing, is included in this treatment scheme. Air stripping and
GAC adsorption are selected as representative technologies for cost comparison purposes in this
FS Report. Other treatment technologies that survived screening (e.g., filtration, reverse osmosis,
ion exchange) are viable technologies that are typically used for treatment of inorganic constituents.
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The groundwater treatment scheme shown on Figure 4-11 treats the groundwater to
background groundwater quality and does not address naturally occurring inorganic constituents
that are present above secondary MCLs (e.g., TDS and chloride). The treatment scheme proposed
for the central treatment facility assumes that chemical sequestering of the dissolved constituents
can be achieved successfully. This assumption is based on the assumed hardness, iron, and
manganese concentrations in the influent to the central treatment facility, and on the assumption
that the concentrations of these constituents are slightly below the maximum point where
sequestering can still be achieved. If actual hardness, iron, and manganese concentrations are
higher than assumed, sequestering may not be implementable. Modifications to the pre-treatment
scheme may be required depending on the accuracy of these assumptions. This groundwater
treatment option is also considered applicable for a surface-water discharge option; however,
chemical feed rates or level of treatment may need to be modified to meet TPDES requirements.
These modifications should not significantly change the treatment scheme or cost. Treatability
testing, including a pilot test with actual groundwater recovery well samples, may be a required
step in the pre-design phase.
Even if the assumptions made for groundwater quality and level of treatment are not
confirmed during pilot testing or during the final design phases of implementation of the selected
GRA, the new data will not likely change the findings of this FS. In other words, evaluation of
new results would most likely be consistent for each GRA, since the costs for each option will be
increased by approximately the same amount.
POET systems are a form of treatment that will be considered as a groundwater treatment
method in this FS. POET systems refer to low capacity package groundwater treatment systems,
that are designed to be a low-maintenance and reliable form of treatment for individual wells. The
term POET indicates that treatment will be provided at the point of entry to a residence rather than
at the point of use (i.e., at the wellhead rather than at the drinking fountain). The POET systems
utilize either air stripping or GAC technologies and will be selected based on the anticipated
maximum pumping rate of each well, expected TDS concentrations, and the COC concentrations
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expected. A summary of the potential POET supply well installations is provided in Table 4-12.
Due to the maximum safe yield for the catchment area of 118 gpm and the pumpage of recovery
wells, the maximum total average flow of all the POET supply wells that could be allowed is
estimated to be approximately 15 gpm. This average flow allows for typical residential usage of
the five supply wells that were selected for POET installation based on their location in the central
portion of the groundwater plumes.
4.6.3.3 Natural Remediation
Proposed groundwater remedial alternatives are designed to capture the majority of the
chlorinated VOCs. The SCPs are designed to control BTEX. Due to aquifer safe yield limitations
on total pumpage and to optimize groundwater recovery efforts, lower concentrations of total
chlorinated VOCs (i.e., less than 100 ug/L) will not be recovered, rather these concentrations will
be allowed to attenuate and degrade naturally. A portion of the plume with chlorinated VOC
concentrations less than 100 ug/L may not be completely contained and will migrate downgradient
to the southeast. The following calculations (using half-lives and groundwater flow velocities) are
presented to estimate the time required for natural remediation to be effective at reducing
chlorinated VOC concentrations to MCLs.
Table 4-13 presents a summary of published half-lives for COCs in groundwater (Howard
et al. 1991). A half-life represents the amount of time required for natural degradation to reduce a
concentration to one-half of the initial concentration. The degradation rates and concentrations on
Table 4-14 are based on a first order decay of unimolecular constituents. These half-lives are based
on estimated rates of aerobic degradation of COCs in groundwater based on field and laboratory
data (Howard et al. 1991).
Using the average half-life values in Table 4-13 and assuming an initial concentration of
100 ug/L of total chlorinated VOCs, the time required for natural degradation to reduce individual
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chlorinated VOC concentrations below MCLs is approximately 5.33 years, which is equivalent to
1,945 days (see Table 4-14). The ratios of the individual chlorinated VOCs in the assumed initial
100-ug/L concentration (see Table 4-14) were based on the ratio of compounds present at the
Matthias Supply Well. If groundwater recovery systems are operated to capture and remove
chlorinated VOCs at or above 100 ug/L, the groundwater concentrations at 100 ug/L that are not
recovered will require approximately 5.33 years to naturally degrade below MCLs. This is a
conservative estimate because other factors (such as adsorption, dispersion, and dilution) will also
reduce groundwater concentrations. These calculations do not consider the potential variations of
concentrations due to the formation of breakdown products. Because PCE is not formed as a
breakdown product, the calculations for PCE represent a conservative estimate.
Chlorinated VOCs in the deeper portions or lateral portions of the aquifer not captured by
recovery wells should degrade below MCL concentrations within a maximum time frame of
approximately 5.33 years. Due to the existing groundwater flow regime, the deeper and lateral
portions of the main body of the chlorinated VOC plumes will not significantly expand over the
time required for natural degradation to achieve MCLs. However, the downgradient portion of the
existing chlorinated VOC plume in the southeastern part of the study area will continue to migrate
with the prevailing groundwater flow. To assess the additional area that may be potentially
impacted by chlorinated VOCs above MCLs, the downgradient extent of potential impact can be
estimated by calculating the groundwater flow velocity and multiplying this velocity by the time
required to reach MCLs.
The average linear velocity of groundwater flow is the velocity of groundwater moving in a
general downgradient direction. This velocity can be calculated using an equation derived from
Darcy's law as follows:
V 
= 
K dh
n dl
where V 
= Average linear velocity, in feet per day
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K 
= Hydraulic conductivity, in feet per day
n 
= Effective porosity (unitless)
dh = Hydraulic gradient (unitless)
dl
For the southeastern portion of the study area, the nearest values for K were calculated
from the pumping test at the Eglin HI Supply Well. Calculated K values for the Eglin in pumping
test ranged from 6.37 to 7.61 gal/day ft2; (Geraghty & Miller, Inc. 1995). Based on the distribution
of fractures interpreted from fracture trace analysis (Geraghty & Miller, Inc. 1995), the Harthman
Crusher Supply Well may be characterized by a density and length of fractures to similar to the
southeast portion of the study area. As such, the hydraulic conductivity (K) value calculated for
the Harthman Crusher Supply Well (21.1 gal/day ft2) may provide another applicable estimate for
the K values in the southeastern portion of the study area (Geraghty & Miller, Inc. 1995).
Conversion of the K values to units of feet per day yields a maximum K value of 1.02 feet per day
for the vicinity of the Eglin III Supply Well and 2.82 feet per day for the Harthman Crusher Supply
Well, with an average K value of 1.92 feet per day. Values of effective porosity for pyroclastic
rocks such as the andesitic tuff* found at the Tutu Wells Site may range from 14 to 40 percent
(Keller 1960). Using the average K value of 1.92 feet per day, a hydraulic gradient of 0.0689, and
an effective porosity of 0.20 (i.e., 20 percent), an average linear velocity of 0.661 foot per day
(ft/day) was calculated for the southeastern portion of the study area.
Multiplying 5.33 years (equivalent to 1,945 days, the estimated time required to achieve
MCLs using the average half-lives) by an average linear velocity of 0.661 ft/day (the larger
groundwater velocity calculated for the vicinity of the Matthias and Delegarde Supply Wells) yields
a value of 1,286 feet, which represents the maximum downgradient extent of migration of
chlorinated VOCs above MCLs from the 100-ug/L contour line in the vicinity of the Matthias
Supply Well. Chlorinated VOCs above the MCLs have been identified at the Delegarde Supply
Well, approximately 950 feet downgradient of the 100-ug/L chlorinated VOC contour line. The
minimum, average, and maximum input values for the half-life and travel time calculations are
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presented in Table 4-15. The average half-life and travel time calculations presented above indicate
that the southeastern edge of contaminants above MCLs may potentially migrate approximately
another 336 feet downgradient of the Delegarde Supply Well before natural degradation would
reduce the groundwater concentrations below MCLs. This is a very conservative estimate because
other retardation factors (e.g., adsorption and dilution with non-impacted groundwater) will also
limit the downgradient extent of chlorinated VOCs above MCLs. In addition, it is likely that the
hydraulic gradient will decrease, similar to the decrease in the topographic gradient, downgradient
of the Delegarde Supply Well. The Dench Supply Well, the nearest downgradient supply well, is
A
located approximately 2,200 feet downgradient of the Delegarde Supply Well. Sampling of the
Dench Supply Well over three sampling events (September 25,1990; February 5,1991; and March
31,1993) indicated that COCs were not present and that all results were below MCLs (Geraghty &
Miller, Inc. 1993c).
In summary, once the site-wide groundwater recovery is started, the main body of the
chlorinated VOC plume will be captured; this main body will no longer be a continuing source of
COCs to lateral and downgradient portions of the plume. Groundwater (with a maximum
concentration of 100 ug/L total' VOCs) not captured by the recovery wells should naturally
degrade to below MCLs within approximately 5 years. During this time, the southeast portion of
the plume may continue to migrate downgradient, but it will most likely degrade and dissipate
below MCLs before reaching the nearest downgradient groundwater supply well.
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5.4.8 Summary of Comparative Analysis of Alternatives
Table 5-13 provides a summary of the preferred remedial alternatives for each of the seven
NCP evaluation criteria. SRA 3 and SRA 4 are the soil remedies that have been designated most
often as the preferred alternative. SRA 3 (Institutional Controls/Capping/In-Situ SVE/Excavation
and Off-site Disposal) is the preferred soil remedial option for four of the seven criteria. SRA 4
(Institutional Controls/Capping/Ex-Situ SVE/Excavation and Off-site Disposal) is slightly better,
having been designated the preferred soil remedial option for five of the seven criteria. GRA 4
(Institutional Controls/Source and Plume Containment/Treatment/Discharge) is the most
commonly selected preferred groundwater remedy (four of the seven criteria).
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5. DEVELOPMENT AND SCREENING OF REMEDIAL ALTERNATIVES
In this section, screened technologies from Section 4.0 (Identification and Screening of
Remedial Technologies) are assembled into remedial alternatives to address the impacts to human
health and the environment that could result from COCs in soil and groundwater at the Tutu Wells
Site. Each remedial alternative is assessed based on the evaluation criteria provided in Section 5.1
(Evaluation Criteria) and on its effectiveness in achieving the goals and objectives established in
Section 3.0 (Remedial Action Croats and General Response Actions).
The RALs and CGs identified in Section 3.0 were utilized in formulating a basis for
compliance to the RAOs established for the site. As discussed in Section 3.1.2.3 (Remedial Action
Levels and Cleanup Goals), RALs do not exist at this time for soils. For the Tutu Wells Site, the
USEPA has developed SSLs to be used as screening levels to determine if soil remediation may be
warranted at individual properties.
5.1 EVALUATION CRITERIA
The evaluation criteria used to examine the remedial alternatives are derived from
CERCLA statutory requirements and other program initiatives, such as the NCP promulgated by
the USEPA. Each remedial alternative is evaluated against the NCP criteria as described in
"Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA-
Interim Final" (USEPA 1988a). The NCP criteria consist of the following nine factors, which each
remedial alternative must adequately address:
• 
Overall protection of human health and the environment.
• 
Compliance with ARARs.
• 
Long-term effectiveness and permanence.
• 
Reduction of toxicity, mobility, or volume.
• 
Short-term effectiveness.
• 
Implementability.
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• 
Cost.
• 
State acceptance.
• 
Community acceptance.
The first two criteria relate directly to statutory findings that must be made as part of a
Record of Decision (ROD). For this reason, they are categorized as threshold criteria with which
each remedial alternative must comply. The next five criteria are commonly referred to as the
primary balancing criteria. These five criteria make up the major portion of the comparative
analysis of remedial alternatives. The remaining two criteria, state and community acceptance, are
commonly referred to as modifying criteria. These criteria will be evaluated following completion
of the RI/FS and subsequent comment review. Table 5-1 presents a summary of the evaluation of
the NCP criteria for soil remedial alternatives. Table 5-2 presents a summary of the evaluation of
the NCP criteria for groundwater remedial alternatives.
5.2 DEVELOPMENT AND EVALUATION OF REMEDIAL ALTERNATIVES
FOR SOIL
In this section, soil remedial alternatives (SRAs) have been assembled and are evaluated
against seven of the nine factors set forth by the NCP. Each SRA must address these seven criteria
satisfactorily to be considered further as a potential remedy. Two criteria (state and community
acceptance) will be evaluated by the USEPA during and after the FS comment period. A summary
of the evaluation of the NCP criteria for SRAs is presented in Table 5-1.
In some cases, individual property owners have carried out site-specific investigations and
some of them are developing proposals for remedial action independent of this evaluation. These
proposals are considered separately in this FS Report, to assess the relationship of these proposals
with the site-wide remediation.
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Based on the available data, Geraghty & Miller has focused the evaluation of technologies
for soil treatment on the three presumptive remedies presented in USEPA guidance (USEPA
1993), which are SVE, thermal desorption, and incineration. Excavation of impacted soils is also
considered, combined with on-site treatment or off-site disposal. This alternative is provided for
those sites where volumes of impacted soil are small, such that treatment is not cost-effective.
Based on detailed evaluation of the three presumptive remedies, the published USEPA guidance
selects SVE as the primary presumptive remedy, followed by, in order of preference, thermal
desorption and incineration. SVE has been selected as the primary remedy to evaluate because the
remaining remedies were screened out in Section 4.0 (Identification and Screening of Remedial
Technologies) due to implementability aspects and cost difficulties.
The time frames needed for soil remediation at the various properties will be contingent on
the effectiveness of the SRA selected and the site-specific conditions. Based on experience with
similar site conditions (i.e., geology and COCs), in-situ SVE treatment systems usually attain CGs
approximately 2 to 5 years after start-up. Ex-situ SVE treatment systems can attain CGs within 1
or 2 years of start-up because the soil is more effectively treated in a more controlled environment.
Due to the potential presence of DNAPL in bedrock near the Curriculum Center and the O'Henry
Dry Cleaners, this FS Report assumes in-situ SVE will be applied for the entire remedial action,
which is assumed to be 30 years as specified in FS guidance (USEPA 1988a) for comparison of
alternatives.
Compliance with CGs will be determined through compliance monitoring sampling. For
in-situ and ex-situ soil treatment remedies, soil samples will be collected to determine if CGs have
been attained or if no further significant reduction of contaminant levels can be achieved. No
further remedial action would be required thereafter. Excavation and disposal would require
sampling during excavation to ensure the full extent of impacted soil has been removed.
Compliance monitoring of in-situ SVE systems in bedrock would have to be based on evaluations
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of the potential DNAPL present in the unsaturated bedrock areas. With further characterization of
the DNAPL areas, the in-situ SVE system influent concentrations should be reviewed periodically
to evaluate the point of diminishing returns. It is likely the influent concentrations will eventually
display an asymptote trend, at which point the further implementation of SVE will no longer
significantly reduce the contaminant levels, making it impractical to continue SVE treatment. If the
compliance monitoring for a remedial action indicates that significant reduction of the contaminant
levels has not been achieved, other remedial actions may need to be considered.
Based on the screening of technologies, Geraghty & Miller has focused the evaluation of
remedial technologies for soil and has assembled the following SRAs:
• 
SRA 1 : No Action/Institutional Controls.
• 
SRA 2: Institutional Controls/Capping.
• 
SRAS: Institutional Controls/Capping/In-Situ SVE (soil and bedrock)/Excavation and
Off-Site Disposal.
• 
SRA 4: Institutional Controls/Capping/Ex-Situ SVE/Excavation and On-Site Disposal.
• 
SRA 5: Institutional Controls/Capping/In-Situ SVE (bedrock)/Excavation and Off-Site
Disposal.
These SRAs are assembled using USEPA presumptive remedies and representative
technologies that survived screening in this FS Report. These SRAs are assembled in order from
generally the lowest level of action or disturbance of the site (SRA 1) to the highest level of action
or disturbance of the site (SRA 5). Each SRA has a particular technology that is the main theme or
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emphasis of the SRA (e.g., In-Situ SVE for SRA 3 and Ex-Situ SVE for SRA 4). However, the
technology emphasized by a particular SRA may not be effective or applicable due to site-specific
conditions at each property (e.g., shallow depth to bedrock or water table, proximity to building
foundations, type of potential exposure pathways). If a given technology was not considered
effective or applicable at a particular property, a more effective technology was used with the SRA.
As such, SRAs are composed of a mixture of technologies that are typically dominated by the
emphasized technology.
5.2.1 SRA 1; No Action/Institutional Controls
In this section, SRA 1 (No Action/Institutional Controls) is described and evaluated.
5.2.1.1 Description of SRA 1
This alternative, as proposed, would involve implementing deed restrictions. No treatment
or disposal actions would be taken for soil remediation. Existing remedial actions that are currently
in place for soil, if any, would remain in place (e.g., paving, concrete pads, or capping). In some
cases, individual property owners have carried out property-specific investigations and some of
them are developing proposals for remedial action independent of this evaluation. The remediation
proposals and plans resulting from these property-specific investigations are not considered part of
this alternative because proposed remedial actions currently considered by individual property
owners may not ultimately be implemented.
Institutional controls considered for the Tutu Wells Site would consist of deed restrictions
that restrict, regulate, or limit soil contact and excavation. Deed restrictions are assumed to be
necessary at properties that have been identified with contaminant concentrations in soil above the
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SSLs or USEPA acceptable risk values (CDM Federal Programs 1995a, 1995b). The properties
where deed restrictions might be applied are the Curriculum Center, Ramsay Motors, Texaco Tutu
Service Station, Tillett Gardens, Western Auto, Esso Tutu Service Station, and OHenry Dry
Cleaners. Such restrictions could consist of the following:
• 
Placing limitations on property usage (e.g., restricted to commercial or
industrial use).
• 
Prohibiting excavation or soil disturbance at any of the impacted areas without permit
approval, proper worker-protection precautions, and air monitoring for potential
fugitive emissions during excavation.
• 
Prohibiting the use or transport of excavated soil or rock from impacted areas.
• 
Prohibiting removal or disturbance of bedrock at properties where DNAPL may be
present (e.g., the Curriculum Center and OHenry Dry Cleaners).
5.2.1.2 Evaluation of SRA 1
Based on the results of the RI (Geraghry & Miller, Inc. 1995) and the Baseline Risk
Assessment (CDM Federal Programs Corporation 1995a), soil at some properties within the Tutu
Wells Site pose an unacceptable risk to human health and exceed the SSLs established for the Tutu
Wells Site. There are several properties, however, that have exceedances just above the SSLs.
Further risk analysis or continued natural biodegradation may indicate that soil remediation is not
necessary at these properties, making SRA 1 implementable. Confirmatory sampling and testing
should be done prior to implementation to ensure that other remediation is not warranted. Soil
exceedances of SSLs would be expected to continue to exist after implementation of this SRA, at
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least at some properties. Institutional controls may not be easily implementable and would involve
some administrative time to put into effect.
For the purposes of serving as a baseline for comparing remedial alternatives, and in
conformance with CERCLA guidance, the No Action/Institutional Controls alternative will be
retained for further consideration.
The estimated capital cost to implement SRA 1 is $15,000. The cost breakdown for the
activities that comprise SRA 1 is presented in Table 5-3.
5.2.2 SRA 2; Institutional Controls/Capping
This section presents a description and evaluation of SRA 2 (Institutional
Controls/Capping).
5.2.2.1 Description of SRA 2
This alternative would involve implementing the following actions:
• 
Implementation of deed restrictions at individual properties.
• 
Design and implement capping at all the properties where impacted soil and
where DNAPLs in bedrock are present.
This alternative limits access to contaminated areas through deed restrictions and eliminates
direct exposure to COCs through capping. Capping is proposed for each of the individual
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properties evaluated. This alternative would also significantly reduce the leaching of COCs to
groundwater. This is an important factor as the greatest potential impact to human health and the
environment from soil and potential DNAPLs in unsaturated bedrock at the Tutu Wells Site is
through leaching of COCs to groundwater.
Each individual property has been evaluated against the SSLs for the Tutu Wells Site. The
seven properties listed in Section 5.2.1.1 (Description of SRA 1) have been evaluated on an
individual property basis for SRA 2. Based on the property-specific circumstances, capping could
be installed, modified, and/or maintained at each property. Some individual properties are paved
and for all practical purposes are already capped. Other individual properties would require the
installation of a cap or pavement, where necessary. In addition to the restoration and maintenance
of the existing pavement at the Texaco Tutu Service Station and the Esso Tutu Service Station,
SCPs (that include in-situ SVE and/or bioventing) will be implemented at these properties. Where
DNAPLs are suspected in unsaturated bedrock, capping of the soils will be performed. At
OHenry Dry Cleaners, DNAPL impact in bedrock is suspected underneath the impacted soils. At
areas where DNAPL is suspected, capping is already provided by the building foundation.
5.2.2.2 Evaluation of SRA 2
This alternative is protective of human health and the environment when combined with
groundwater containment and treatment. Institutional controls may not be easily implementable
and would involve some administrative time to put into effect. Capping will prevent human and
animal contact with impacted soils, will reduce infiltration of water through the impacted soils, and
will reduce erosion. Capping will also reduce the leaching of contaminants from unsaturated
bedrock to groundwater.
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Capping and implementation of a soil erosion and sediment control plan at selected
properties will reduce erosion and the potential for exposure to hazardous materials. Capping will
also increase the quality of surface-water run-off.
Capping of the individual sites can be an effective method of reducing the transport of
VOCs. However, the technology will not reduce the level of VOCs in the soils or in unsaturated
bedrock. Exceedances of chemical-specific goals would be expected to continue. Action-specific
and location-specific ARARs are expected to be met through proper remedial design and
engineering, and through careful implementation.
Caps should be designed and constructed to reduce water and air infiltration through
contaminated soils and water infiltration through unsaturated bedrock. The reduction of water
infiltration will provide a long-term benefit by reducing the potential for migration of contaminants
from impacted soil into groundwater.
The toxicity and volume of contamination in impacted soil and unsaturated bedrock will
not be substantially reduced. The mobility of the COCs will be reduced by reducing the potential
for leaching of contaminants into the groundwater due to the reduction in infiltration. The amount
of residual contamination will not be reduced.
Moderate short-term impacts, such as fugitive emissions and erosion, may be associated
with installing the caps. Air monitoring can be performed to identify harmful emissions and
emissions that can be mitigated during cap installations. Dust control and emissions monitoring
and control measures implemented during construction will provide short-term protection of
human health and the environment.
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The implementation of SRA 2 is feasible and favorable. 
Geomembrane, pavement,
concrete, and soil caps are routinely installed using standard construction procedures and
equipment. Standard construction practices would be followed with the appropriate health and
safety protective measures.
SRA 2 is estimated to take approximately 12 to 18 months to implement. Costs for this
SRA would include administrative expenses related to implementing institutional controls and
engineering, material, and construction costs. The estimated capital cost to implement SRA 2 with
the SCPs is $338,000. The present-worth value of the estimated O&M costs for maintaining the
caps and the SCPs is $441,000. The total estimated cost for SRA 2 with the SCPs is $779,000.
The cost breakdown for the activities that comprise SRA 2 is presented in Table 5-4.
5.2.3 
SRA 3; Institutional Controls/Capping/In-Situ SVE (Soil and
Bedrocks/Excavation and Off-Site Disposal
This section presents a description and evaluation of SRA 3.
5.2.3.1 Description of SRA 3
This alternative would involve implementing the following actions:
• 
Implementation of deed restrictions limiting access to specified areas on
individual properties and future usage.
• 
Capping in areas where direct exposure to surface soil is considered a health
threat.
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• 
In-situ SVE, bioventing, or excavation and off-site disposal, depending on
property-specific conditions.
This alternative limits access to contaminated areas through deed restrictions, eliminates
direct exposure to COCs through capping, and provides SVE treatment at impacted areas. Each
individual property has been evaluated against the SSLs for the Tutu Wells Site. Some individual
properties are paved and for all practical purposes are capped, and will only require maintenance
and upkeep. Other individual properties would require the installation of a complete cap or
pavement system, where necessary.
The soil remediation for SRA 3 would consist of the actions listed at each of the following
sites, respectively:
Curriculum Center
• 
Excavation and disposal (in southeast U.S.) of impacted soil due to shallow
depth to bedrock and small soil volumes.
• 
In-situ SVE in unsaturated bedrock areas where DNAPL may be present above
the water table.
• 
Thermal oxidation for off-gas treatment.
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Ramsav Motors
• 
Capping of impacted soil. Existing maintenance garage floor slab is cracked
and is suspected to have released surface spills to the subsurface (Cooper
Environmental, Inc. 1993). Geraghty & Miller's cost estimate assumes the
concrete slab will be removed and replaced.
Texaco Tutu Service Station
• 
SVE for in-situ treatment of impacted soil.
• 
Catalytic oxidation for off-gas treatment (based on the SCP design; Erler &
Kalinowski, Inc. 1995a, 1995b).
Tillett Gardens
• 
Capping of impacted surface soil (to eliminate the exposure pathways).
Western Auto
Excavation and off-site disposal (in southeast U.S.) of impacted soils after
waste classification (for cost estimating purposes, Geraghty & Miller has
assumed the soil will be classified as a hazardous waste). SVE would not be
effective at Western Auto due to clayey soil.
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Esso Tutu Service Station
• 
In-situ SVE and bioventing in areas of impacted soil.
OHenry Dry Cleaners
• 
In-situ SVE for treatment of impacted soil.
• 
In-situ SVE in the unsaturated bedrock areas where DNAPLs may be present
above the water table.
• 
Thermal oxidation for off-gas treatment.
Based on the specific circumstances present at each individual property, SRA 3 could be
designed and installed. Reevaluating the necessity for remediation at each property should be
conducted during the pre-design phase to confirm that remediation is indeed warranted and to
document COC concentrations in soil prior to remedial action. Capping the areas where treatment
is to be installed may also be made part of the design to limit direct exposure to the impacted soil;
impermeable liners may also prevent "short circuiting" of SVE treatment that may occur in shallow
soil areas. In most cases, SRA 3 would consist of the installation of SVE wells, a blower, and an
off-gas treatment system, and excavation and off-site disposal of soil as a hazardous waste.
5.2.3.2 Evaluation of SRA 3
Based on the results of the RI (Geraghty & Miller, Inc. 1995), soil quality at several
properties in the Tutu Wells Site area may represent the potential to leach COCs to groundwater,
posing an unacceptable risk to human health and the environment. Implementation of institutional
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controls combined with SVE treatment and, potentially capping, can effectively mitigate the
potential exposure pathways for COCs in soil and meet the NCP requirements for protection of
human health and the environment.
Institutional controls may not be easily implementable and would involve some
administrative time to implement. However, institutional controls can be effective in regulating
unauthorized soil excavation or property use.
Impermeable covers, where implemented, will reduce the infiltration of water through
impacted soil, which will reduce the potential for leaching of COCs into the groundwater.
Impermeable covers will also prevent human and animal contact with contaminated soil and reduce
erosion. Implementation of soil erosion and sediment control at selected properties will reduce
erosion and the potential for exposure to hazardous materials. Impermeable covers will also
increase the quality of surface-water run-off.
SVE will reduce the level of contaminants in soil at the specified properties, thus reducing
the potential for leaching of contaminants to groundwater and subsequent off-site migration. Air
emission controls on the SVE system will be protective of human health and the environment by
meeting emission permit standards.
This SRA would be designed to meet the CGs for the site. Exceedances of chemical-
specific goals may persist depending on the level of contamination that can be extracted at each
individual property. Sites where capping is implemented will continue to exceed the chemical-
specific goals. Action-specific and location-specific ARARs are expected to be met through proper
remedial design and engineering, and through careful implementation.
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SVE and/or bioventing is expected to be an effective method of reducing the
concentrations of COCs. Further effectiveness may be achieved by installing a cap that would be
designed and constructed to reduce water and air infiltration during operation of the SVE system.
The reduction of water infiltration will provide a long-term benefit by reducing the potential for
migration of contaminants from impacted soil into groundwater.
This SRA reduces the toxicity, mobility, and volume of soil contamination at individual
properties through treatment. The potential for leaching of contaminants into the groundwater will
be reduced since the potential source areas will be treated and/or capped. The amount of residual
contamination at each site will depend on the effectiveness of the remediation.
Moderate short-term impacts would be realized due to fugitive emissions and the potential
erosion associated with installing caps, SVE wells, and/or excavation. Dust control and emissions
monitoring and control measures implemented during construction will provide short-term
protection of human health and the environment. Air monitoring will be performed to identify
harmful emissions during installation.
SRA 3 is implementable. In-situ SVE and bioventing are technically and administratively
implementable, and have been demonstrated to be effective in treating the COCs identified at the
Tutu Wells Site. SVE is effective at treating chlorinated VOCs and BTEX. Bioventing can be
applied where BTEX treatment is the primary objective. However, the time required to remediate
the impacted area will be longer than if more dynamic treatment using in-situ SVE is applied.
Additional pilot testing will be required to refine engineering design parameters and operating
conditions. Where SVE is to be used to treat potential DNAPLs in unsaturated bedrock, extensive
site characterization to confirm the presence and extent of DNAPLs in the unsaturated zone should
be performed with care, to minimize the further mobilization of the potential DNAPL in the
subsurface.
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Construction of the cap and SVE system is not expected to involve any significant
implementability problems. 
Geomembrane, pavement, concrete, and soil caps are routinely
installed using standard construction procedures and equipment. Standard construction practices
will be followed with the appropriate health and safety protective measures.
Capital costs associated with SRA 3 would include administrative and engineering costs
related to permitting and engineering design; potential air modeling; pilot testing; and material and
construction costs. O&M costs would involve costs related to the O&M of vapory-phase treatment
unit(s) and the costs of inspecting and maintaining the soil caps. Additional soil investigation may
be required at some individual properties to verify that remediation is indeed warranted and to
document soil concentrations prior to remedial actions.
The estimated capital cost to implement SRA 3 with the SCPs is $1,561,000. The
present-worth value of the estimated O&M costs for maintaining the caps and the SVE/SCP
systems is $2,553,000. The total estimated cost for SRA 3 with SCPs is $4,114,000. The cost
breakdown for the activities that comprise SRA 2 is presented in Table 5-5.
5.2.4 SRA 4; Institutional Controls/Capping/Ex-Situ SVE/Excavation and On-Site
Disposal
This alternative proposes the implementation of institutional controls and excavation of
impacted soil at identified properties, and ex-situ SVE treatment for soil remediation. Soil would
be treated to CGs and replaced in the excavated area. In-situ SVE systems would be installed in
fractured bedrock where DNAPLs potentially exist in the unsaturated zone (i.e., the Curriculum
Center and OHenry Dry Cleaners). Impacted soil beneath existing buildings may not be suitable
for excavation due to potential impacts to nearby structures and foundations. Capping or in-situ
SVE would be more suitable at these locations.
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5.2.4.1 Description of SRA 4
This alternative would involve implementing the following actions:
• 
Implementation of deed restrictions limiting access to specified areas at
individual properties and future site usage.
• 
Installation of a treatment system, consisting of ex-situ SVE or biopiles, and a
off-gas treatment system.
• 
Capping in areas where any of the following conditions exist:
- 
Direct exposure to surface soil is considered a health threat.
- 
Existing buildings may limit feasibility and cost-effectiveness of
excavation for ex-situ treatment.
Deed restrictions, where applicable, would be implemented to restrict site access and future
usage. In most cases, SRA 4 would consist of the installation of SVE wells, a blower, and an off-
gas treatment system. For the proposes of this FS Report, the use of thermal or catalytic oxidation
will be assumed for off-gas treatment. Capping the areas where treatment is to be installed may
also be made part of the design to limit direct exposure to the impacted soil and to prevent short
circuiting of in-situ SVE systems.
In summary, the soil remediation for SRA 4 would consist of the actions listed below for
each of the following sites, respectively:
,#«»"««"X
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Curriculum Center
• 
Excavation, ex-situ SVE, and replacement of remediated soil.
• 
In-situ SVE in bedrock or in soil areas not suitable for excavation (i.e., near
building foundations) to remediate adsorbed chlorinated VOCs or DNAPLs
that may be present in the unsaturated zone.
Ramsay Motors
• 
Capping by replacement of cracked concrete.
Texaco Tutu Service Station
• 
In-situ SVE and/or bioventing treatment of impacted soils.
• 
Catalytic oxidation for off-gas treatment (based on the SCP design; Erler &
Kalinowski, Inc. 1995a, 1995b).
Tillett Gardens
• 
Capping of impacted soil areas (to eliminate the exposure pathways).
Western Auto
• 
Excavation and off-site disposal (in southeast U.S.) of impacted soil after waste
classification (for cost estimating purposes, Geraghty & Miller has assumed the
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soil will be classified as hazardous waste). SVE would not be effective at
Western Auto due to clayey soil.
Esso Tutu Service Station
In-situ SVE and/or bioventing treatment of impacted soil.
OHenrv Dry Cleaners
• 
Excavation, ex-situ treatment of impacted soils, and replacement of remediated
soil.
• 
In-situ SVE in bedrock or in soil areas not suitable for excavation (i.e., near
building foundations) to remediate DNAPL that may be present in the
unsaturated zone.
5.2.4.2 Evaluation of SRA 4
Soil quality at several properties in the Tutu Wells Site area may pose an unacceptable risk
to human health and the environment. Implementation of institutional controls combined with
treatment and/or capping, where required, can effectively mitigate the potential exposure pathways
present for soil.
Capping will reduce the infiltration of water through contaminated soil, which will reduce
the potential for leaching of COCs into groundwater. These measures will also prevent human and
animal contact with contaminated soil and reduce erosion.
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SVE will reduce the level of contaminants in soil at the specified properties, thus reducing
the potential for leaching of contaminants to groundwater and subsequent off-site migration. Air
emission controls on the SVE systems and covering of the soil piles (if using ex-situ SVE
treatment) will be protective of human health and the environment by meeting emission permit
standards.
Capping and implementation of soil erosion and sediment control at selected properties will
reduce erosion and the potential for exposure to hazardous materials. Capping will also increase
the quality of surface-water run-off. Dust control and emissions monitoring and control measures
implemented during construction will provide short-term protection of human health and the
environment.
This SRA would be designed to meet the CGs for the site. Exceedances of chemical-
specific goals may occur depending upon the level of contamination that can be extracted through
ex-situ SVE treatment. Action-specific and location-specific ARARs can be met through proper
remedial design and engineering, and through careful implementation. At properties where capping
is implemented, chemical-specific ARARs are expected to continue to be exceeded.
This SRA would reduce the toxicity, mobility, and volume of soil contamination at
individual properties through treatment. 
The potential for leaching of contaminants into
groundwater will be reduced since the source will be treated, reducing the source volume. If
required, the impacted soil will be capped, reducing mobility. 
The amount of residual
contamination at each site will depend on the effectiveness of each excavation and treatment
system. The effectiveness may also be limited by the amount of soil that can be excavated due to
potential structural concerns near building foundations.
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Moderate short-term impacts would be realized due to fugitive emissions and the potential
erosion associated with installing caps, excavation of soil, and installation of SVE equipment. Air
monitoring may be required to identify harmful emissions during installation. Dust control and
emissions monitoring and control measures implemented during construction will provide short-
term protection of human health and the environment. Standard health and safety precautions
would be maintained to mitigate any risks from drilling extraction wells in waste areas.
This SRA is implementable. SVE is technically and administratively implementable, and
has been demonstrated to be effective in treating the COCs identified at the Tutu Wells Site.
Additional pilot work may be required to refine engineering design parameters and operating
conditions. 
Construction of caps and SVE systems should not involve any significant
implementability problems. 
Geomembrane, pavement, concrete, and soil caps are routinely
installed using standard construction procedures and equipment. Standard construction practices
will be followed with the appropriate health and safety protective measures.
Capital costs associated with SRA 4 would include administrative and engineering costs
related to permitting and engineering design, and possible air modeling and pilot testing, and
material and construction costs. O&M costs would involve costs related to the O&M of vapor
phase treatment unit(s). Additional soil evaluations at some individual properties may also be
required to verify that remediation is warranted.
The estimated capital cost to implement SRA 4 with the SCPs is $1,530,000. The present-
worth value of the estimated O&M for SRA 4 with the SCPs is $2,524,000. The total estimated
cost for SRA 4 with the SCPs is $4,054,000. The cost breakdown for the activities that comprise
SRA 4 is presented in Table 5-6.
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5.2.5 SRA 5: Institutional Controls/Capping/In-Situ SVE (BedrockVExcavation and
Off-Site Disposal
In this section, SRA 5 is described and evaluated against the NCP criteria.
5.2.5.1 Description of SRA 5
This alternative would involve implementing the following actions:
• 
Implementation of institutional controls.
• 
Excavation and off-site disposal of impacted soil at individual properties
identified.
• 
Implementation of the SCPs using in-situ SVE at the Texaco and Esso
properties.
• 
Capping selected areas where impacted soil is present.
• 
In-situ SVE treatment in bedrock at the Curriculum Center and the OHenry
Dry Cleaners.
• 
Restoration of excavated areas.
Soil at individual properties where contamination is above the SSLs identified for the Tutu
Wells Site would be excavated and containerized as required. The exceptions to this would be
Tillett and Ramsay Motors where capping would be implemented, and the Texaco and Esso
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properties where the SCPs would be implemented. The excavated soil would be containerized and
sampled to determine if it should be classified as hazardous waste. Based on that sampling, the soil
would be disposed as appropriate and as approved by the USEPA and the appropriate U.S. Virgin
Island agencies. Geraghty & Miller has assumed, for the purposes of this FS Report, that all
excavated soil will be disposed as hazardous waste. Fill material would be brought in to restore
each of the areas to grade. Topsoil and seed or paving would be installed to finish the restoration.
After restoration is complete, deed restrictions (if necessary) would be placed on the
property restricting current and future use. During all phases of the remediation, it will be
necessary to implement dust and volatile emission control measures, soil erosion, and sediment
control measures.
5.2.5.2 Evaluation of SRA 5
This alternative would protect human health and the environment by effectively removing
the source of contamination from individual properties or by effectively eliminating the risk of
exposure by leaching of COCs to groundwater through capping.
This alternative would require air monitoring, use of personal protective equipment, and
engineering controls for the control of fugitive emissions during the excavation and handling of
waste materials to provide short-term protection of human health.
This alternative is expected to meet potential CGs for the Tutu Wells Site by placing the
material in a permitted off-site landfill. Soil that is classified as hazardous would have to be shipped
to a hazardous waste landfill outside the USVI (a site in the southeast U.S. is assumed for cost
purposes). 
By removing the contaminated soil, the potential for leaching of COCs into
groundwater would be eliminated.
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Location-specific and action-specific ARARs are expected to be met through proper
remedial design and implementation. Chemical-specific ARARs could be met through in-situ SVE
treatment and ex-situ off-site disposal. The only exceptions would be for the Ramsay and Tillett
properties where capping will eliminate the exposure pathway, but capping will not reduce the
contaminant concentration.
Contaminated soil removal and off-site disposal represents a permanent remedial solution
for soil contamination at the Tutu Wells Site. The remediated area would be backfilled with clean
fill and graded to restore existing grade. Erosion control measures would be implemented.
Off-site disposal and replacement with clean fill will reduce the toxicity, mobility, and
volume of the impacted soil in the Tutu Wells Site area. Source removal will decrease the potential
for leaching of COCs into groundwater. The volume of contamination in the soil medium will be
significantly reduced on-site, and the effectiveness of the removal of the soil would be contingent
upon the ability to completely remove the impacted soil.
Due to the proximity of private residences and a business district in the vicinity of the Tutu
Wells Site, there are more potential short-term impacts associated with this alternative than with
the other SRAs. The volatile nature of some of the COCs present at the Tutu Wells Site could
result in the release of harmful emissions during excavation, handling, and transport. Measures
such as temporary enclosures and daily cover may be needed to contain these emissions. Air
treatment would be needed for these enclosures and air monitoring would be required to monitor
for off-site migration of fugitive emissions. Specific health and safety practices for the selected
properties can be developed to control exposure to on-site workers and personnel, as well as to
potential off-site receptors.
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Excavation of contaminated soil and transfer to an off-site landfill is expected to be difficult
to implement. The depth and location of some excavations may require the installation of lateral
support members (e.g., sheet piles), and/or underpinning of building foundations. Excavation may
not be implementable for impacted soil areas beneath footings. Bedrock that may be impacted
could not be excavated. Transportation of hazardous materials on local roads will be difficult, as
will the transportation of impacted soil by barge. The logistics of transporting the material from the
site to the off-island landfill must be tightly controlled and will be administratively difficult to
implement. Capped areas will be significantly easier to implement as a remedy.
Capital costs for SRA 5 would consist of administrative and engineering costs, and costs
related to excavation, transport, disposal, and monitoring. O&M costs would be minimal and
would be limited to the areas that are capped.
The estimated capital cost to implement SRA 5 with the SCPs is $2,065,000. No O&M
costs will be incurred after excavation and disposal is completed. However, the O&M required to
maintain the caps at the Ramsay and Tillett properties, the in-situ SVE in bedrock at the
Curriculum Center and the O'Henry Dry Cleaners and the SCPs has an estimated present-worth
value of approximately $2,460,000. The estimated grand total for SRA 5 and the SCPs is
$4,525,000. The cost breakdown for the activities that comprise SRA 5 is presented in Table 5-7.
5.3 
DEVELOPMENT AND EVALUATION OF REMEDIAL ALTERNATIVES
FOR GROUNDWATER
In general, the proposed groundwater remedies are pump and treat scenarios. Past
experience with sites where DNAPLs have been identified indicates that portions of the fractured
bedrock may never be fully restored. Therefore, it is assumed that each GRA will continue to
operate for the entire remedial action. For the purposes of cost comparison, FS guidance (USEPA
1988a) recommends the use of 30 years for the duration of remedial actions. At some point in time
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•/—V
during the life cycle of the remedial action, groundwater recovery and treatment may no longer
assist in the reduction of contaminants levels to CGs (i.e., MCLs). Once this asymptotic level is
reached, the groundwater remedial action will no longer be able to significantly reduce the COCs in
groundwater.
Every five years during the life cycle of a remedial action (or more frequently, as needed), a
performance review of the remedial system should be performed to determine if portions of the
aquifer have obtained MCLs. The results of the semi-annual compliance monitoring samples will
provide data for these remedial system performance reviews. If VOC concentrations in portions of
the aquifer are reduced below MCL concentrations, the possible use of groundwater for beneficial
uses may be allowed in specified areas.
Four remedial alternatives have been developed to address impacted groundwater on a site-
wide basis. The four groundwater remedial alternatives (GRAs) assembled for comparison are the
following:
• 
GRA 1: No Action/Institutional Controls.
• 
GRA 2: Institutional Controls/Source Containment/
POET Systems/Treatment/Discharge.
• 
GRA 3: Institutional Controls/Plume Containment/Treatment/Discharge.
• 
GRA 4: Institutional Controls/Source and Plume Containment/Treatment/Discharge.
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5.3.1 GRA 1; No Action/Institutional Controls
In this section, GRA 1: No Action/Institutional Controls is described and evaluated.
5.3.1.1 Description of GRA 1
This remedial alternative would involve implementing deed restrictions and monitoring.
Deed restrictions on groundwater use may include the following:
• 
Requiring the decommissioning of domestic and commercial wells. 
Existing
unpermitted supply wells can be decommissioned by removing the pump and placing a
removable plug in the well. The wells can be reestablished at some point in the future,
when and if groundwater quality improves to allow extraction and use of untreated
groundwater.
• 
Prohibiting unauthorized usage of groundwater or the installation of new wells.
• 
Placing restrictions on the water supply sources for future residential growth.
• 
Limiting water system installations to connection to the Water and Power Authority
(WAPA) distribution system or an alternate authorized source.
GRA 1 includes semi-annual groundwater sampling to monitor groundwater quality and
contaminant migration. 
For purposes of comparison, the monitoring program includes the
sampling of approximately 15 wells at or near the plume boundary for TCL VOCs and BNAs, and
the monitoring program will be assumed to last throughout the remedial action (30 years).
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Restrictions on groundwater use would be established to prevent the installation of new
supply wells in the affected area. To prevent future use of the existing wells, all existing supply
wells at the Tutu Wells Site would be decommissioned. The DPNR would be responsible for
enforcing restrictions on groundwater use and for ensuring that no unpermitted groundwater
pumpage occurs. Water would continue to be supplied as it is currently being supplied (i.e.,
through collection of rain water and trucking water from an alternate source).
,—N
5.3.1.2 Evaluation of GRA 1
Based on the results of the RI (Geraghty & Miller, Inc. 1995) and the Baseline Risk
Assessment (CDM Federal Programs Corporation 1995a), the groundwater under the site
currently poses and will continue to pose an unacceptable risk to human health by ingestion.
Implementation of institutional actions will not control the migration of impacted groundwater.
This alternative would guard against potential impacts to human health within the Tutu Wells Site
area, but may not protect human health off-site since plume migration would not be controlled.
Institutional controls may not completely prevent unauthorized use of groundwater, unauthorized
use of groundwater could still occur. Currently, there have not been any documented impacts to
ecological receptors resulting from exposure to impacted groundwater, and the RI indicated such
impacts are not likely (Geraghty & Miller, Inc. 1995). Potential impacts to ecological receptors are
not discussed in the Baseline Risk Assessment.
This alternative would not be in compliance with chemical-specific ARARs. Exceedances
of these ARARs would be expected to continue. The long-term effectiveness of this alternative is
questionable. Groundwater transport of contaminants would continue, and risks from direct
contact and other pathways, although reduced, would not be eliminated. No appreciable reduction
in toxicity, mobility, or volume of the contaminants at the Tutu Wells Site would result from
implementation of this alternative.
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Short-term effectiveness is favorable as there would be little or no short-term impacts
associated with implementation of GRA 1. 
Minimal short-term impacts, relating to
decommissioning of the existing wells in the area, can be assumed. Personal protective equipment
for workers would control exposure during implementation, if warranted. The time to implement
this alternative would be approximately 12 months from the date all required approvals were
obtained.
Institutional controls may not be easily implementable and would involve considerable
administrative time. The DPNR would be responsible for preventing unauthorized groundwater
pumpage.
The total cost for this alternative would be a combination of administrative costs associated
with securing deed restrictions, the construction costs related to abandonment of the existing wells,
and the commercial costs related to monitoring and laboratory testing.
The estimated capital cost to implement GRA 1 is $15,000. The estimated present-worth
value of the estimated cost to conduct groundwater monitoring over 30 years is $1,757,000. The
total estimated cost is $1,772,000. The cost estimates presented do not include a cost for
devaluation of property due to deed restrictions. The cost breakdown for the activities that
comprise GRA 1 is presented in Table 5-8.
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5.3.2 
GRA 2: Institutional Controls/Source Containment/POET
Svstems/Treatment/Discharge
This section describes GRA 2 and summarizes the evaluation based on the criteria
established by the NCP.
5.3.2.1 Description of GRA 2
This remedial alternative involves implementing the following:
• 
Implementation of deed restrictions related to future site usage and water
supply well installation.
• 
Installation of groundwater recovery wells for hydraulic control of contaminant
sources.
• 
Long-term monitoring of groundwater.
• 
Installation of POET systems at selected existing supply wells.
• 
Installation of a central treatment facility.
• 
Discharge of treated groundwater to surface water via the storm sewer near the
OHenry Dry Cleaners (see Figure 5-1).
• 
Natural attenuation of the dissolved chlorinated VOC plume downgradient of
the Smith and Matthias Supply Wells.
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This remedial alternative proposes a methodology for hydraulic containment of the
potential groundwater contamination source areas that exhibit the highest groundwater VOC
concentrations, and incorporates ex-situ treatment of groundwater and discharge of the treated
groundwater to surface water.
The groundwater remediation proposed for GRA 2 consists of containing high-
concentration portions of the existing chlorinated VOC plumes by providing source containment at
the potential sources of groundwater contamination (i.e., the Curriculum Center area and the area
proximate to OHenry Dry Cleaners) and allow selected private wells to pump utilizing POETs for
treatment. The currently proposed SCPs at the Texaco Tutu Service Station and the Esso Tutu
Service Station will provide source containment where BTEX constituents are the primary COCs.
The source containment would provide hydraulic barriers around source areas, thus reducing
COCs in other parts of the aquifer and potentially reducing the time to reach CGs in large portions
of the Tutu Wells Site. The recovery well scheme that would be implemented in GRA 2 involves
the use of the Source Recovery Wells pumping scenario described in Section 4.6.3.1 (Collection
and Containment) (see capture zones for Recovery Wells RW-4 and RW-5 in Figure 4-10, with
pumpage of selected private domestic and commercial wells). Pilot studies may be required to
evaluate the most effective technologies for treatment.
Pumpage for commercial potable supply would not be permitted. Selected wells equipped
with POET systems would be allowed to pump for private use or for sale for non-potable uses. For
the purposes of this FS Report, the supply wells assumed to have POET systems include the Four
Winds I, Steele, LaPlace, Matthias, and Smith Supply Wells (see Table 4-12). These wells were
selected because they are located in the center of the chlorinated VOC plumes and could therefore
provide containment and removal of contaminants. This selection of supply wells for pumpage is
preliminary; the final selection will be made by the USEPA and the DPNR if GRA 2 is selected.
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The remaining wells would be decommissioned and/or sealed. The Four Winds I Supply Well
could pump at an average rate of 10 gpm; the remaining four wells would be allowed to pump at
an average rate of 1.25 gpm each, equivalent to normal residential usage rates for each well. The
total average pumping rate allowed in GRA 2 for supply wells is approximately 1 5 gpm.
Effluent quality will be specified by the requirements of the permit to discharge to surface
water. The treatment scheme that would be employed is illustrated on Figure 4-11. Figure 5-1
illustrates the conceptual layout for this GRA The total flow capacity of the treatment facility
would be 55 gpm.
A number of residential and commercial wells within the Tutu Wells Site would have to be
decommissioned. Residential groundwater use in some areas could interfere with the hydraulic
containment program and reduce the program's effectiveness in containing the impacted
groundwater.
In areas of the aquifer where groundwater is not anticipated to create adverse impacts to
human health (i.e., in the area beyond the Delegarde Well and the deeper portions of the aquifer),
natural attenuation is proposed. Active remediation of these portions of the aquifer will not
decrease the time required to remediate the site and would increase remediation costs substantially.
5.3.2.2 Evaluation of GRA 2
This remedial alternative includes POET systems (which the USEPA does not consider to
be an adequate long-term solution for the potential impact on human health) that are unfavorable
for protection of human health. The USEPA considers POET systems to pose potential risks to
consumers due to potential equipment malfunctions. The effectiveness of controlling off-site
migration is contingent upon developing an effective containment program.
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This alternative has the potential for compliance with anticipated ARARs related to
groundwater. Potential chemical-specific ARARs for discharge can be met through ex-situ
treatment, and site constituent migration will be reduced by the proposed pumping of residential
wells. Natural attenuation can, in time, allow portions of the aquifer to meet the potential
chemical-specific ARARs for groundwater. The effectiveness of natural attenuation will be
contingent on the effective capture of the residential well pumping. Geraghty & Miller anticipates
that complete capture will not be accomplished through implementation of a residential well
pumping program; therefore, GRA 2 may not protect human health off-site.
The remedial alternative is essentially a pump and treat system, which is a proven long-term
and permanent groundwater containment remedy at many CERCLA sites. The containment
program has the potential to prevent some, but not all, off-site contaminant migration. Geraghty &
Miller anticipates that source containment would result in an eventual decrease in constituent
concentrations site-wide and would also guard against drawing groundwater contaminants with
higher VOC concentrations toward groundwater with lower VOC concentrations, thereby
minimizing contaminant migration.
The use of POET systems with institutional controls may not be effective as a long-term or
permanent remedy. The potential for off-site groundwater transport of contaminants may still
exist, depending on the ability to utilize private wells and to coordinate their pumpage to
hydraulically contain impacted groundwater. These factors suggest that long-term effectiveness
and permanence may be limited. The reduction of toxicity, mobility, and volume would be
moderate because effective source control would maximize constituent removal from groundwater,
and intermittent pumping of residential wells equipped with POETs would also result in some
reduction in the volume of COCs in groundwater.
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Short-term effectiveness is moderately favorable; there would be minimal impacts related
to implementation of recovery wells, POET systems, and a central treatment facility. The time to
implement institutional controls and execute well abandonment would be moderate; however,
additional time may be required for start-up of the recovery program and treatment system.
Installation of POETs may be difficult to implement due to potential problems with installation on
individual properties. Property would have to be secured for construction of the treatment
systems, and access agreements for recovery wells would be required. A permit for discharge to
surface water would be required, and time to construct a treatment system would be required.
Personal protective equipment for workers would be used to control exposure during
implementation, if needed.
Administrative implementability may be difficult. Wells are owned by individual property
owners, which may create a need for a significant amount of coordination to implement. It may be
difficult to ensure that the unpermitted wells are not pumped and that the safe yield of the aquifer is
not exceeded. Operation issues could be significant due to maintenance related to a treatment
facility and the operation of individual property owner POET systems. The reliability of POET
system technologies has proven satisfactory when used as an interim measure. Monitoring of the
POET systems would involve periodic O&M requirements throughout the life of the remedial
action, and the risk of exposure would be high if monitoring requirements were insufficient to
detect system failures. Implementation time is estimated to be approximately 12 to 18 months
from the date approvals for installation are obtained.
The costs to implement this remedial alternative would consist of the administrative cost
and the engineering, material, and installation costs of the collection, treatment, and discharge
systems. There would also be O&M costs associated with operating the collection/treatment
system, monitoring of the plume, and providing O&M for the POET systems. The estimated
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capital cost to implement GRA 2 with the SCPs is $2,366,000 with an estimated total O&M
present-worth cost of $7,793,000 and an estimated grand total of $10,159,000 (see Table 5-9).
5.3.3 GRA 3: Institutional Controls/Plume Containment/Treatment/Discharge
This section describes and evaluates GRA 3, using the criteria established by the NCP.
5.3.3.1 Description of GRA 3
The following actions would be implemented:
• 
Implementation of deed restrictions related to further site groundwater use.
• 
Decommissioning of residential and commercial wells.
• 
Installation of groundwater recovery wells for hydraulic control of plume
migration.
• 
Construction of a central groundwater treatment facility.
• 
Discharge of treated groundwater to surface water.
• 
Natural attenuation of dissolved plume downgradient of Recovery Wells RW-2
and RW-3, and below an approximate depth of 150 feet bis.
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This remedial alternative proposes a methodology for hydraulic containment of the
delineated plumes and incorporates ex-sttu treatment of groundwater and discharge of the treated
groundwater to surface water.
The proposed containment program would include the installation of Recovery Wells
RW-1, RW-2, and RW-3 strategically placed to hydraulically contain plume migration (see Figure
4-10). Existing supply wells would be decommissioned to avoid influencing the containment
program and to control unauthorized exposure to groundwater impacted by site constituents.
Potable water would continue to be supplied as it is now. The containment program would be as
described in Section 4.6.3.1 (Collection and Containment).
Recovered groundwater would be collected and conveyed to a central treatment facility.
Treatment of the groundwater for surface-water discharge would be accomplished using a
treatment facility similar to the facility illustrated on Figure 4-11. The total flow capacity of the
treatment facility would be 45 gpm.
A number of residential and commercial wells within the Tutu Wells Site would have to be
decommissioned. Residential and commercial groundwater use in some areas would counteract
the hydraulic containment program and reduce the program's effectiveness in containing the
impacted groundwater.
Property acquisition would be required for the central treatment facility. Sufficient room
would be needed to construct the facility and meet local ordinance set-back requirements. A site
located in the vicinity of the southern plume containment wells is assumed. Such a location would
be at a lower elevation when compared to the rest of the Tutu Wells Site, thus reducing pumping
requirements.
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Natural attenuation is proposed for the portions of the plume where groundwater impacts
exist southeast of Recovery Wells RW-2 and RW-3, and for groundwater below a depth of
approximately 150 feet bis.
The implementation of institutional controls could initially be as extensive as those
proposed in GRA 1, but could be reduced later in the remedial action depending on the
effectiveness of the GRA in meeting CGs. Unauthorized groundwater pumpage will have to be
effectively controlled throughout the remedial action. A monitoring program of the same scope as
proposed in GRA 1 would also be required with GRA 3.
5.3.3.2 Evaluation of GRA 3
This remedial alternative can adequately address the impact that the Tutu Wells Site will
have on human health. Although the potential for unauthorized use of groundwater would still
exist, implementation of institutional controls with a containment program would effectively
eliminate the potential exposure pathways by which groundwater would present a health risk. With
monitoring and adjustment, an effective containment program can be developed that would control
off-site migration, thereby reducing the potential for off-site human health impacts. The portions of
the plume where natural attenuation is proposed will be naturally remediated over time. Natural
attenuation will effectively reduce COCs below concentrations that could cause impacts to human
health or the environment.
This alternative has the potential for compliance with anticipated ARARs related to
groundwater. Potential chemical-specific ARARs for discharge can be met through ex-situ
groundwater treatment. Site constituent migration will be reduced by plume containment. The
effectiveness of natural attenuation in meeting chemical-specific ARARs downgradient of
Recovery Wells RW-2 and RW-3 will be contingent on the effectiveness of plume capture.
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Location-specific and action-specific ARARs will be met with through engineering controls and
proper implementation. Since there may be sources that would continue to be active under this
scenario, h is likely that portions of the aquifer will never meet the MCLs for groundwater without
treatment.
The toxicity, mobility, and volume of impacted groundwater would be reduced through
containment and pumping; however, the potential presence of DNAPL in the bedrock aquifer at
the Tutu Wells Site could act as a continual source of groundwater contamination throughout the
life of the remedial action.
Short-term effectiveness is moderately favorable; there would be impacts related to
implementation of the recovery wells and a central treatment facility. In addition, GRA 3 is not an
optimal collection system because COCs will migrate from the source areas through the aquifer to
the plume containment recovery wells. The time to implement institutional controls and execute
well decommissioning would be moderate; however, the time required for start-up of the recovery
program and treatment system is estimated to be approximately 12 to 18 months. Property would
have to be secured for construction of the central treatment facility and access agreements for
recovery wells would be required. Personal protective equipment for workers would be used to
control exposure during implementation.
The implementability of this alternative would be more similar to other options. A permit
would be required for surface-water discharge of treated water. Unauthorized groundwater
pumpage that would interfere with the effectiveness of this remedial system would need to be
enforced. Approvals for discharge could take as long as 12 to 18 months to secure.
The costs to implement this remedial alternative would consist of administrative cost and
the engineering, material, and installation costs of the collection, treatment, and discharge systems.
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There would also be O&M costs associated with operating the collection/treatment system and
monitoring of groundwater quality and the rate of attenuation.
The capital cost to implement GRA 3 with the SCPs is approximately $2,357,000. The
estimated total O&M present-worth cost estimated for GRA 3 and the SCPs is $6,143,000. The
estimated grand total cost is $8,680,000 (see Table 5-10).
5.3.4 
GRA 4; Institutional Controls/Source and Plume Containment/Treatment/
Discharge
This section presents a description and evaluation of GRA 4, using the criteria established
bytheNCP.
5.3.4.1 Description of GRA 4
The following actions would be implemented:
• 
Implementation of deed restrictions related to further site groundwater usage.
• 
Decommissioning of residential and commercial wells.
• 
Installation of groundwater recovery wells for hydraulic control of plume
migration.
• 
Installation of groundwater recovery wells for hydraulic control of areas
identified as potential source areas.
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• 
Construction of a central groundwater treatment facility.
• 
Discharge of treated groundwater to surface water.
• 
Natural attenuation of dissolved plume downgradient of Recovery Wells RW-2
and RW-3, and below an approximate depth of 150 feet bis.
This action proposes the containment of plume migration and hydraulic source containment
in areas that are suspected of being sources of impacts to groundwater. The areas where source
containment would be proposed are the Curriculum Center, Texaco Tutu Service Station, Esso
Tutu Service Station, and OHenry Dry Cleaners. The Texaco Tutu Service Station and the Esso
Tutu Service Station are being addressed through the implementation of the SCPs (see Figure 4-8).
The other potential source areas would be addressed through the installation of source containment
Recovery Wells RW-4 and RW-5. 
Migration of the plume will be addressed through the
installation of plume containment Recovery Wells RW-1, RW-2, and RW-3 (see Figure 4-9).
The source containment would provide hydraulic barriers around source areas, thus
reducing COCs in other parts of the aquifer and would likely reduce the time to reach CGs in other
large portions of the Tutu Wells Site. The plume containment wells will guard against the
continued migration of COCs away from suspected source locations. The recovery well scheme
that would be implemented is the Source and Plume Containment pumping scenario described in
Section 4.6.3.1 (Collection and Containment).
Recovered groundwater would be collected and conveyed to a central treatment facility;
the treated water would be discharged to surface water. The total flow capacity of the treatment
facility would be 100 gpm. Figure 4-11 presents a schematic of the treatment system. All private
wells will be decommissioned within the Tutu Wells Site.
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Property acquisition would be required for the central treatment facility. Sufficient room
would be needed to construct the facility and meet local ordinance set-back requirements. A site
located in the vicinity of the southern plume containment wells is assumed. Such a location would
be at a lower elevation when compared to the rest of the Tutu Wells Site, thus reducing pumping
requirements.
Natural attenuation is proposed for the portions of the plume where groundwater impacts
exist southeast of the Recovery Wells RW-2 and RW-3, and for groundwater below a depth of
approximately ISO feet bis.
The implementation of institutional controls could initially be as extensive as those
proposed in GRA 1, but could be reduced later in the remedial action depending on the
effectiveness of the source area containment. Unauthorized groundwater pumpage will have to be
effectively controlled throughout the remedial action. A monitoring program of the .same scope as
proposed in GRA 1 would also be required.
5.3.4.2 Evaluation of GRA 4
This alternative can adequately address the impact that contaminated groundwater under
the Tutu Wells Site will have to human health. The potential for unauthorized use of groundwater
would still exist. Implementation of institutional controls with plume and source control would
effectively eliminate the potential exposure pathways by which groundwater would present a health
risk.
Geraghty & Miller anticipates that plume and source containment would result in the most
effective approach for reducing constituent concentrations site-wide and would also guard against
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drawing groundwater with a higher constituent concentration toward groundwater with lower
constituent concentrations, thus minimizing contaminant migration within the Tutu Wells Site. The
portions of the plume where natural attenuation is proposed will be naturally remediated over time.
Natural attenuation will effectively reduce COCs below concentrations that could cause impacts to
human health or the environment.
This alternative has the potential for compliance with anticipated ARARs related to
groundwater. However, if DNAPLs are present in the fractured bedrock, as is currently suspected,
remediation of the aquifer as a whole to drinking water quality ARARs will not be feasible. The
effectiveness of natural attenuation meeting chemical-specific ARARs downgradient of Recovery
Wells RW-2 and RW-3 will be contingent on the effectiveness of plume capture. Location-specific
and action-specific ARARs will be met through engineering controls and proper implementation.
Since there may be sources that would continue to be active under this scenario, it is likely that
portions of the aquifer will never meet the MCLs for groundwater without treatment.
The toxicity, mobility, and volume of the impacted groundwater would be reduced. This
GRA would be the most effective alternative in addressing this criterion. The effects of DNAPL
that may be present in the bedrock aquifer would be reduced, and source containment should
decrease the time required to reduce contaminant concentrations within most of the aquifer.
Long-term effectiveness and permanency can be considered favorable. 
The dual
containment program can guard against off-site contaminant migration and can reduce further
impacts caused by source areas. Implementing this program may enable the eventual use of
portions of the aquifer for water supply, although under specific institutional controls. A method
of replacing this source may have to be implemented (e.g., continuing current alternate supply
practices).
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Short-term effectiveness is moderately favorable. There would be minimal impacts related
to implementation of recovery wells and the central treatment facility. The time required to
implement institutional controls and execute well decommissioning would be moderate; however,
the time required for start-up of the treatment system could take an estimated 12 to 18 months.
The installation of recovery wells would be required. Due to the greater number of recovery wells,
GRA 4 would be more expensive than GRA 2 or GRA 3. Well development and monitoring
would be required to ensure the effective capture of groundwater. A permit for discharge to a
surface water would be required and construction time could be longer than for GRA 2 or GRA 3
due to the additional number of recovery wells and the additional piping that must be installed.
Properties would have to be secured for construction of the treatment system, and access
agreements for recovery wells would be required. Personal protective equipment for workers, if
needed, would control exposure during implementation. Assuming this procedure is used, the
estimated time to implement this alternative would be approximately 12 to 18 months.
Implementability would not be favorable as this GRA has the potential for the most
significant administrative requirements. Discharge permits could take 12 to 18 months to secure.
This alternative also places the greatest withdrawal demand on the Tutu aquifer and may create
upconing of mineralized water in areas of the aquifer. Therefore, pre-design studies must carefully
optimize required pumping rates.
The costs to implement this remedial alternative would consist of administrative costs, and
engineering, material, and installation costs related to the collection/containment/treatment and
discharge systems. The costs for GRA 4 would tend to be higher than for other groundwater
remedial alternatives due to the increased amount of materials and installation required.
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The capital cost to implement GRA 4 with the SCPs is approximately $3,175,000. The
estimated total O&M present-worth cost estimated for GRA 4 and the SCPs is $7,328,000. The
estimated grand total cost is $10,503,000 (see Table 5-11).
5.4 COMPARATIVE ANALYSIS OF ALTERNATIVES
In Section 5.1 (Evaluation Criteria), Section 5.2 (Development and Evaluation of Remedial
Alternatives for Soil) and Section 5.3 (Development and Evaluation of Remedial Alternatives for
Groundwater), Geraghty & Miller assembled and evaluated the SRAs and GRAs with respect to
their conformance with the seven evaluation criteria established by NCP guidance. The results of
the evaluations of SRAs are summarized in Table 5-1, and the results of the evaluations of GRAs
are summarized in Table 5-2. This section describes the results of the evaluations conducted and
provides a recommendation for a preferred remedy for each of the seven criteria evaluated and
listed in Section 5.1 (Evaluation Criteria).
5.4.1 Protection of Human Health and the Environment
The protection of human health and the environment is one of two threshold criteria that
must be complied with for the effective implementation of a remedial alternative. The remedy that
is implemented must minimize impacts to human health and the environment.
All of the SRAs, except for SRA 1 (No Action/Institutional Controls) which cannot meet
the requirements of this criterion, are effective in complying with this criterion. Treatment of the
impacted soil (as with SRA 3 or SRA 4) would be preferred because removal of the soil (as in
SRA 5) removes the contaminants, but it does not necessarily reduce the contaminant volume.
SRA 2 (Institutional Controls/Capping) does not involve implementing a treatment technology; it
mitigates migration and exposure. SRA 2 does not reduce the contaminant volume. Therefore,
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either SRA 3 or SRA 4 should be considered the preferred remedy for compliance with protection
of human health and the environment.
Of the GRAs considered, GRA 2, GRA 3, and GRA 4 will meet this criterion as long as
recovery well capture zones are effective and institutional controls are effectively enforced. If
effective capture is not obtained, these remedies will not be folly protective of human health,
especially if natural attenuation does not alleviate the remaining groundwater contaminants.
Therefore, the alternative that provides the most effective capture of impacted groundwater would
be considered the preferred remedy under this criterion. GRA 4 will provide the maximum
protection of human health and the environment because it provides the maximum capture of
impacted groundwater by implementing both plume and source containment. Implementing source
containment will hopefully expedite the remediation of other portions of the aquifer and make these
portions of the aquifer useable some time in the future.
5.4.2 
Compliance with ARARs
Compliance with ARARs is the second threshold criterion (along with protection of human
health and the environment), that must be achieved by a remedial alternative. Compliance with
ARARs relates to a remedy's ability to comply with chemical-, action-, and location-specific
criterion for implementation of a particular remedy. It also refers to the ability of a remedy to meet
other potentially applicable criteria, advisories, or guidance. The most important ARARs for
evaluation of SRAs include the SSLs which are the preliminary CGs and the RCRA LDRs. The
SSLs are actually TBCs rather than ARARs because these are guidance values for soil developed
by the USEPA (CDM Federal Programs 1995b). The RCRA LDRs are also important, especially
when considering excavation and off-site disposal as a remedial alternative. Other ARARs, mainly
associated with permitting (i.e., permit applications and administration, air and water discharge
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limits), can be achieved though proper administration and engineering controls (i.e., treatment
system design).
SRA 1 and SRA 2 do not comply with the SSLs because soil contaminant levels are not
reduced below SSLs. The RCRA LDRs are not applicable to SRA 1 and SRA 2 because no soil
removal is involved in these SRAs. SRA 3, SRA 4, and SRA 5 can comply with the SSLs.
Excavation and disposal proposed in SRA 3, SRA 4, and SRA 5 can comply with the RCRA
LDRs.
Compliance with potential ARARs can be accomplished with all the SRAs except for
SRA 1 and SRA 2. SRA 1 takes no action and SRA 2 reduces exposure and contaminant
migration pathways via capping, but SRA 1 and SRA 2 do not reduce the contaminant levels in
soil. SRA 3 and SRA 4 can comply with this criterion by reducing the toxicity or volume of
impacted soil; SRA 5 can comply with this criterion by removing impacted soil from the site and
disposing the impacted soil in a permitted hazardous waste disposal facility. A preferred remedy
would maximize contaminant reduction and volume and not relocate soil from one area to another
without treatment. Therefore, SRA 3 and SRA 4, which provide for contaminant reduction, would
be the preferred soil remedies for this criterion.
The ARAR requirements for groundwater involve the ability of a remedy to comply with
applicable discharge treatment criteria and regulations. The most important ARARs for the
evaluation of the GRAs are MCLs, TPDES permit requirements, and protection of wetlands. The
MCLs are the preliminary CGs for groundwater, the MCLs are also used as preliminary discharge
limit requirements for the proposed treatment systems. If MCLs are met in the treated water
discharge, TPDES discharge limits for surface-water discharge should also be achieved. Depending
on the final TPDES permit requirements, the discharge limits may be less stringent than MCLs. A
possible wetland area has been identified in the southeast comer of the study area by the USEPA
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Surface-water discharge rates will need to be evaluated to determine if an unacceptable water-level
rise could impact the wetlands. Preliminary evaluation indicates that the large size of the drainage
basin relative to the potential increased surface-water flow should result in little or no hydraulic
impact. However, a more detailed analysis will be required as part of the pre-design activities. All
the GRAs can comply with the potential ARARs except for GRA 1 (No Action/Institutional
Controls). The containment treatment schemes proposed have the ability to meet the anticipated
ARARs. Because GRA 4 is the most aggressive groundwater recovery scenario, GRA 4 is the
preferred alternative to attempt to achieve MCLs in the aquifer.
5.4.3 Short-Term Effectiveness
Short-term effectiveness evaluates the effectiveness of a remedy in protecting human health
and the environment during implementation of the remedy. The least obtrusive remedies causing
the least disturbance would be the most responsive to this criterion.
The SRA that is responsive to the RAOs and would comply with this criterion the best is
SRA 2 (Institution Controls/Capping). In-situ treatment of impacted soil will minimize the fugitive
emissions caused by installation of the remedy and will reduce the off-site impacts related to the
remedial action. This will result in a greater ability to control exposure to potentially hazardous
conditions. Minimizing excavation and transport of impacted soil will also minimize the off-site
impacts due to fugitive emissions or potential accidental releases. Therefore, SRA 2 would seem
to be the most responsive to this criterion.
All of the GRAs can comply with this criterion with the implementation of engineering
controls or safety equipment. However, GRA 1 is not responsive to the RAOs for the site and
would not be implementable due to non-compliance with other NCP criteria. The most effective
remedy to address this criterion would be the remedial action that is responsive to RAOs and
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minimizes the amount of construction or disturbance that is required for installation. Therefore,
GRA 2 would seem to be the most effective GRA at addressing this criterion. The construction
related to GRA 3 and GRA 4 is greater than GRA 2, thus creating more potential for impacts to
workers and residents in the area.
5.4.4 Long-Term Effectiveness
Long-term effectiveness relates to the ability of a remedy to reduce the risks associated
with the potential for exposure, the impacted media at the site, and the adequacy of the remedy in
managing or minimizing the residual risk after the remedial action is complete. In areas where
DNAPL may be present in bedrock, the long-term effectiveness of a remedy may not be
accomplished due to the inefficiencies of locating and removing DNAPLs in bedrock.
The SRA that is responsive to the RAOs and would comply with this criterion would also
be the most reliable in terms of compliance with RAOs in the future. SRA 1 does not meet the
RAOs established for the site. The SRA that addresses this criterion is a remedy that either
removes or reduces impacted soil volume from the site. SRA 3, SRA 4, and SRA 5 all provide this
reliability. SRA 2 is effective at minimizing the transport of impacted soil or leaching of
contaminants; however it requires maintenance and does not totally eliminate potential future
exposure. The actual preferred remedy for this criterion would be based on the effectiveness of
treatment methods that cannot be anticipated until pilot testing is completed at each respective
property. SRA 5 involves the removal of the soil off-site, eliminating the soil source areas from the
property. The removal of impacted soil in SRA 5 will be limited by building foundations and it is
likely that not all of the impacted soil can be removed. Therefore, it would seem be the most
favorable remedies for complying with this criterion are SRA 3 and SRA 4. This is contingent on
the effectiveness of each alternative in meeting the CGs.
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The most effective remedy to address this criterion for groundwater would be the remedial
action that is responsive to RAOs and provides the best potential for remediation of the aquifer.
Therefore, GRA 4 (Source and Plume Containment) would seem to be the most effective GRA at
addressing this criterion because GRA 4 will provide the maximum protection of human health and
the environment and will provide both plume and source containment. GRA 4 will also remove the
most impacted groundwater, thus increasing the amount of mass that can be removed.
5.4.5 Reduction in Toxicitv, Mobility, and Volume
To comply with this criterion, treatment or reduction in contaminant volume must be
provided. The soil remedies that provide treatment of impacted soil are SRA 3 and SRA 4. The
other SRAs considered either do not address the RAOs for the site or do not provide treatment. Of
the two remedies that provide treatment, SRA 4 has the most potential for reducing COCs in soil
because soil would be treated in an engineered environment for contaminant reduction rather than
in situ. Therefore, SRA 4 would be the most responsive SRA to this criterion.
The most responsive GRA to this criterion would be the one that extracts and treats the
most impacted groundwater. This maximizes the reduction in toxicity, mobility, and volume.
GRA 4 is the most active GRA remedy related to groundwater removal and treatment, and
therefore would be the most responsive GRA to this criterion.
5.4.6 Implementabilitv
Implementability deals with the technical and administrative feasibility of implementing an
alternative and the ease with which a remedy can be implemented. Those remedies that can be
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controversial or heavily regulated would be difficult to implement. Implementability also involves
the associated ease of construction and operations or simplicity of the installation and operations.
The SRA that addresses this criterion the most effectively is the remedy that is anticipated
to be the least administratively burdensome, the least controversial, and the most technically
feasible option. Therefore, the remedy that 1) minimizes the permitting requirements, 2) is most
reliable, and 3) minimizes the impacts to residents in the area will be the most administratively
implementable. Of the SRAs evaluated, SRA 2, SRA 3, SRA 4, and SRA 5 are all implementable.
From an administrative perspective, the actual preferred remedy relating to this criterion would be
SRA 3 because it minimizes excavation of impacted soil and also minimizes the required
transportation of impacted soil through residential areas for off-site disposal. From a technical
perspective, the most effective SRA would be SRA 4.
The GRA that would seem to be the most implementable would be GRA 3. This GRA is
the least obtrusive as it minimizes the amount of impact to the area. The treatment system design
for GRA 3 would be more simple to operate, as it would entail the lowest flow rate, and would
require the least amount of equipment and materials to implement.
5.4.7 Cost
The remedial alternative that addresses the RAOs for the site and is the most cost-effective
will be the most responsive to this criterion. Table 5-12 presents a comparative summary of costs.
Of the SRAs considered, the most cost-effective based on the assumptions provided in Appendix C
is SRA 2 (excluding SRA 1 which does not meet the threshold criteria). Of the GRAs considered,
the most cost-effective alternative based on the assumptions provided in Appendix C is GRA 3
(excluding GRA 1 which does not meet the threshold criteria).
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6. PRE-DESIGN ACTIVITIES
Several pre-design activities must be completed before the selected remedy can be
implemented. Some of the additional data that will be needed prior to implementing the selected
remedy are described below. Work plans for pre-design sampling and testing and treatability
studies should be submitted to the USEP A and DPNR for review.
6.1 PRE-DESIGN ACTIVITIES FOR SOIL REMEDIATION
Although a significant amount of data has been gathered to characterize the Tutu Wells
Site, little engineering design data exist that can be used to determine the design parameters for the
proposed SVE systems or for the proposed treatment facility. Prior to implementing SVE at any
of the properties where it is proposed, additional soil sampling (rock sampling at the Curriculum
Center), soil-gas sampling, and pilot testing should be conducted to ensure that the SVE systems
will work effectively.
Air permeability testing of the subsurface to determine soil permeability for SVE is
suggested. This testing should consist of establishing a vacuum on a monitoring well while the air
pressure fluctuations in nearby wells or other subsurface vacuum measuring points are measured.
Additional delineation of soil contamination is needed at two locations. First, the extent
and source of the shallow oily gravel layer and its relationship with the buried PVC pipe west of the
Four Winds Plaza and Western Auto should be determined. Second, soil borings should be
advanced at the center of the high chlorinated VOC soil gas readings north of the building and
through the floor slab in the northwest and west-central portions of the Curriculum Center (former
Laga building) to determine the extent of chlorinated VOCs in the subsurface in these areas.
Sampling of abandoned floor piping inside the building indicated high concentrations of PCE
(approximately 30 percent PCE). This fact, in conjunction with known previous dry cleaning
operations in the northwest corner of the building and the distribution of chlorinated VOCs in
groundwater, indicate that a source of contamination may exist under the building. This source
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should be delineated to determine the extent of contamination, to determine the potential for
continuing releases, and to evaluate appropriate remedial actions (if necessary).
Prior to the implementation of any remedial actions for soil, confirmatory sampling should
be performed. Bioremediation (especially of BTEX constituents) will continue under natural
conditions. Sampling prior to remedial action will address the following objectives:
• 
Confirm the need for remedial action.
• 
Determine soil concentrations prior to remedial action.
• 
Provide additional delineation of the extent of impacted soil.
• 
Provide data for comparison with post-remedial sampling to evaluate the effectiveness
of the remedial action.
6.2 PRE-DESIGN ACTIVITIES FOR GROUNDWATER REMEDIATION
If air sparging or biosparging is selected for groundwater remediation, treatability studies
will be needed to determine the following:
• 
The potential effectiveness of this technology.
• 
Air injection rates that can be achieved.
• 
The radius of influence that can be achieved (to determine sparging well spacing).
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Prior to final design of a groundwater recovery (or extraction) system, it may be necessary
to install and monitor additional wells to further define the following:
• 
The horizontal component of groundwater flow and contaminant trensport.
• 
The horizontal and vertical extent of contamination.
• 
The hydraulic characteristics of the aquifer in the areas of recovery or extraction.
The number of recovery wells and their locations presented in this FS Report are
preliminary and may be modified and optimized based on updated pre-design data. During pre-
design, it may be necessary to use a predictive model to simulate the movement of groundwater
and contaminants under various extraction well scenarios (e.g., number of wells, rates of
extraction).
Once a groundwater recovery system is designed, it may be necessary to install additional
wells to monitor the effectiveness of groundwater recovery (i.e., capture zones). Once the
recovery or extraction wells are installed, pumping tests will be needed to determine their yield and
the concentrations of contaminants in the recovered groundwater.
6.3 PRE-DESIGN ACTIVITIES FOR TREATMENT SYSTEMS
The treatment systems used for groundwater and SVE will require more specific data
regarding influent concentrations and to evaluate the need for a treatment component for the air
discharge is necessary. A discharge monitoring plan should be prepared for air discharges and
treated water discharges. An assessment of the potential impacts on a USEPA-identified wetland
may be a necessary component of the discharge to surface-water permit application. An evaluation
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of the potential magnitude of water-level rise and associated hydraulic impact of the discharge on
the wetland may be needed. If a potentially significant water-level rise is predicted, a delineation of
the wetland may be necessary. A preliminary review of the drainage basin characteristics seems to
indicate that no detrimental impact would be created; this may need to be further evaluated during
the permit application.
Groundwater containment and treatment facility design will require installation of test
recovery wells and aquifer pumping tests to determine the actual zones of hydraulic capture and the
number and spacing of the recovery wells needed. In addition, pilot testing may needed to evaluate
the effectiveness of the proposed technologies for treating groundwater contamination.
Property acquisition, as discussed in Appendix C, will be required for a site for the
construction of a central treatment facility. Figure 5-1 shows a conceptual layout for piping and
the treatment system. A site evaluation would be required to find the most appropriate location.
Additional evaluation of natural inorganic groundwater concentrations may be needed. The
existing groundwater at the Tutu Wells Site has high naturally occurring concentrations of
inorganic parameters not related to the COCs at the site (e.g., TDS, 
manganese, iron, and
chloride). These inorganic parameters could also impact the overall operations of the central
treatment facility due to the potential need for pretreatment (e.g., precipitation of metal oxides or
salts). The need for sequestering agents to address this concern will have to be confirmed during
the pre-design activities. Actual influent data from pumping tests and a pilot study will be needed
to provide final design requirements for the central treatment facility.
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7. REFERENCES
Camp, Dresser & McKee (CDM) Federal Programs Corporation. 1992. Letter to C. Kwan, U.S.
Environmental Protection Agency. Re: Technical Memorandum I. April 24,1992.
Camp, Dresser & McKee (CDM) Federal Programs Corporation. 1995a. Final Endangerment
Assessment, Tutu Wells Site, St. Thomas, U.S. Virgin Islands. 3 Volumes, EPA Work
Assignment No. 073-2P1D, Contract No. 68-W9-0024. January 12, 1995.
Camp, Dresser & McKee (CDM) Federal Programs Corporation. 
1995b. Final Report -
Estimation of Soil Cleanup Concentrations Required to Protect Groundwater as a Source
of Drinking Water, Tutu Wells Site, St. Thomas, U.S. Virgin Islands. Work Assignment
No. 073-2P1D. Document Control No. 7720-073-FR-CGTV. July 11,1995.
Cooper Environmental, Inc. 1993. Site Investigation Report, Ramsay Motors, Tutu, St. Thomas,
U. S. Virgin Islands. CEI Project No. 92115. December 8,1993.
Department of Conservation and Cultural Afiairs, St. Thomas, Virgin Islands. 
1979.
Environmental Laws and Regulations of the Virgin Islands. Reprinted from Titles 12 and
19 of the Virgin Islands Code and the Virgin Islands Rules and Regulations.
ENSR Consulting and Engineering (ENSR). 1994. Four Winds Plaza, Western Auto, St.
Thomas, U. S. Virgin Islands, Closure Report for Underground Storage Tanks. Document
Number 7218-001-200. June 1994.
Erler & Kalinowski, Inc. (EKI). 1995a. Groundwater arid Soil Remediation Program for Texaco
Tutu Service Station, St. Thomas, U.S. Virgin Islands. April 13,1995.
Erier & Kalinowski, Inc. (EKI). 1995b. Technical Memorandum I, Basis for Design of the
Groundwater and Soil Remediation, Source Control Program, Texaco Tutu Service
Station, St. Thomas, U.S. Virgin Islands. June 1995.
Forensic Environmental Services, Inc. (FES). 1995. (See Appendix B, page 2)
Geraghty & Miller, Inc. 1983. Report on Current Groundwater Conditions in the U.S. Virgin
Islands. Prepared for the U.S. Virgin Islands Department of and Cultural Affairs, April
1983,80pp.
Geraghty & Miller, Inc. 1992a. Tutu Service Station Investigation Work Plan, St. Thomas, U.S.
Virgin Islands. March 1992.
Geraghty & Miller, Inc. 1992b. Technical Memorandum I, Tutu Service Station Investigation, St.
Thomas, U.S. Virgin Islands. April 1992.
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Geraghty & Miller, Inc. 1993a. Technical Memorandum n, Tutu Service Station Investigation,
St. Thomas, U.S. Virgin Islands. May 1993.
Geraghty & Miller, Inc. 1993b. Phase n Remedial Investigation Work Plan, Tutu Wells Site, St.
Thomas, U.S. Virgin Islands. December 1993.
Geraghty & Miller, Inc. 1993c. Eighth Sampling Report, March/April 1993, Tutu Wells Site, St.
Thomas, U.S. Virgin Islands. July 1993.
Geraghty & Miller, Inc. 1995. Final Phase H Remedial Investigation Report, Tutu Wells Site, St.
Thomas, U.S. Virgin Islands. April 6, 1995.
Graves, R.P., and R. Gonzales. 1988. Potentiometric Surface of the Turpentine Run Aquifer in the
Tutu Area, Eastern St. Thomas, U.S. Virgin Islands. September 1987. 
U.S. Geological
Survey, Water Resources Investigation Report 88-4131.
Howard, Philip H., and others. 1991. 
Handbook of Environmental Degradation Rates. Lewis
Publishers, Inc. Second Printing 1991.
Jordan, D.G., and O.J. Cosner, 1973. A Survey of the Water Resources of St. Thomas, Virgin
Islands, U.S. Geological Survey Open-File Report, 55 pp.
Jordan, D.G., and D.W. Fisher. 1977. Relation of Bulk Precipitation and Evaporation to Water
Quality and Water Resources, St. Thomas, U.S. Virgin Islands. U.S. Geological Survey
Water-Supply Paper 1663-1.
Keller, G.V. 1960. 
Physical Properties of Tuffs in the Oak Spring Formation, Nevada. U.S.
Geological Survey Professional Paper 400-B.
Mobil. 1992. Off-Gas Treatment Systems for Soil/Groundwater Remediation Systems. Mobil
U.S. Marketing Division, Environmental Bulletin No. 04-050/3-92/04. March 9,1992.
Stevens, K.E., F. Gomez-Gomez, and J. Alicia. 1981. Water Wells in the U.S. Virgin Islands, Part.
1, St. Thomas, U.S. Geological Survey Open-File Report 82-82.
U.S. Census Bureau. 1990. Population Data for the Tutu Subdistrict of St. Thomas, U.S. Virgin
Islands.
U.S. Environmental Protection Agency (USEPA). 1987. Guidelines for Delineation of Wellhead
Protection Areas, U.S. EPA, Office of Groundwater Protection. EPA 440/6-87-010. June
1987.
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U.S. Environmental Protection Agency (USEPA). 1988a. Guidance for Conducting Remedial
Investigations and Feasibility Studies Under CERCLA-Interim Final. EPA/540/G-89/W04.
OSWER Directive No. 9355.3-01.
U.S. Environmental Protection Agency (USEPA). 1988b. Guidance on Remedial Actions for
Contaminated Groundwater at Superfund Sites. EPA/540/G-88/003. OSWER Directive
No. 9283.1-2.
U.S. Environmental Protection Agency (USEPA). 1990. Administrative Order No. 11-9003-0401,
March 22,1990.
U.S. Environmental Protection Agency (USEPA). 1991a. Hazardous Ranking System (HRS)
Documentation Record, Tutu Wellfield. August 1991.
U.S. Environmental Protection Agency (USEPA). 
1991b. 
Risk Assessment Guidance for
Superfund: Vol. 1 Human Health Evaluation Manual (Part 8, Development of Risk Based
Preliminary Remediation Goals-Interim). OSWER Directive 9285.7-01B.
U.S. Environmental Protection Agency (USEPA). 1991c. Delineation of Wellhead Protection
Areas in Fractured Rocks. EPA 570/9-91-009. June 1991.
U.S. Environmental Protection Agency (USEPA). 1992a. Administrative Order on Consent No.
n-RCRA-7003 and 9003-92-0401. February 19,1992.
U.S. Environmental Protection Agency (USEPA). 1992b. Estimating Potential Occurrences of
DNAPL at Superfund Sites. Publication: 9355.4-07FS. January 1992.
U.S. Environmental Protection Agency (USEPA). 
1993. Presumptive Remedies: Site
Characterization and Technology Selection for CERCLA Sites with Volatile Organic
Compounds in Soils. EPA/540/F-93/048. OSWER Directive No. 9355.0-48FS.
U.S. Environmental Protection Agency (USEPA). 1994a. Letter to A.G. Ramos, Designated
Coordinator for the TEIC from C. Petersen, USEPA Chief for Region H Superfund New
York/Caribbean Branch. Re: Approval of the Phase H RI Work Plan, Tutu Wells, Site,
St. Thomas, U.S. Virgin Islands. March 17,1994.
U.S. Environmental Protection Agency (USEPA). 1994b. Letter to J. McBurney and G. Seibel,
TEIC Designated Coordinator. 
Re: 
Comments on the Draft Phase n Remedial
Investigation and Development and Screening of Remedial Alternatives Report. December
28,1994.
g:\aproject\tutu\prOO 13.037\reports\tutufs.doc
GERAGHTY & MILLER, INC.
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U.S. Environmental Protection Agency (USEPA). 1994c. Technical Background Document for
Draft Soil Screening Level Guidance. 
PA-540/R-94/0-18 OSWER Directive No.
9355.4-14.
U.S. Geological Survey (USGS). 1973. Water Records of U.S. Virgin Islands, 1962-69. Robison,
T. M. and other (Authors). United States Department of the Interior Geological Survey
prepared in cooperation with the National Park Service and the Government of the Virgin
Islands of the United States.
Weston/Spill Prevention and Emergency Response (SPER), Division n TAT. 1988. Memorandum
from Amaldo Martinez, TAT H PM and Douglas Henne, TAT H-QC to Carlos OTSTeill,
USEPA Caribbean Field Office. Re: St. Thomas, Tutu HSL Sampling RTAT-02-F-
04398. January 27,1988.
Weston/Spill Prevention and Emergency Response (SPER), Division n TAT. 1989. Memorandum
to L.E. Santos, OSC, EPA Caribbean Field Office. Re: Final Results of the November
1988 TCL Sampling and Comparison to TCL Sampling Conducted October 1987. May 1,
1989.
g:\aproject\tutu\pfOO 13.037teports\lutufs.doc
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Table 2-1. Summary of Soil Screening Levels Provided by the U.S. Environmental Protection
Agency, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Property
Depth
(ft bis)
Chlorinated
VOCs
(ppb)
BTEX
Compounds
(ppb)
Curriculum Center 
0.0-2.8 
731 
150
(former LAGA Facility) 
2.8 - 35.0 
73 
37
Texaco Tutu Service Station 
0.0 - 8.7 
290 
67
8.7- 15.0 
29 
13
Esso Tutu Service Station 
0.0-4.0 
320 
74
4.0-15.0 
32 
15
O'Henry Dry Cleaners 
0.0 - 1.6 
375
1.7-22.0 
31
Other propertiesm 
0.0-4.0 
320 
74
4.0-15.0 
32 
15
Soil screening levels are based on site-specific estimates for leaching of contaminants that may
result in exceedance of groundwater drinking standards (CDM Federal Programs Corporation 1995b).
ft bis 
Feet below land surface.
VOCs Volatile organic compounds.
BTEX 
Benzene, toluene, ethylbenzene, and xylenes.
ppb 
Parts per billion, equivalent to micrograms per kilogram (ug/kg).
No values provided.
m 
The U.S. Environmental Protection Agency (USEPA) directed the use of soil screening levels
for the Esso Tutu Service Station at all other properties.
G:\APROJECTYrUTU\Pft0013.037\DATA\SOILCLN.XLS
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Table 2-2. Summary of Carcinogenic Risks Exceeding the U.S. Environmental Protection Agency Guidance Value,
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Media
Groundwater
(Sitewide)
Surface soil
(Tillett property)
Receptor Population 
Exposure Routes
Adult residents 
Ingestion
Children 
Ingestion
(0 to 6 years)
Site worker 
Ingestion
Adult residents 
Ingestion
Children 
Ingestion
(0 to 6 years)
Total Pathway 
Individual RME Values
RME Value 
Contributing the Greatest Risks
6.6 xlO"4 
PCE
Vinyl chloride
3.1 x 10"4 
Vinyl chloride
2,0 xW4 
Vinyl chloride
4.4 xW* 
ArocloM242
Arsenic
3.0 x10'3 
Aroclor1242
Arsenic
1.2 x
4.5 x
2.1 x
1.3x
4.3 x
8.2 x
I.Ox
1.9x
104
10"4
10-4
10-4
104
ID'6
10'3
10'5
c--i
RME 
Resonable maximum exposure.
PCE 
Tetrachloroethene.
Source: 
COM Federal Programs Corporation (1995a).
G:\APROJECTYT UTU\PR0013.037\DATA\CARCRISK.XLS
GERAGHTY & MI LI PR, INC.
Table 2-3. Summary of Noncarcinogenic Risks Exceeding the U.S. Environmental Protection Agency Hazard Quotient of 1,
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Media
Receptor Population
Total Pathway
Exposure Routes 
HI
Individual HQs Contributing
the Greatest Risks
Groundwater 
Adult residents 
Ingestion 
1.9x10ot 
Total DCE
Manganese
Children 
Ingestion 
6.7 x 1001 
Total DCE
(0 to 6 years) 
PCE
Manganese
Antimony
Vanadium
1.2x 10°
2.6 x 10°
2.8 x 10°
1.3x 10°
6.0 x 10°
1.6x 10°
1.0x 10°
Site worker 
Ingestion
Future construction worker 
Ingestion
1.0x 10',01
9.1 x 10',01
Manganese 
9.2 x 10
Manganese 
8.2 x 10°
L.
H-4i
H-
Surface soil
(Tillett property)
Children
(0 to 6 years)
Ingestion
Inhalation
3.0 x 1001
3.1 x 1001
Manganese
Arsenic
Manganese
2.2 x 10°
4.3 x 10°
3.1 x 10°
HI 
Hazard index.
HQ 
Hazard quotient.
DCE 
1,2-Dichloroethene.
PCE 
Tetrachloroethene.
Source: 
CDM Federal Programs Corporation (1995a).
G:\APROJECT\TUTU\PR0013.037\DATA\NONCARC.XLS
GERAGHTY & MILLER. INC
Page 1 of 4
Table 2-4. Summary of Analytes Detected in Soil above Soil Screening Levels at the Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Property
Chlorinated VOC Constituents
Curriculum Center
Esso Tutu Service Station
O' Henry Dry Cleaners
BTEX Constituents
Curriculum Center
Ramsay Motors
Parameter
1,1,1 -Trichloroethane
Tetrachloroethene
1,1,1 -Trichloroethane
Trichloroethene
1 , 1 -Dichloroethane
1 ,2-Dichloroethene(trans)m
Tetrachloroethene
Trichloroethene
Benzene
Toluene
Ethyl benzene
Xylenes
Benzene
Ethylbenzene
Depth
(ft bis)
0.0 - 2.8
0.0 - 4.0
4.0- 15.0
4.0- 15.0
4.0 - 1 5.0
0.0 - 4.0
4.0- 15.0
0.0 - 4.0
4.0- 15.0
0.0- 1.6
1 .7 - 22.0
1 .7 - 22.0
0.0 - 2.8
0.0 - 2.8
0.0 - 2.8
0.0 - 2.8
4.0 - 1 5.0
0.0 - 4.0
4.0- 15.0
SSLs
(ug/kg)
731
320
32
32
32
320
32
320
32
375
31
31
150
150
150
150
15
74
15
Sample
Name
TWS-03
B-103
SS-3
SS-7
SS-8
SS-7
SS-8
SS-8
SS-3
SS-8
SS-3
SS-7
SS-8
e-01
e02-02
OHSS-1
OHSS-1
OHSS-1 FR
B-13
e02-02
SS-12
TWS-03
SS-12
TWS-03
SS-12
TWS-03
SS-12
TWS-03
HB-2
HB-5
HB-2
Sample Interval
(ft bis)
0.0 - 0.3
0.0 - 1 .0
3.0
5.0
7.0
5.0
7.0
7.0
3.0
7.0
3.0
5.0
7.0
(Surface Soil)
1 .5 - 2.5
2.0
5.0
8.0
5.0
4.0 - 6.0
1 .5 - 2.5
0.0 - 0.5
0.0 - 0.3
0.0 - 0.5
0.0 - 0.3
0.0 - 0.5
0.0 - 0.3
0.0 - 0.5
0.0 - 0.3
4.5
2.3
4.5
Concentration
(ug/kg)
1,800
394
1,100
520
1,500
44
58
45
560
70
3,200
75
110
440,000 «
180,000
5,400 D
59,000 D
400 J
22,000
200 D
75
6,300 J
2,700
270,000
500,000
1 2,000 J
47,000
77,000
420,000
17 J
190 J
290
See last page for footnotes.
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Page 2 of 4
Table 2-4. Summary of Analytes Detected in Soil above Soil Screening Levels at the Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Property 
Parameter 
Depth 
SSLs 
Sample
(ft bis) 
(ug/kg) 
Name
Texaco Tutu Service Station 
Benzene 
0.0-8.7 
67 
TT-1D
TT-1D FR
Ethylbenzene 
0.0 - 8.7 
67 
OW/SB-1
TT-1D
TT-1DFR
8.7-15.0 
13 
OW/SB-1
Esso Tutu Service Station 
Benzene 
0.0 - 4.0 
74 
SS-3
TP-3
TP-5
TP-8
4.0-15.0 
15 
B-102
SS-7
SS-8
Toluene 
0.0 - 4.0 
74 
SS-3
SS-4
SS-5
SW-3
TP-3
TP-6
4.0-15.0 
15 
B-101
SS-1
SS-7
SS-8
Ethylbenzene 
0.0 - 4.0 
74 
SS-3
SS-4
SS-5
SW-3
TP-8
TP-5
TP-6
4.0-15.0 
15 
B-101
B-102
B-103
SS-1
SS-7
SS-8
Sample Interval
(ft bis)
4.5 - 5.0
4.5 - 5.0
6.5
4.5 - 5.0
4.5 - 5.0
9.5
3.0
(Northeast Roor)
(Center Floor)
(South)
10.0- 12.0
5.0
7.0
3.0
3.0
3.0
0.0 - 2.0
(Northeast Floor)
(East Floor)
8.0- 10.0
10.0- 12.0
9.0
5.0
7.0
3.0
3.0
3.0
0.0 - 2.0
(South Wall)
(Center Floor)
(East Floor)
10.0- 12.0
4.0 - 6.0
8.0- 10.0
10.0- 12.0
7.0-7.5
9.0
5.0
7.0
Concentration
(ug/kg)
(170)
69
(630)
110 / (210)
140
67 / (50)
880
230 J
1,100
93
625
160
270
53,000
4,600
6,500
520
5,200
180,000
28
548
46,000
33,000
51,000
1 1 ,000
990
520
170
520
7,000
55,000
304
58
1,117
1,037
26
12,000
1,700
11,000
See last page for footnotes.
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Page 3 of 4
Table 2-4. 
Summary of Analytes Detected in Soil above Soil Screening Levels at the Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
j<^^^**\
Property 
Parameter 
Depth 
SSLs 
Sample
(ft bis) 
(ug/kg) 
Name
Esso Tutu Service Station 
Xylenes 
0.0 - 4.O 
74 
SS-3
(continued) 
SS-4
SS-5
SW-3
TP-2
TP-3
TP-6
TP-7
TP-8
4.0-15.0 
15 
B-101
B-102
SS-1
SS-7
SS-8
Western Auto
Benzene 
0.0-4.0 
74 
SS-1
4.0 - 1 5.0 
15 
SS-6
T1-2
Toluene 
0.0-4.0 
74 
SS-1
T2-AS
T2-ASRE
4.0-15.0 
15 
MW-24-2
T1-3
T1-4
T2-1S
T2-3S
Ethytbenzene 
0.0 - 4.0 
74 
SS-1
SS-2
T2-AS
T2-ASRE
T2-SN
T2-4S
4.0 - 1 5.0 
15 
SS-4
SS-5
SS-6
SS-7
SS-8
SS-9
T1-1
T1-2
T1-3
T1-4
T2-1S
T2-2S
T2-3S
Sample Interval
(ft bis)
3.0
3.0
3.0
0.0 - 2.0
(North Floor)
(Northeast Floor)
(East Floor)
Southwest Floor
(South Wall)
8.0- 10.0
10.0- 
12.0
8.0- 
10.0
10.0- 
12.0
9.0
5.0
7.0
2.0
5.0 - 6.0
4.0
2.0
0.0 - 0.5
0.0 - 0.5
4.0 - 6.0
4.0
4.0
6.7
6.7
2.0
3.0
0.0 - 0.5
0.0 - 0.5
1 .0 - 1 .5
1 .0 - 1 .5
5.0 - 6.0
5.0 - 6.0
5.0 - 6.0
5.0 - 6.0
5.0
5.0
4.0
4.0
4.0
4.0
6.7
6.7
6.7
Concentration
(ug/kg)
77,400
24,200
29,000
1,170
1,600E
31, 000 E
540,000
300 E
220
168
2,295
1,141
575 **
80,400
58,000
78,000
140
34
29 J
3,900
760 J
800 J
(34)
25 J
16J
28 J
740 J
1,600
850
890 J
1,OOOJ
230
150
37
100
420
270
340
290
100
240
20 J
16J
230
29 J
980 J
See last-page for footnotes.
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Page 4 of 4
Table 2-4. Summary of Analytes Detected in Soil above Soil Screening Levels at the Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Property
Western Auto
(continued)
Parameter 
Depth 
SSLs 
Sample
(ft bis) 
(ug/kg) 
Name
Xylenes 
0.0-4.0 
74 
SS-1
SS-2
T2-AS
T2-ASRE
T2-SN
4.0-15.0 
15 
SS-4
SS-5
SS-6
SS-8
T1-1
T1-2
T2-1S
T2-2S
T2-3S
Sample Interval
(ft bis)
2.0
3.0
0.0 - 0.5
0.0 - 0.5
1 .0 - 1 .5
5.0 - 6.0
5.0 - 6.0
5.0 - 6.0
5.0
4,0
4.0
6.7
6.7
6.7
Concentration
(ug/kg)
34,000
501
5,800
6,100
120
128
125
2,700
53
85
210
430
51 J
7,000
SSLs based on USEPA-subcontractor (COM Federal Programs Corp. 1995b) report on vadose zone modeling. Criteria are site-
specific, except for data from soil samples collected from Western Auto and Ramsay Motors, which are screened against
criteria applicable to the Esso Tutu Service Station.
Data reported in parentheses at Western Auto are from soil samples collected by ENSR Consulting & Engineering , Inc.
Data reported in parentheses at the Texaco Tutu Service Station are from soil samples collected by Blasland, Bouck & Lee, Inc.
* 
Reported by the U.S. Environmental Protection Agency as tetrachloroethane; this is believed to be a
typographical error.
** 
Result includes only methylxylene; o- and p-xylene data not available.
111 
1,2-Dichloroethene (1,2-DCE) results reported as total 1,2-DCE and SSL applies to the trans-1,2-DCE isomer.
SSLs 
Soil Screening Levels. SSLs provided by the USEPA (COM Federal Programs Corporation 1995b); see note above.
BTEX 
Benzene, toluene, ethylbenzene, and xylenes.
FR 
Field replicate.
VOC 
Volatile organic compound.
J 
Result detected below reporting limit and/or an estimated concentration.
D 
Analyte identified at a secondary dilution.
E 
Exceeds instrument calibration range.
ug/kg 
Micrograms per kilogram, equivalent to parts per billion (ppb).
ft bis 
Feet below land surface.
USEPA 
U.S. Environmental Protection Agency.
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Page 1 of 5
Table 3-1. Groundwater Chemical-Specific Remedial Action Levels Identified for the
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Parameters
Groundwater RALs
USEPA
MCLs
(mg/L)
MCLGs
(mg/L)
Inorganics
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Selenium
Silver
Sodium
Thallium
Vanadium
Zinc
Cyanide
Nitrate (as N)
Chloride
pH (units)
Total dissolved solids
Volatile Organic Compounds
Chloromethane
Bromomethane
Vinyl chloride
Chloroethane
Methylene chloride
Acetone
0.05 to 0.20 m
0.006
0.05
2.0
0.004
0.005
0.1
0.3 (1)
TT
0.05
0.002
0.1
0.05
0.1
0.002
5.0
0.2
10.0
250 '"
6.5-8.5
500 
m
0.006
2.0
0
0.005
0.1
1.3
0
0.002
0.1
0.05
0.0005
0.2
10.0
0.002
0.005
0
See last page for footnotes.
G:\APHOJECTVTUTU\PROO13.037\DAT A\CHEM.XLS
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Page 2 of 5
Table 3-1. Groundwater Chemical-Specific Remedial Action Levels Identified for the
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Parameters
Groundwater RALs
USEPA
MCLs
(mg/L)
MCLGs
(mg/L)
Volatile Organic Compounds (continued)
Carbon disulfide
1,1 -Dichloroethene
1,1 -Dichloroethane
1,2-Dichloroethene(cis)
1,2-Dichloroethene(trans)
Chloroform
1,2-Dichloroethane
2-Butanone
1,1,1 -Trichloroethane
Carbon tetrachloride
Vinyl acetate
Bromodichloromethane
1,1,2,2-Tetrachloroethane
1,2-Dichloropropane
trans-1,2-Dichloropropene
Trichloroethene
Dibromochloromethane
1,1,2-Trichloroethane
Benzene
cis-1,3-Dichloropropene
Bromoform
2-Hexanone
4-Methyl-2-pentanone
Tetrachloroethene
Toluene
Chlorobenzene
Ethylbenzene
Styrene
Total xylenes
Pesticides/PCBs
alpha-BHC
beta-BHC
delta-BHC
gamma-BHC(Lindane)
Heptachlor
Aldrin
0.007
0.07
0.1
0.005
0.2
0.005
0.005
0.005
0.005
0.005
0.7
0.1
10
0.007
0.07
0.1
0.2
0
0.003
0
0
1
0.7
0.1
10
0
0
See last page for footnotes.
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Page 3 of 5
Table 3-1 . Groundwater Chemical-Specific Remedial Action Levels Identified for the
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Groundwater RALs
USEPA
Parameters 
MCLs 
MCLGs
(mg/L) 
(mg/L)
Pesticides/PCBs, continued
Heptachlor epoxide
Endosulfan I
Dieldrin
4,4'-DDE
Endrin 
0.002 
0.002
Endosulfan II
4,4'-DDD
Endosulfan sulfate
4,4'-DDT
Methoxychlor 
0.04 
0.04
Chlordane(alpha and/or gamma) 
- 
0
Toxaphene 
0.003 
0
Aroclor1016
Aroclor1221
Aroclor 1 232
Aroclor 1 242
Aroclor 1 248
Aroclor 1 254
Aroclor 1 260
Endrin ketone
Semivolatile Organic Compounds
Phenol(s)
bis(-2-Chloroethyl)ether
2-Chlorophenol
1 ,3-Dichlorobenzene 
0.6 
0.6
1 ,4-Dichlorobenzene 
0.075
Benzyl alcohol
1,2-Dichlorobenzene 
0.6 
0.6
2-Methylphenol
bis(2-Chloroisopropyl)ether
4-Methylphenol
N-Nitroso-di-propylamine 
-
Hexachloroethane
Nitrobenzene
Isophorone
2-Nitrophenol
See last page for footnotes.
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Page 4 of 5
Table 3-1 . Groundwater Chemical-Specific Remedial Action Levels Identified for the
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Groundwater RALs
USEPA
Parameters 
MCLs 
MCLGs
(mg/L) 
(mg/L)
Semivolatile Organic Compounds (continued)
2,4-Dimethylphenol
Benzoic acid
bis(2-Chloroethoxy)methane
2,4-Dichlorophenol
1 ,2,4-Trichlorobenzene 
0.07 
0.07
Naphthalene
4-Chloroaniline
Hexachlorobutadiene
4-Chloro-3-methylphenol
2-Methylnaphthalene
Hexachlorocyclopentadiene 
0.05 
0.05
2,4,6-Trichlorophenol 
-
2,4,5-Trichlorophenol
2-Chloronaphthalene 
- 
-
2-Nitroaniline
Dimethylphthalate
Acenaphthylene
3-Nitroaniline
Acenaphthene
2,4-Dinitrophenol
4-Nitrophenol
Dibenzofuran
2,4-Dinitrotoluene
2,6-Dinitrotoluene
Diethylphthalate
4-Chlorophenyl-phenylether
Fluorene
4-Nitroaniline
4, 6-Dinitro-2-methylphenol
N-Nitrosodiphenylamine
4-Bromophenyl-phenylether
Hexachlorobenzene 
0.001 
0
Penta-chlorophenol 
0.001 
0
Phenanthrene
Anthracene
Di-n-butylphthalate
Fluoranthene
See last page for footnotes.
G:\APROJECT\TirrU\PROO13.037\DATA\CHEM.XLS
GERAGHTY & MILLER, INC. 
TUT OO7 2.149
Page 5 of 5
Table 3-1. Groundwater Chemical-Specific Remedial Action Levels Identified for the
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Groundwater RALs
Parameters
USEPA
MCLs
(mg/L)
MCLGs
(mg/L)
Semivolatile Organic Compounds (continued)
Pyrene 
--
Butylbenzylphthalate 
0.1 (P)
3,3'-Dichlorobenzidine
Benzo(a)anthracene 
0.0001 (P)
bis(2-Ethylhexyl)phthalate 
0.006
Chrysene
Di-n-octyl phthalate
Benzo(b)fluoranthene 
0.0002 (P)
Benzo(k)fluoranthene
Benzo(a)pyrene 
0.0001
lndeno(1,2,3-cd)pyrene 
0.0004 (P)
Dibenz(g,h)anthracene 
0.0003 (P)
Benzo(g,h,i)perylene
0 (P)
0 (P)
0
0 (P)
0
0 (P)
0 (P)
All RALs expressed in milligrams per liter (mg/L) unless indicated.
Currently, there are no federal standards for soil or sediment.
mg/L 
Milligrams per liter.
TT 
Treatment Technique (Action Levels: Copper 1.3 mg/L, lead 0.015 mg/L).
Values determined by USEPA.
111 
Value classified as a Secondary Maximum Contaminant Level (SMCL).
USEPA 
U.S. Environmental Protection Agency.
RALs 
Remedial Action Levels.
MCLs 
Maximum contaminant levels.
MCLGs 
Maximum contaminant level goals.
PCBs 
Polychiorinated biphenyls.
No standard available.
(P) 
Proposed.
G:\APROJECT\TUTU\PR0013.037\DATA\CHEM.XLS
GERAGHTY & MILLER, INC.
TUT 
O07 
2 ISO
Page 1 of 4
Table 3-2. Summary of Potential Federal Location-Specific Applicable or Relevant and Appropriate Requirements, Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
Requirement
Applicable or Relevant
and Appropriate
Requirements
Comments
Protection of Floodplains
E.O. 11988, 40CFR6AppA
Requires the USEPA to minimize potential harm to
or within floodplains.
Yes
Portions of the Tutu Wells Site lie within the
boundaries of a 100-year floodplain.
Protection of Wetlands
E.O. 11990, 40 CFR 6 App A; 40 CFR 230
Requires the USEPA to minimize potential harm to or
within wetlands.
Fish and Wildlife Coordination Act
16 USC §661 et seq.i; 30 CFR 340/330; 40 CFR 6
Protects fish and wildlife resulting from control or
structural modification of a natural stream or body
of water.
Yes
No
Wetland area has been identified the USEPA
adjacent to the Tutu Wells Site. Remedial activities
are not anticipated to disturb this area.
Remedial activities are not expected to impact the
wildlife present at the Tutu Wells Site.
Endangered Species Act
16 USC §1531 et seq.; 50 CFR 200, 402
Protects endangered and threatened species and
preserves their habitat.
Yes
Endangered species (Epicrates monensis grant!) and
critical habitat (Zanthoxylem thomasianium) were
identified in the Endangerment Assessment for the
Tutu Wells Site. Remedial activities are not expected
to impact endangered species or critical habitats.
See last page for footnotes.
g:\aproject\tutu\prO013.037\data\FLSARAR.XLS
GERAGHTY & MILLER, INC
Page 2 of 4
Table 3-2. Summary of Potential Federal Location-Specific Applicable or Relevant and Appropriate Requirements, Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
Requirement
Applicable or Relevant
and Appropriate
Requirements
Comments
Wilderness Act
16 USC §1131 et seq.; 50 CFR 35
Limits activities within an area designated as a
wilderness area.
National Wildlife Refuge System
16 USC §668; 50 CFR 27
Limits activities within a national wildlife refuge.
Wild and Scenic Rivers Act
16 USC §1271 et seq.; 40 CFR 6.302(e)
Protects rivers that are designated as wild, scenic,
or recreational.
No
No
No
The proposed remedial actions are not within a
federally owned area designated as a wilderness area.
The proposed remedial actions are not within an area
designated as part of the National Wildlife Refuge System.
The Tutu Wells Site is not near a wild, scenic, or
recreational river.
—!
C
National Historic Preservation Act
16 USC §470; 36 CFR 60, 63, 65
Requires preservation of properties listed on or
eligible for listing on the National Register of Historic
Places or the National Historical Landmark Program.
No
No historic, architectural, or cultural resources included
on either of the national lists are located in areas where
remedial actions are planned.
See last page for footnotes.
til
Ki
g:\aproject\tutu\prO013.037\data\FLSARAR.XLS
GERAGHTY & MILLER, INC.
Page 3 of 4
Table 3-2. Summary of Potential Federal Location-Specific Applicable or Relevant and Appropriate Requirements, Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
Requirement
Applicable or Relevant
and Appropriate
Requirements
Comments
Clean Water Act Section 404
33 USC §1344, 40 CFR 230, 33 CFR 320-330
Requires permit for discharge of dredged or fill
material into waters of the United States, including wetlands.
No
Remedial activities will not involve discharge of
dredged or fill material.
Coastal Zone Management Act
16 USC §1451, 15 CFR 928, 40 CFR 6.302(d)
Requires approval by the state coastal zone
management program (CZM) for actions affecting the
coastal zone, including lands thereunder and
adjacent shorelands.
Rivers and Harbors Act
33 USC §403, 33 CFR 32-330
Regulates activities in navigable waters in the United States
No
No
The site is not within an area designated as a coastal
zone.
The Tutu Wells Site is not near navigable waters.
c
-H
See last page for footnotes.
en
g:\aproject\tutu\prO013.037\data\FLSARAR.XLS
GERAGHTY & MILLER, INC
Page 4 of 4
Table 3-2. Summary of Potential Federal Location-Specific Applicable or Relevant and Appropriate Requirements, Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
Requirement
Applicable or Relevant
and Appropriate
Requirements
Comments
Marine Protection. Research and Sanctuaries Act
15 CFR 922; 33 CFR 324
Requires a permit to dump any material into the
ocean waters of the United States.
No
Remedial activities will not involve dumping of
material into ocean waters.
Manages designated marine environments of
special national significance.
No
The Tutu Wells Site does not meet the criteria as a
national marine sanctuary.
Outer Continental Shelf Act
33 CFR 322
No
The site is not within an area designated by this act.
Requires a permit for structures or work in or
affecting navigable United States water.
Archaeological and Historic Preservation Act
16 USC §469; 40 CFR 6.301 (a)
Limits activities in the areas identified as historic or
archaeological resources.
Yes
Archaeological resources were identified at the Tutu Park
Shopping Center. Remedial activities are not anticipated to
further impact archaeological resources in this area.
CFR 
Code of Federal Regulations.
USC 
United States Code.
USEPA 
United States Environmental Protection Agency.
E.O. 
Executive Order.
K3
H"
01
g:\aprojoct\tutu\prO013.037\data\FLSARAR.XLS
GERAGHTY & MILLER, INC.
Table 3-3. Summary of Potential Federal Action-Specific Applicable or Relevant and Appropriate Requirements, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Requirement
Applicable or Relevant
and Appropriate
Requirements
Comments
Clean Air Act
40 CFR Part 61
Establishes primary and secondary standards
for air emissions.
Yes
Remedial activities under consideration will discharge
off-gas to the air (i.e., air stripping).
General Pretreatment Regulations
40 CFR 403.5 and Local POTW Regulations
Establishes pretreatment standards for
discharge of pollutants into a POTW.
Yes
Remedial activities under consideration may involve discharge
to a POTW.
RCRA Land Disposal Restrictions
40 CFR 268 (Subparts C and D)
C
Land disposal restrictions for movement of
excavated material.
Yes
Remedial activities under consideration may require
excavation and disposal of contaminated soil.
o
Nj
CFR 
Code of Federal Regulations.
POTW 
Publicly Owned Treatment Works.
RCRA 
Resource Conservation and Recovery Act
GERAGHTY & MILLER, INC
O
Table 3-4.
Summary of Potential Federal Chemical-Specific Applicable or Relevant and Appropriate Requirements and To-Be-Considered
Material, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Requirement
Applicable or
Relevant and
Appropriate Requirements
and To-Be-Considered Material
Comments
Federal Safe Drinking Water Act
40 CFR 141; 40 CFR 143
Establishes MCLs for drinking water.
Yes
Remedial activities under consideration may provide potable
water to residents and commercial users.
Federal Surface Water Quality Standards
40CFR 131
Establishes MCLs for discharge to surface water.
Federal Ambient Air Quality Standards
40 CFR Part 61; 40 CFR Section 52.21
Establishes primary and secondary air
quality standards.
Yes
Yes
Remedial activities under consideration may involve discharge
to surface water (Turpentine Run).
Remedial activities may involve emissions to ambient air.
H
C
H
o
xf
H-
i>
USEPA's Vadose Zone Model - To-Be-Considered Material
Soil Cleanup Concentration
Proposes guidance levels to evaluate potential impacts
to ground water quality from constituents in soil.
Yes
Constituents detected in soil at investigated properties will be
compared to soil screening levels as remedial action levels to
determine if remediation is potentially warranted and will be
used to develop remediation goals (CDM Federal
Programs Corporation 1995b).
CFR 
Code of Federal Regulations.
MCLs 
Maximum Contaminant Level.
USEPA 
United States Environmental Protection Agency.
GERAGHTY & MILLER, INC.
r;o
Table 3-5. 
Summary of Potential U.S. Virgin Islands Location-Specific Applicable or Relevant and Appropriate Requirements, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Requirement
Applicable or
Relevant and
Appropriate Requirements
Comments
Water Resources Conservation
VIC, Title 12, Chapter 5, Sections 151 and 153
Water conservation required to protect natural resources.
Requires a permit for well installation or changes.
Yes
Remedial activities under consideration may require
the installation of extraction wells.
Environmental Protection
VIC, Title 12, Chapter 13, Section 533
Requires an "earth change plan" before land is
cleared, graded, filled, or otherwise disturbed.
Yes
Portions of the Tutu Wells Site may require capping,
regrading, or excavation to implement remedial
activities.
Coastal Zone Management
VIC, Title 12, Chapter 21, Section 903
Limits activities with the U.S. Virgin Islands
Coastal Zone to protect marine resources.
No
The Tutu Wells Site is not within an area designated a
coastal zone.
VIC
Virgin Islands Environmental Code (USVI/DCCA 1979).
en
•••-i
G:\APROJECT\TUTU\PR0013.037\DATAWILSARAR.XLS
GERAGHTY & MILLER, INC.
O
Table 3-6. 
Summary of Potential U.S. Virgin Islands Action-Specific Applicable or Relevant and Appropriate Requirements, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Requirement
Applicable or
Relevant and
Appropriate Requirements
Comments
Water Pollution Control
VIC, Title 12, Chapter 7, Sub-Section 184, Division 3
Requires any person proposing to commence
a discharge of pollutants to complete a TPDES
application.
Yes
Discharge of treated groundwater to the Turpentine Run
may be considered.
Air Pollution Control
VIC, Title 12, Chapter 9, Section 206-20
Requires permitting of controlled air discharges
to atmosphere.
Sewaoe Disposal
VIC, Title 19, Chapter 55, Section 1522-4
Regulates waste that may be disposed to a
sanitary sewer.
Yes
Yes
Equipment related to remedial action will emit
air pollutants.
Remedial activities under consideration will
discharge off-gas to the air (i.e., air stripping).
A potential discharge option is to the local POTW.
H
i—
*—
Oo
••-J
Water Resources Conservation
VIC, Title 12, Chapter 5, Sections 151, 155, 156, 159
Requires a permit for withdrawal of water in excess
of 500 gpd (regulates groundwater pumpage).
Yes
Remedial activities under consideration may involve
withdrawal of groundwater in excess of 500 gpd.
VIC 
Virgin Islands Environmental Code.
TPDES 
Territorial Pollution Discharge Elimination System.
POTW 
Publicly owned treatment works.
gpd 
Gallons per day.
GERAGHTY & MILLER. INC.
—i
Table 3-7. 
Summary of Potential U.S. Virgin Islands Chemical-Specific Applicable or Relevant and Appropriate Requirements, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Requirement
Applicable or
Relevant and
Appropriate Requirements
Comments
Drinking Water Standards
VIC, Title 19, Chapter 51, Section 1303-16
Establishes maximum contaminant levels for
drinking water supplies.
Yes
Remedial activities under consideration may provide
potable water to residents and commercial users.
VIC
Virgin Islands Environmental Code.
-0
g:\aproject\tutu\pr0013.037\data\VICSARAR.XLS
GERAGHTY & Mil ,LER, INC.
o
Page 1 of 9
Table 3-8. 
Summary of Analytes Detected in Groundwater Above Remedial Action Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Parameter
Volatile Organic Compounds
Vinyl chloride
1 , 2-Dichloroethene(total) *
1 ,2-Dichloroethane
Trichloroethene
RAU 
Well
(ug/L) 
Designation
2 
MW-3
MW-15
MW-16
TT-3D
TT-5
100 
CHT-7D
DW-1
La Place**
MW-1
MW-1D
MW-3
MW-4
MW-6D
MW-7
MW-8
MW-10
MW-10D
MW-15
MW-16
Steele**
Tillett
TT-2
TT-2FR
TT-3D
TT-5
5 
TT-1
5 
MW-1
MW-1D
MW-3
MW-4
MW-6D
MW-7
MW-8
MW-10
MW-10D
MW-12D
MW-15
MW-16
MW-1 7
MW-21D
OHMW-4
Smith
Tillett
TT-2
TT-2FR
TT-3D
Concentration
(ug/L)
5/94 
6/94
48
260 D
1 300
9 J
42
91
92 J
95
950 D
500
440 D
-- 
76 J
100
180
88 J
76 J
110J
1 500 D
2100
100
360 D
330
330
280
180
290
78
71
17 J
6 J
11
27
10 J
1 8 J
14 J
9 J 
-
23
72 J
9 J
14 J
16
19 J
45
20 J
20J
15 J
7/94
„
-
-
-
-
„
-
-
-
-
-
-
-
-
-
-
-
-
-
--
--
-
-
-
-
--
_
-
--
-
--
-
-
—
—
-
-
--
—
-
-
'
-
-
-
—
See last page for footnotes.
G:\APROJECT\TUTU\PRO013.037\DATA\MCL.XLS
GERAGHTY & MILLER, INC.
TUT 
OO7 216O
Page 2 of 9
Table 3-8. 
Summary of Analytes Detected in Groundwater Above Remedial Action Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
RAL 
Well
Parameter 
(ug/L) 
Designation
Volatile Organic Compounds (continued)
Benzene 
5 
CHT-3
KFC-1
MW-5
MW-7
SW-2
SW-3
SW-7
SW-7 FR
TT-1
TT-1D
TT-4
Tetrachloroethene 
5 
CHT-6D
CHT-7D
Delegarde
DW-1
DW-2
MW-1
MW-1D
MW-3
MW-4
MW-4D
MW-6D
MW-6R
MW-7
MW-8
MW-10
MW-10D
MW-12D
MW-1 3D
MW-1 5
MW-1 6
MW-1 7
MW-20D
MW-21D
MW-25
OHMW-1
OHMW-2
OHMW-3
OHMW-4
Ramsay
Smith
SW-4
Concentration
(ug/L)
5/94 
6/94
1700
110J
460 DJ
21
550 J
10000J
99 J
110J
21 000 D
1700D
21000
12
36
15 J
42 J
18
330 D
360
56
20 J
17 J
31
10
130
38 J
34 J
48 J 
———
33 J
28 J
120
71 J
37
22 J
-- 
45 J
11
10
26
6 J
140
11
110J
15 J
7/94
„
-
-
-
-
—
—
-
-
-
-
_
—
-
—
-
-
-
—
-
—
-
-
-
—
—
—
..
-
—
—
—
--
-
-
—
—
—
-
-
-
—
See last page for footnotes.
G:\APROJECT\TUTU\PR0013.037\DATA\MCL.XLS
GERAGHTY & MILLER, INC.
TUT 
O07 2161
Page 3 of 9
Table 3-8. 
Summary of Analytes Detected in Groundwater Above Remedial Action Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
RAL
Parameter 
(ug/L)
Volatile Organic Compounds (continued)
Tetrachloroethene (continued) 
5
Toluene 
1 000
Ethylbenzene 
700
Xylenes (total) 
10000
Inorganic Compounds/A nalytes
Aluminum 
50 to 200
Well
Designation
Tillett
TT-2
TT-3
TT-3D
SW-3
TT-1
TT-4
CHT-3
MW-5
SW-3
TT-1
TT-4
SW-3
TT-1
Four Winds II FR»*
Harvey**
CHT-7D
Delegarde
Gassett**
MW-1
MW-6R
MW-7
MW-8
MW-9S
MW-10
MW-10D
MW-1 ID
MW-12D
MW-1 5
MW-1 7
MW-24
MW-25
OH MW-1
OHMW-2
OHMW-3
OHMW-4
Smith
SW-5
SW-6
5/94
180
-
-
-
__
-
-
—
-
-
—
-
„
-
_
-
-
1890 B
154 B
-
-
-
-
2050
956
160B
147 B
93.9
-
-
-
-
245000
8970
60000
356000
60.9 B
12100
14500
Concentration
(ug/L)
6/94
—
90
91
23
3200 J
1 6000 D
17000
1800 D
760 DJ
4100 J
3700 D
3300 J
22000 J
1 8000 D
_
-
118B
-
--
1 8600 J
46400
10300
28700
-
-
-
-
-
3730 J
33000 J
41 60
15800
-
-.
—
-
-
-
--
7/94
„
—
-
--
__
--
-
—
--
--
—
--
..
--
63.1 B
111 B
-
--
-
-
-
--
--
-
-
-
-
-
-
-
-
—
—
-
—
-
-
-
—
See last page for footnotes.
G:\APROJECT\TUTU\PR0013.037\DATA\MCL.XLS
GERAGHTY & MILLER, INC.
TUT 
OO7
»162
Page 4 of 9
Table 3-8. 
Summary of Analytes Detected in Groundwater Above Remedial Action Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
RAL
Parameter 
(ug/L)
Inorganic Compounds/Analvtes (continued)
Aluminum (continued) 
50 to 200
Antimony 
6
Arsenic 
50
Barium 
2000
Beryllium 
4
Chromium 
1 00
Well
Designation
TT-1
TT-1D
TT-2
TT-5
DW-1
DW-2
Four Winds II «*
KFC-1
MW-1
MW-2
MW-3
MW-4
MW-5
MW-6D
MW-7
MW-1 3D
MW-1 8
MW-21D
MW-22D
OHMW-1
OHMW-3
SW-2
SW-3
SW-7
SW-7FR
TT-1
TT-3D
VIHA 1 **
OHMW-2
MW-1 3D
OHMW-4
MW-1 3D
DW-2
MW-1
MW-2
MW-6R
MW-7
MW-8
MW-1 3D
MW-1 7
OHMW-1
OHMW-3
OHMW-4
5/94
__
—
-
-
-
1490
—
-
• -
-
-
-
-
-
-
-
-
-
-
16.1 B
50.7 B
-
-
—
—
-
-
-
80.8
„
4320
-
628
-
-
-
-
-
-
-
2200
4610
397
Concentration
(ug/L)
6/94
6130 J
153 B
1090 J
787 J
300
-
„
18.6 BJ
17.6 B
15B
17B
20.1 B
20.1 B
25.3 B
21.3 B
424 B
20.6 
B
19.6 B
22.3 
BJ
—
—
15.4BJ
16.4BJ
19.2 BJ
17.6 BJ
19.7 
B
19 B
-
-
4400 B
-
40.8 
B
_
453
619
203
1050
210
4300
238
—
-
—
7/94
__
-
-
-
-
-
22 B
-
-
-
--
-
-
--
-
-
-
—
-
—
-
-
-
-
-
-
20.6 B
-
._
-
-
_
-
-
-
--
-
-
-
-
-
—
See last page for footnotes.
G:\APROJECTVTUTU\PRO013.037\DATA\MCL.XLS
GERAGHTY & MILLER, INC.
TUT 
007 2163
Page 5 of 9
Table 3-8. 
Summary of Analvtes Detected in Groundwater Above Remedial Action Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
RAL 
Well
Parameter 
(ug/L) 
Designation
Inorganic Compounds/Analvtes (continued)
Copper 
TT 
MW-13D
OHMW-4
Iron 
300 
Delegarde
DW-1
Gassett**
Harvey**
DW-2
KFC-1
MW-1
MW-1D
MW-2
MW-3
MW-4
MW-4D
MW-5
MW-6R
MW-7
MW-8
MW-9S
MW-10
MW-10D
MW-11D
MW-12D
MW-1 3
MW-1 3D
MW-1 5
MW-1 7
MW-1 8
MW-1 9
MW-20
MW-20D
MW-21D
MW-24
MW-25
OHMW-1
OHMW-2
OHMW-3
OHMW-4
SW-2
SW-3
SW-4
SW-5
SW-6
SW-7
Tillett
TT-1
TT-1D
TT-2
TT-5
5/94
-
1370
41 20 J
-
300
-
-
—
-
-
-
-
-
-
-
-
-
-
3760
1410
607
323
334
—
—
-
-
-
--
-
-
-
-
-
338000
15700
1 54000
572000
-
-
-
18600
20300 J
-
530
-
-
-
.
Concentration
(ug/L)
6/94
1730 J
-
„
1150
-
-
3100
80000 J
25600
10500
19900
3830
7590
1440
5730
56900
44800
49700
-
—
-
,
-
3670
378000
5360
43500
68500 J
3420 J
23900
37800
19400
6890
30500
-
—
-
—
14100 
J
108000 J
5140
-
—
1 4800 J
-
7810
515
2320
1130
7/94
-
-
—
-
-
2500
-
-
-
-
—
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
—
-
-
-
-
-
-
-
-
-
-
'
-
-
—
-
—
-
-
-
-
—
—
See last page for footnotes.
G:\APROJECT\TUTU\PR0013.037\DATA\MCl.XLS
GERAGHTY & MILLER, INC.
TUT 
OO7 2164
Page 6 of 9
Table 3-8. 
Summary of Analytes Detected in Groundwater Above Remedial Action Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
RAL 
Well
Parameter 
(ug/L) 
Designation
Inorganic Compounds/Analvtes (continued)
Lead 
TT 
Gassett
MW-1
MW-9S
MW-1 8
MW-20
MW-20D
OHMW-1
OHMW-2
OHMW-3
OHMW-4
SW-3
SW-7
SW-7FR
Manganese 
50 
CHT-7D
Delegarde
Four Winds II » *
Four Winds II FR*"
Harvey*"
DW-2
KFC-1
MW-1
MW-1D
MW-2
MW-3
MW-4
MW-4D
MW-5
MW-6R
MW-7
MW-8
MW-9S
MW-10
MW-10D
MW-12D
MW-1 3
MW-1 3D
MW-1 5
MW-1 6
MW-1 7
MW-1 8
MW-1 9
MW-20
MW-20D
MW-21D
MW-24
MW-25
5/94
167
-
53.7
-
-
-
48.3
201
17.3
71.8-
-
-
—
163 B
-
267
620
-
-
--
-
-
-
-
-
--
—
—
2560
597
216
114
-
.
—
—
—
-
-
-
-
-
-
—
Concentration
(ug/L)
6/94
—
27.1 J
—
27.4
16
20
-
-
-
-
143
70.8
93.8 J
282
-
-
-
-
-
1030 J
570
338
366
2540
1290
55.1
1080
736
453
2350
-
-
-
—
110
20400
149
532
1550
3740 J
72.6 J
997
1140
402
215
982
7/94
—
-
-
-
-
—
-
-
-
-
-
-
--
..
-
125
119
-
-
-
-
-
-
-
-
-
-
-
—
-
-
-
-
—
—
—
-
-
-
--
-
-
-
-
-
—
See last page for footnotes.
G:\APROJECT\TUTU\PR0013.037\OATA\MCL.XLS
GERAGHTY & MILLER, INC.
TUT 
OO7
Page 7 of 9
Table 3-8. 
Summary of Analytes Detected in Groundwater Above Remedial Action Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
RAL
Parameter 
(ug/L)
Inorganic Compounds/Analvtes (continued)
Manganese (continued) 
50
Mercury 
2
Nickel 
100
Thallium 
2
Chloride 
250,000
Total Dissolved Solids 
500,000
Well
Designation
OHMW-1
OHMW-3
OHMW-4
SW-2
SW-3
TT-1
TT-1D
TT-2
TT-4
TT-5
OHMW-1
MW-4D
DW-2
MW-1
MW-2
MW-6R
MW-7
MW-8
MW-10D
MW-1 3D
MW-1 7
OHMW-1
OHMW-3
OHMW-4
DW-1
MW-24
Eglinl*"
Eglin III"
Harvey**
Matthias**
MW-21D
OHMW-1
OHMW-2
OHMW-3
Smith
SW-5
CHT-3
CHT-6D
CHT-7D
Delegarde
DW-1
DW-2
Eglin I"*
Eglin III"*
5/94
5870
3180
13500
-
-
—
—
-
-
-
3.1
„
374
-
-
-
—
189
--
—
1120 J
1840 J
603 J
__
-
269
368
.
294
-
354
332
351
335
378
_
—
-
1440
-
-
1180
1330
Concentration
(ug/L)
6/94
-
-
—
943 J
6340 J
1710
1880
1220
957
1110
-
460
-
124
266
127
445
-
2050
140
-
-
-
2.4 B
2.1 B
..
-
-
-
402
-
-
-
.
1320
850
870
-
910
870
.
--
7/94
—
--
-
-
-
-
-
-
-
--
--
„
-
-
-
-
-
-
-
-
-
-
—
--
_
--
_.
--
1700-
-
-
-
-
-
--
_
—
-
-
-
-
--
—
See last page for footnotes.
G:\APROJECTVTUTU\PR0013.037\DATA\MCL.XLS
GERAGHTY & MILLER, INC.
TUT 
007 
2166
Page 8 of 9
/—\
Table 3-8. 
Summary of Analytes Detected in Groundwater Above Remedial Action Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
RAL 
Well
Parameter 
(ug/L) 
Designation
Inorganic Compounds/Analvtes (continued)
Total Dissolved Solids (continued) 
500,000 
Four Windsl**
Gassett**
Harthman Race Track
Harvey**
KFC-1
La Place*'
Matthias**
MW-1
MW-1D
MW-2
MW-3
MW-4
MW-4D
MW-5
MW-6D
MW-6R
MW-7
MW-8
MW-9S
MW-10
MW-12D
MW-1 3
MW-1 3D
MW-1 5
MW-1 7
MW-1 8
MW-1 9
MW-20
MW-20D
MW-21D
MW-22D
MW-24
MW-25
OHMW-1
OHMW-2
OHMW-3
OHMW-4
Ramsay
Smith
SW-5
Nitrate (as N) (mg/L) 
10,000 
Gassett*"
Harthman
Race Track
MW-1
MW-2
MW-1 3
MW-1 7
MW-24
Ramsay
5/94
_
700
1100
~
-
1360
-
-
-
-
-
-
-
-
-
-
-
830
790
640
-
-
-
-
-
-
—
-
-
-
--
-
354
1110
1290
1040
870
335
378
11.3
13.6
-
-
-
-
-
10
Concentration
(ug/L)
6/94
__
-
-
-
1070
-
920
880
910
900
920
1180
810
840
910
760
920
'—
-
-
900
1520
990
870
800
1040
500
780
2260
1890
940
950
-
-
-
-
-
-
.
„
—
12.4
15.9
10.6
22.7
13.3
—
7/94
1240
--
—
1190
-
-
-
-
-
--
-
-
-
-
-
-
-
-
--
-
-
-
—
-
-
--
-
-
-
-
-
-
-
-
-
-
--
-
--
„
—
--
-
-
-
--
—
See last page for footnotes.
G:\APROJECT\TUTU\PR0013.037\DATA\MCL.XLS
GERAGHTY & MILLER, INC.
TUT 
007 
2167 o
Page 9 of 9
Table 3-8. 
Summary of Analytes Detected in Groundwater Above Remedial Action Levels at the Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
* 
Analytical results reported for total isomers (cis- and trans-) for 1,2-dichloroethene (1,2-DCE); RAL is
for trans- isomer.
** 
Sample results were not validated.
Not available.
mg/L 
Milligrams per liter.
ug/L 
Micrograms per liter.
B 
The reported value was obtained from a reading that was less than the Contract Required Detection Limit (CRDL),
but greater than or equal to the Instrument Detection Limit (IDL).
J 
Estimated value.
D 
Compound concentration was determined at a secondary dilution factor.
RAL 
Remedial Action Level.
TT 
Treatment technique. (Action Levels: Copper 1,300 ug/L, lead 15 ug/L). Values in parentheses are
determined by the USEPA.
USEPA 
U.S. Environmental Protection Agency.
Note: 
RALs derived from Federal Drinking Water Standards.
G:\APROJECTVTUTU\PR0013.037\DATA\MCL.XLS
GERAGHTY & MILLER, INC.
TUT 
007 
2.1&8
Table 4-1. Development and Screening of Technologies for Soil, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Page 1 of 2
General Response Action
Remedial Technology
Process Options
Description
Screening Comments
No Action
Institutional Controls
Containment
Treatment
None
Access restrictions
Capping
In-situ
Not applicable
Deed restrictions
Capping
Soil vapor extraction
(SVE)
Bioventing
No action.
Restrictions on
property by limiting
access and use of
areas of
contamination.
Installation of
low-permeable
barrier over areas of
contamination.
Vacuum (extraction)
wells that pull air
from the soil to
facilitate the removal
of VOCs.
Extraction and/or
injection of air in soils
to enhance biological
degradation of BTEX
and non-halogenated
VOCs, and semi-VOCs.
Required for
consideration by NCP
(comparison with other
alternatives).
Potentially applicable.
Potentially applicable.
Potentially applicable.
Potentially
applicable
with only non-
halogenated VOCs.
o
See last page for footnotes.
Ki
H-
i>
"0
GERAGHTY & MILLER, INC.
Table 4-1. Development and Screening of Technologies for Soil, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Page 2 of 2
General Response Action
Remedial Technology
Process Options
Description
Screening Comments
Removal
Excavation
Ex-situ Treatment
Excavation and
disposal
Biopile/SVE
(hSitieration
Removal and
disposal of
contaminated soil.
Excavated soils are
stockpiled and mixed
with nutrients and/or
oxygen to enhance
biodegradation.
of f
 :-
the il;r;e|tie|:!;$^j.is^|^ri;;;bi;.;:;:;
•diJSj:^!^
as backfill; ^^.A^M^
Soils are
and expps^I jt<> :
extrernely JiigiB
temperatures to
volatilize vlGs.
lnCirteratibrV:rt|ay
place bri-site or ^ off -site ^
Potentially applicable.
Potentially applicable.
Kia bei cbst
bhibitive.
NCP 
National Contingency Plan.
VOCs 
Volatile organic compounds.
BTEX 
Benzene, toluene, ethylbenzene, and xylene.
SVE 
Soil vapor extraction.
II 
Option not retained for further analysis.
GERAGHTY & MILLER, INC
Table 4-2. 
Off-Gas Treatment Technology Evaluation, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Technology
Advantages
Disadvantages
Thermal Oxidation (Thermox)
High removal efficiencies (>99%)
Low capital cost
Low sensitivity to process condition changes
Can process up to 70% LEL
Effective in chlorinated solvent destruction
Enables faster remediation
High operating T (> 1,400°F)
High insulation maintenance
High metal fatigue due to high T
May be limited to processing <25% LEL in future
High fuel consumption
Fire codes may make permitting difficult
Catalytic Oxidation
Low operating T « 1 ,250°F)
Relatively safe-operates below 25% LEL
No NOx formation
Very low fuel costs
Stainless steel interior
Very little metal fatigue
Effective heat recovery
High destruction effectiveness with additional catalyst
High capital cost
Risk of catalyst poisoning/deactivation
Reduced catalyst activity after 5 years
Extends remediation time for highly-contaminated sites
Need larger unit at high concentration due to dilution air
Vapor Phase Granular Activated
Carbon (VPGAC)
Effective at low mass flows
No external fuel requirements
Easy to permit
High removal efficiencies
Very high cost at moderate/high mass flows
Must maintain inlet stream <50% relative humidity
Potential future liability from carbon disposal sites
Transfers contaminate from vapor to solid - not destroyed
Minimal effect on MTBE
Sensitive to process condition changes
Limited to < 25% LEL
Desorbed by high blower outlet T/high heat of adsorption
—1c
-~!
M
j_t
-•J
> 
Less than.
LEL 
Lower explosive limit.
% 
Percent.
F 
Farenheit.
NOx 
Nitrogen oxide(s).
T 
Temperature.
MTBE 
Methyl tertiary butyl ether.
OERAOHTY 8 MILLER, INC
O
Page 1 of 4
Table 4-3. 
Development and Screening of Technologies for Groundwater, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
General Response
Action
Remedial Technology
Process Options
Description
Screening Comments
No Action
Institutional Controls
None
Access restrictions
Not available
Deed restrictions
No action.
Deeds for property in the area
would include restrictions on
wells.
Required for consideration by
NCP (comparison with other
alternatives).
Potentially applicable.
Alternative water supply 
Public water supply
Extension of existing water
system to serve residences in
contaminated plumes.
Potentially applicable.
Trucking water
Delivery of potable water to
serve residences.
Potentially applicable.
;ii^|!|^P^i|!|i|^||||;il|||PI
expense arid administrative
difficultfes associated with
constructibn of distiributidn piping.
Collection/Containment 
Extraction
Extraction wells
Series of recovery wells to
extract contaminated
groundwater.
Potentially applicable.
c
H
O
W
h*
Nl
M
Subsurface trains
Not applicable due to shallow
See last page for footnotes.
GERAGHTY & MILLER, INC.
O
Page 2 of 4
Table 4-3. 
Development and Screening of Technologies for Groundwater, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
General Response
Action
Remedial Technology
Process Options
Description
Screening Comments
Collection/Containment 
;|pi|;||jj||||
(continued) 
118111111
Enhanced groundwater
recovery
Bedrock fracturing
Treatment
In-situ
Vacuum enhance^
Air sparging
Biosparging
diameter and shallower depths^
^^
Enhanced recovery of
contaminated water through the
detonation of explosives in the
saturated zone.
Enhanced recovery ; of
cbhtarriinateidlv^ater through
application i of vacuum at
V extraction >ivells ;>:
 
:i- • "• ;
 : •;'.;•.;• ••: •:•• .:."' '•" :
Injection of air into saturated
zone to strip VOCs from
groundwater.
Not alpplicabl^ due to
Not iriiplementabte in bedrock;
Potentially applicable in
non-residential and/or open
areas.
Not applicable;: liirnitatibhs due to
anisotrppic becirQck conditions.
Potentially applicable.
Injection of small amounts of air
into the saturated zone
to enhance the natural aerobic
biodegradation of VOCs. The
stripped VOCs are captured by
an SVE system for further processing.
Potentially applicable (properties
with non-halogenated VOCs).
See last page for footnotes.
TUT 
007 
2173
GERAGHTY & MILLER, INC.
Page 3 of 4
Table 4-3. 
Development and Screening of Technologies for Groundwater, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
General Response
Action
Remedial Technology
Process Options
Description
Screening Comments
Treatment (continued)
Ex-situ
Natural remediation
Air stripping
Granular activated
carbon (GAC)
Filtration
Precipitation, floccu-
lation, sedimentation
Reverse osmosis
Ion exchange
UV oxidation/
reduction
GAC fluidized bed
system
Attenuation and
degradation
Mixing large volumes of air with
water in a packed column to
promote transfer of VOCs to air.
Adsorption ot contaminants
onto activated carbon by
passing water through carbon.
Not cost effective at removing vinyl
chloride.
Filtering to remove solids.
Processes for the removal of
metals and solids.
Membrane diffusion to remove
metals and solids.
Ionic species removal for metal.
Redox reactions for organic
removal.
Combines fluidized bed
technology with GAC.
Reduction of constituent con-
centrations through natural
attenuation/degradation.
See last page for footnotes.
TUT 
007 2174
Potentially applicable.
Potentially applicable.
Potentially applicable.
Potentially applicable.
Potentially applicable.
Potentially applicable.
Potentially applicable.
Potentially applicable.
Potentially applicable.
GERAGHTY & MILLFR, INC
Table 4-3. 
Development and Screening of Technologies for Groundwater, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Page 4 of 4
General Response
Action
Remedial Technology
Process Options
Description
Screening Comments
Discharge
Off-site discharge
Discharge to surface
water
Treated groundwater discharged
to Turpentine Run.
Potentially applicable; permitting-
dependent.
Not applicable; difficulties du^ to
Treated groundwater used for
Br$^^
^
- implementability issues and high
POTW 
Publicly owned treatment works.
USVI-pPW 
U.S. Virgin Islands - Department of Public Works.
Eliminated from further consideration in preliminary screening.
NCP 
National Contingency Plan.
VOC 
Volatile organic compound.
O&M 
Operation and maintenance.
SVE 
Soil vapor extraction.
GAC 
Granular activated carbon.,
UV 
Ultraviolet.
RCRA 
Resource Conservation and Recovery Act.
TSDF 
Treatment, storage and/or disposal facility.
TUT 
007 
21.75
GERAGHTY & MILLER, INC.
Table 4-4. 
Summary of Influent Concentrations and Maximum Contaminant Levels, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Parameters
GRA2
Source Containment Wells
Total 
Dissolved
Concentration 
Concentration
GRA3
Plume Containment Wells
Total 
Dissolved
Concentration 
Concentration
GRA4
Source and Plume Containment Wells
Total 
Dissolved
Concentration 
Concentration •
Background
Water Quality
Inorganics
Turpentine Run<9>
Maximum
Contaminant
Level
Organic Constituents (uo/L) (1)
Tetrachloroethene (PCE) 
4970.00
Trichloroethene (TCE) 
40.00
1,2-Dichloroethene (1,2-DCE) 
360.00
NA
NA
NA
85.00
16.00
49.00
NA
NA
NA
2770.00
30.00
220.00
NA
NA
NA
5.OO
5.00
0.1 «
Inorganic Constituents (mg/L)
Iron 
105.00
Magnesium 
55.00
Manganese 
1.50
Potassium 
4.00
Sodium 
280.00
Calcium 
76.00
Hardness as CaCO3 
NA
Chloride 
180.00
Total Dissolved Solids (TDS) 
NA
NO
50.00
0.140
4.00
290.00
72.00
395 m
NA
1100.00
0.15
33.00
0.05
5.00
336.00
37.OO
NA
245.00
NA
NO
36.00
0.050
6.00
370.00
39.00
230.00
NA
1260.00
205.00
115.00
5.00
45.00
289.00
90.00
NA
207.00
NA
0.18
38.00
0.034
5.00
314.00
47.00
310 (2)
NA
1115.00
0.0
77
519.00
30.0
392.0
440.0
1,700
0.30
0.05
250 CT
500 Hl
Recovery wells within catchment area include Recovery Well RW-1 (which is near existing Monitoring Well MW-12D), Recovery Wells RW-2 and RW-3 (which are near the
Smith and Matthias Supply Wells), Recovery Well RW-4 (which is near Monitoring Well OHMW-4), and Recovery Well RW-5 (which is near monitoring well cluster
MW-1 /MW-1 D). Data related to proposed Recovery Well RW-4 included historic water quality data from the Harvey Supply well. These data indicate a past PCE
concentration at 7,600 parts per billion (ppb) or ug/L. Total/dissolved concentrations are based upon sample data collected from associated monitoring wells.
in
(2)
13)
(41
(5)
GRA
NA
NO
ug/L
mg/L
Data refer to concentrations of individual volatile organic compound (VOC) constituents identified in groundwater samples.
Hardness is a quantification of water quality as indicative of the presence of calcium carbonate (CaCO3).
Value refers to Secondary Maximum Contaminant Levels.
Value represents trans- isomer of 1,2-dichloroethene.
Sodium and potassium were combined in reference document191.
Water quality data taken from reference entitled "Water Records of U.S. Virgin Islands 1962-1969." Sample was recorded at the
Mt. Zion Gauging Station on July 22, 1964 (U.S. Geological Survey 1973).
Groundwater remedial alternative.
Not applicable.
Not detected above sample qualification limit.
Not available.
Micrograms per liter.
Milligrams per liter.
TUT 
007
1176
GERAGHTY & MILLER, INC
o
Table 4-5. Summary of Estimated Impacted Soil Volumes, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Estimated Area of Depth to Bottom 
Thickness 
Volume of soils 
Volume of Soils
Property 
Constituents of 
Impacted Soils 
of Impacted Soils 
Previously Remediated 
Requiring Excavation
Concern
(area, ft2) 
(feet) 
(feet) 
(cubic yards) 
(cubic yards)
Curriculum Center 
BTEX, and 1,1,1 -TC A
Ramsay Motors 
Benzene and ethylbenzene
Texaco Tutu Service Station Benzene and ethylbenzene
Tillett Gardens 
Manganese and PCBs
Esso Tutu Service Station 
PCE, 1,1 -DCA, 1,2-DCE,
BTEX
Western Auto 
Benzene, toluene, and
xylene
O 'Henry Dry Cleaners 
PCE
ft2 
Square feet.
[Al
IB]
240 
0.5
40'41
200
25 «)
26(6)
2g0 18)
2518'
BO
171
190(8)
200(8)
150
440
460'91
400
(1) 
Soil removed during previous tank removals as part of early removal actions prior to
(2) 
In some instances soil volumes that need to be excavated
5
5
4
2
9
8
12
9
9
6
7
2
8
FS.
may Include soils that do not require
[CJ
0.5
4
5
2
2
9
1
4
0
0
6
7
2
8
remediation or that
(1)
[D]
0
0
0
0
0
20
0
0
63
67
10
25
0
0
Total
KAxB)/27]
5
gO)
37
4
2
97
7
22
0
0
33
114
34
119
482
Soil Volume
Currently
Requiring
Remediation
(cubic yards)
(2)
t(AxC)/27-D)
5
6
37
2
2
77
1
8
0
0
23
89
34
119
403
were previously remediated. Therefore, soil volumes requiring excavation may be different from those requiring remediation.
(3) 
Includes volume of existing underground storage tank.
(4) 
Estimated area based on area of impacted soils defined on Figure 4-2.
(5) 
Area around individual impacted soil samples is assumed to be 5' x 5'.
(6) 
Near north oil/water separator at Esso.
(7) 
Includes soil samples B-101 and B-102 (see previous note5).
(8) 
Assumes impacted soil removed with installation of new underground storage tanks prior to FS
(9) 
Includes the 4-inch PVC pipe area at Four Winds Plaza near Western Auto.
BTEX 
Benzene, toluene, ethylbenzene, and xylene.
PCE 
Tetrachloroethene.
1,1 -DCA 
1,1-Dichloroethane.
1 ,2-DCE 
1 ,2-Dichloroethene(clsArans).
1,1,1-TCA 
1,1,1-Trichtoroethane.
PCBs 
Polychlorinated biphenyls.
r,PR AOHTY £? MII I FR INC
O
Q
Ki
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Table 4-6. 
Evaluation of No Action/Institutional Controls Technologies Option on Property-Specific Basis, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Properties
Description
Effectiveness
Implementability
Cost 
Screening Comments
Curriculum Center
Ramsay Motors
Texaco Tutu
Service Station
Tillett Gardens
Deed restrictions for soil and
bedrock excavation and
groundwater use.
Deed restrictions for soil
excavation and groundwater use.
Deed restrictions for soil
excavation and groundwater use.
Deed restrictions for soil
excavation and groundwater use.
Some natural degradation would
occur, but most of the contaminants
volume would not be reduced.
Limited effectiveness.
Some natural degradation would
occur; may be effective due to the
comparatively low COC
concentrations.
Some natural degradation would
occur, but most of the contaminants
volume would not be reduced.
Limited effectiveness.
Contaminant volume would not
be significantly reduced. Limited
effectiveness.
Easily implemented.
Easily implemented.
Easily implemented.
Easily implemented.
Low 
Retained.
- Provides comparison for other options.
- Required by NCP.
Low 
Retained.
- Provides comparison for other options.
- Required by NCP.
Low 
Retained.
- Provides comparison for other options.
- Required by NCP.
Low 
Retained.
- Provides comparison for other options.
- Required by NCP.
Western Auto 
Deed restrictions for soil
excavation and groundwater use.
Esso Tutu 
Deed restrictions for soil
Service Station 
excavation and groundwater use.
Some natural degradation would
occur, but most of the contaminant
volume would not be reduced.
Limited effectiveness.
Some natural degradation would
occur, but most of the contaminant
volume would not be reduced.
Limited effectiveness.
Easily implemented.
Easily implemented.
Low 
Retained.
- Provides comparison for other options.
- Required by NCP.
Low 
Retained.
- Provides comparison for other options.
- Required by NCP.
c
O'Henry 
Deed restrictions for soil and
Dry Cleaners 
bedrock excavation and
groundwater use.
Some natural degradation would
occur, but most of the contaminant
volume would not be reduced.
Limited effectiveness.
Easily implemented.
Low 
Retained.
- Provides comparison for other options.
- Required by NCP.
NCP 
National contingency plan.
COC 
Constituents of concern.
GERAGHTY & MILLER, INC.
Table 4-7. 
Evaluation of Capping Technology Option on Property-Specific Basis, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Properties
Description
Effectiveness
Implementability
Cost 
Screening Comments
Curriculum Center
Install asphalt paving over
impacted soil to reduce
infiltration.
Effective
Easily implemented.
Low 
Retained.
- Capping can be effective in reducing
infiltration; easily implemented.
Ramsay Motors
Remove and replace cracked
concrete floor slab in
maintenance garage.
Effective
Easily implemented. 
Low
Retained.
- Capping can be effective in reducing
infiltration; easily implemented.
Texaco Tutu
Service Station
Inspect and maintain existing
concrete paving and replace if
necessary.
Effective
Easily implemented.
Low 
Retained.
- Capping can be effective in reducing
infiltration; easily implemented.
Tillett Gardens
Install asphalt paving over
impacted soil to reduce
infiltration and limit direct
contact.
Effective
Easily implemented.
Low 
Retained.
- Capping can be effective in reducing
infiltration; easily implemented.
Western Auto
Inspect and maintain existing
concrete paving and replace if
necessary.
Effective
Easily implemented.
Low 
Retained.
- Capping can be effective in reducing
infiltration; easily implemented.
Esso Tutu
Service Station
Inspect and maintain existing
asphalt paving and replace if
necessary.
Effective
Easily implemented.
Low 
Retained.
- Capping can be effective in reducing
infiltration; easily implemented.
—!
r~
O'Henry
Dry Cleaners
Install asphalt paving over
impacted soil to reduce
infiltration.
Effective
Easily implemented.
Low 
Retained.
- Capping can be effective in reducing
infiltration; easily implemented.
'--J
••0
G:\APROJECT\TUTU\PR00137\DATA\EVALCAPP.XLS
GERAGHTY & MIU.RR, INC
Table 4-8. 
Evaluation of In-Situ SVE and Bioventing Technologies Option on Property-Specific Basis, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Properties
Description
Effectiveness
Implementability 
Cost
Screening Comments
Curriculum Center 
In-situ SVE or bioventing in soil 
Potentially effective. Bioventing
and in-situ SVE in bedrock. 
would not be effective for
chlorinated VOCs.
Implementable. 
High costs for bedrock.
Costs would be prohibitively
high for soil due to small
volume.
Retained for bedrock.
Not retained for soil; not cost effective.
Ramsay Motors 
In-situ SVE or bioventing in soil. Potentially effective. SVE and
bioventing would be potentially
effective for BTEX concentrations.
Implementable. 
Moderate to high.
Not retained.
- Not cost effective due to building proximity.
Texaco Tutu 
In-situ SVE or bioventing in soil. 
Potentially effective. SVE and
Service Station 
bioventing would be potentially
effective for BTEX concentrations.
Implementable. 
Moderate to high.
Retained.
Tillett Gardens 
In-situ SVE or bioventing in soil. 
Not effective for manganese and PCBs. 
Not implementable. 
Not applicable.
Not retained.
- Not applicable for treatment of manganese
and PCBs.
Western Auto 
In-situ SVE or bioventing in soil. Not effective in tight clay formations. 
Implementable. 
Moderate to high.
Esso Tutu 
In-situ SVE or bioventing in soil. 
Potentially effective. SVE and
Service Station 
bioventing would be potentially
effective for BTEX. Bioventing would
not be effective due to the presence
of chlorinated VOCs.
Implementable. 
Moderate.
Not retained.
- Not effective in clay.
Retained.
O'Henry 
In-situ SVE or bioventing in soil 
Potentially effective. Bioventing would
Dry Cleaners 
and in-situ SVE in bedrock. 
not be effective due to the presence
of chlorinated VOCs.
Implementable. 
Moderate.
Retained.
SVE 
Soil vapor extraction.
PCBs 
Polychlorinated biphenyls.
BTEX 
Benzene, toluent, ethylbenzene, and xylene.
VOCs 
Volatile organic compounds.
G:\APROJECT\TUTU\PR00137\DATA\EVINSITU.XLS
GERAGHTY & MILLER, INC.
Table 4-9. 
Evaluation of Ex-Situ SVE and Biopiles Technologies Option on Property-Specific Basis, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Properties
Description
Effectiveness
Implementability
Cost
Screening Comments
Curriculum Center 
Excavate soil and treat using
ex-situ SVE or biopiles.
Ramsay Motors 
Excavate soil and treat using
ex-situ SVE or biopiles.
Texaco Tutu 
. 
Excavate soil and treat using
Service Station 
ex-situ SVE or biopiles.
This technology will not be effective
for unsaturated bedrock which may
contain chlorinated VOCs or DNAPL.
Potentially effective.
Not implementable for 
Due to small volume
bedrock. Implementable 
of soil, costs may be
for soil. 
high.
Potentially effective.
Difficult to implement
because UST is under
building.
Implementable.
Due to small volume
and location of soil,
costs would be
prohibitively high.
Moderate to high.
Retained for soil.
- Not retained for bedrock.
- Not effective or implementable for bedrock.
Not retained.
- Not cost effective.
- Difficult to implement.
Retained.
Tillett Gardens
Western Auto
Excavate soil and treat using
ex-situ SVE or biopiles.
Excavate soil and treat using
ex-situ SVE or biopiles.
Not effective treatment for 
Not applicable,
manganese or PCBs detected at
Tillett property.
May not be potentially effective due 
Implementable.
to the type of soil being treated
(clay).
Not applicable.
Costs would be
prohibitively high due
to presence of clay.
Not retained.
- Not applicable treatment for manganese
and PCBs.
Not retained.
- Not cost effective.
Esso Tutu
Service Station
O'Henry
Dry Cleaners
Excavate soil and treat using
ex-situ SVE or biopiles.
Excavate soil and treat using
ex-situ SVE or biopiles.
Potentially effective.
Potentially effective.
Implementable.
Implementable.
Moderate to high.
Moderate to high.
Retained.
Retained.
SVE 
Soil vapor extraction.
VOCs 
Volatile organic compounds.
DNAPL Dense non-aqueous phase liquids.
PCBs 
Polychlorinated biphenyls.
UST 
Underground storage tank.
TUT 
OO7
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GERAGHTY & MILLER, INC.
Table 4-10. Evaluation of Excavation and Off-Site Disposal Technology Option on Property-Specific Basis, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Properties
Description
Effectiveness
Implementability
Cost
Screening Comments
Curriculum Center
Ramsay Motors
Excavate soil, containerize, and
ship off-site for disposal.
Hazardous waste disposal may
be necessary.
Excavate soil, containerize, and
ship off-site for disposal.
Hazardous waste disposal may
be necessary.
Very effective at removing
impacted soil. Bedrock
would not be addressed.
Very effective at removing
impacted soil.
Implementable for soil. Not 
High
implementable for bedrock.
Implementable for soil. 
High
Difficult to implement
because impacted soils are
under building.
Retained for soil.
Not retained for bedrock.
- Not implementable.
Not retained.
- Difficult implementation and
high cost due to building
overlying UST.
Texaco Tutu
Service Station
Tillett Gardens
Western Auto
Esso Tutu
Service Station
O'Henry
Dry Cleaners
Excavate soil, containerize, and
ship off-site for disposal.
Hazardous waste disposal may
be necessary.
Excavate soil, containerize, and
ship off-site for disposal.
Hazardous waste disposal may
be necessary.
Excavate soil, containerize, and
ship off-site for disposal.
Hazardous waste disposal may
be necessary.
Excavate soil, containerize, and
ship off-site for disposal.
Hazardous waste disposal may
be necessary.
Excavate soil, containerize, and
ship off-site for disposal.
Hazardous waste disposal may
be necessary.
Very effective at removing
impacted soil.
Very effective at removing
impacted soil.
Implementable for soil.
High 
Retained.
Implementable for soil.
Very effective at removing 
Implementable for soil,
impacted soil.
Very effective at removing
impacted soil.
Very effective at removing
impacted soil. Bedrock
would not be addressed.
Implementable for soil.
Implementable for soil. Not
implementable for bedrock.
High 
Not retained.
- Not cost effective due to
small volume of soil.
High 
Retained.
High 
Retained.
High 
Retained.
C
o
UST 
Underground storage tank.
GERAGHTY & MILLER. INC.
O
Table 4-11. Summary of Proposed Pumping Rates for New Recovery Wells, Tutu Wells
Site, St. Thomas, U.S. Virgin Islands.
Groundwater Remedial Alternative
Proposed Containment Wells
RW-1
RW-2
RW-3
RW-4
RW-5
Total Containment Wells
Supply Wells with POETs
Esso Source Control
Texaco Source Control
GRA2
Source Containment
and POETs
(gpm)
-
-
—
20
35
55
15
10
30
110
GRA3
Plume
Containment
(gpm)
15
15
15
-
~
45
•
10
30
85
Pumoina Scenarips
GRA4
Source and
Plume Containment
(gpm)
15
15
15
20
35
100
—
10
30
140 **
Pumping scenarios should not exceed safe yield of catchment area of 118 gpm.
Estimated pumping rates are based on available site data. Final pumping rates will be
based on pilot studies and initial operations data.
* * 
Source control at the two service stations is assumed to be of short duration,
ranging from 3 to 7 years.
gpm 
Gallons per minute.
GRA 
Groundwater remedial alternative.
POET 
Point of entry treatment.
No pumpages.
G:\APROJECT\TUTU\PfW013.037\DATA\SUMPMP1 .XLS
GERAGHTY & MILLER, INC. 
TUT 007 
2183
Table 4-12. Summary of Potential POET Supply Well Installations for GRA 2, Tutu Wells Site, U.S. Virgin Islands.
POET Supply Well
GRA 2
Average
Flow Rate
(gpm)
GRA 2
Design
Flow Rate
(gpm)
Contaminants of
Concern
Design
Concentration
(ppb)
Maximum
Contaminant
Limit (ppb)
Proposed Treatment
Four Winds 1
10
10
1 ,2-Dichloroethene
64
GAC Unit
Steele
1.25
10
1,2-Dichloroethene
100
GAC Unit
La Place
1.25
10
1,2-Dichloroethene
95
GAC Unit
Matthias
1.25
10 
1,2-Dichloroethene
Trichloroethene
15
6
5
5
GAC Unit
Smith 
1.25
Total Average Flow (gpm) 
15
Total Average Flow (gpd) 
21,600
10 
1,2-Dichloroethene
Tetrachloroethene
Trichloroethene
39
19
110
5
5
5
GAC Unit
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POET 
Point of entry treatment.
GRA 
Groundwater remedial alternative.
gpm 
Gallons per minute.
ppb 
Parts per billion.
GAC 
Granular activated carbon.
gpd 
Gallons per day.
GERAGHTYff MILLER, INC
o
Table 4-13. 
Half-Lives of Chlorinated Compounds in Groundwater, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Chlorinated
Compounds
PCE
TCE
Vinyl chloride
1,2-DCE
Range of Half-Lives
in Groundwater
1 to 2 years
10.7 months to 4.5 years
2 months to 7.9 years
2 months to 7.9 years
Average Half-Lives
in Groundwater
1 .5 years
2.7 years
4.0 years
4.0 years
Half-lives taken from Howard and others (1991). These half-lives are estimated scientific
judgments based on published data for field or laboratory test results for aerobic degradation.
PCE 
Tetrachloroethene
TCE 
Trichloroethene
1,2-DCE 
1,2-Dichloroethene (includes both cis- and trans-isomers).
G:\APROJECT\TUTU\PR0013.037\DATA\HLFLIVES.XLS
"H 'T 
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GERAGHTY & MILLER, INC. 
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Table 4-14. 
Estimated Natural Degradation Rates for Groundwater Contaminants, Tutu Well Site, St. Thomas, U.S. Virgin Islands.
Chlorinated
Compound
Assumed
Initial
Concentration
(ug/L)
Concentration
After One
Half-Life
(ug/L)
Concentration
After Two
Half-Lives
(ug/L)
Concentration
After Three
Half-Lives
(ug/L)
USEPA MCL and
Estimated Time to
Achieve MCL Using
Maximum Half-Lives
PCE
1.2-DCE
TCE
Initial Total
(2.0 years max.)
58.8 
29.4 (1.5 years ave.)
(1.0 year min.)
(7.9 years max.)
29.4 
14.7 
(4.0 years ave.)
(0.167 year min.)
(4.5 years max.)
11.8 
5.9 (2.7 years ave.)
(0.89 
year min.)
100.0
(4.0 years max.)
14.7 
(3.0 years ave.)
(2.0 years min.)
(15.8 
years max.)
7.35 (8.0 years ave.)
(0.334 year min.)
(9.0 years max.)
2.95 
(5.4 years ave.)
(1.78 years min.)
(6.0 years max.)
7.35 
(4.5 years ave.)
(3.0 years min.)
(23.7 
years max
3.65 
(12.0 years ave.
(0.501 year min.
(13.5 years max
1.475 (8.1 years ave,
(2.67 years min.
(7.10 years max.)
5.0 (5.33 
years ave.)
(3.56 years min.)
(0 years max.)
70/100" (0 years ave.)
(0 years min.)
(5.58 years max.)
5.0 (3.34 
years ave.)
(1.10 years min.)
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Half-lives for groundwater contaminants are from Howard and others (1991).
Initial concentration was assumed to be 100 ug/L, which represents maximum concentration that may not be captured by
proposed recovery wells. The ratio of chlorinated compounds detected at the Matthias Supply Well were used to calculate a
total concentration of 100 ug/L. 
Concentration variations due to formation of breakdown products are not included.
MCL 
Maximum contaminant level.
PCE 
Tetrachloroethene.
1,2-DCE 
1,2-Dichloroethene.
TCE 
Trichloroethene.
MCLs for cis-1,2-DCE (70 ug/L) and trans-1,2-DCE (100 ug/L).
max. 
Maximum,
ave. 
Average,
min. 
Minimum.
ug/L 
Micrograms per liter.
G:\APROJECTYTUTU\PR0013.037\DATA\NATOEGRD .XLS
GERAGHTY & MILLER, INC.
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Table 4-15. 
Range of Values for Travel-Time and Natural Degradation of Tetrachloroethene, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Range of
Travel-Time
Calculation
Maximum
Average
Minimum
Groundwater
Hydraulic
Conductivity
(feet per day)
2.82
1.92
1.02
Effective
Porosity
0.14
0.2
0.4
Groundwater
Flow
Velocity
(feet per day)
1.39
0.661
0.176
Estimated Time to
Achieve MCL
for PCE
7. 10 years (2,592 days)
5.33 years (1,945 days)
3.56 years (1,299 days)
Length of
Downgradient
Migration
(feet)
3,603
1,286
229
Time to achieve MCL is based on half-lives for groundwater contaminants are from Howard and other (1991).
Initial concentration was assumed to be 100 micrograms per liter (ug/L) total VOCs, which represents
maximum concentration that may not be captured by proposed recovery wells. The ratio of chlorinated compounds
detected at the Matthias Supply Well were used to calculate a total concentration of 100 ug/L. Assumed initial
concentration of PCE is 58.8 ug/L.
PCE 
Tetrachloroethene.
MCL 
Maximum contaminant level.
VOCs 
Volatile organic compounds.
03
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GERAGHTY & MILLER, INC
o
Table 5-1. 
Evaluation of NCP Criteria for Soil Remedial Alternatives, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Overall 
Compliance 
• 
Reduction
Protection of 
with 
Long-Term 
of Toxicity,
Human Health 
Anticipated 
Effectiveness 
Mobility, 
Short-Term
Description 
and Environment 
ARARs 
and Permanence 
and Volume 
Effectiveness 
Implementability
SRA 1: 
Unfavorable 
Unfavorable 
Unfavorable
No Action/
Institutional Controls
SRA 2: 
Favorable 
Unfavorable 
Moderately
Institutional Controls/ 
Favorable
Capping
SRA 3: 
Favorable 
Favorable 
Favorable
Institutional Controls/
Capping/ln-Situ SVE/
Excavation and Off-Site Disposal
SRA 4: 
Favorable 
Favorable 
Favorable
Institutional Controls/
Capping/Ex-Situ SVE/
Excavation and Off-Site Disposal
SRA 5: 
Favorable 
Favorable 
Favorable
Institutional Controls/Capping/
Excavation and Off-Site Disposal
Unfavorable 
Favorable 
Favorable
Unfavorable 
Moderately 
Moderately
Favorable 
Favorable
Favorable 
Favorable 
Moderately
Favorable
Favorable 
Moderately 
Moderately
Favorable 
Favorable
Favorable 
Favorable 
Moderately
Favorable
U.S. Virgin Islands 
Community
Cost 
Acceptance * 
Acceptance *
Favorable
Moderately
Favorable
Moderately 
--
Favorable
Moderately
Favorable
Moderately
Favorable
NCP 
National Contingency Plan.
ARARs 
Applicable or relevant and appropiate requirements.
* 
Acceptance criteria will be assessed following comment on the Remedial Investigation and Feasibility Study (RI/FS) Reports and proposed plan.
SRA 
Soil remedial alternative.
Unfavorable 
Medium specific-term indicating the alternative does not address the goal adequately.
Moderately Favorable 
Medium specific-term indicating an acceptable level of comfort based on U.S. Environmental Protection Agency (USEPA) guidance. Other alternatives may
address the goal more effectively.
IT: 
Favorable 
Medium specific-term indicating an acceptable level of satisfaction of goals, based on USEPA guidance.
— I SVE 
Soil vapor extraction.
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GERAGHTY & MILLER, INC
Table 5-2.
Evaluation of NCR Criteria for Groundwater Remedial Alternatives, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Description
Overall
Protection of
Human Health
and Environment
Compliance
with
Anticipated
ARARs
Long-Term
Effectiveness
and Permanence
Reduction
of Toxicity,
Mobility,
and Volume
Short-Term
Effectiveness
Implementability
Cost
U.S. Virgin Islands
Acceptance *
Community
Acceptance "
GRA 1:
No Action/
Institutional Controls
Unfavorable 
Unfavorable 
Unfavorable 
Unfavorable 
Favorable 
Favorable 
Favorable
GRA 2: 
Unfavorable 
Favorable
Institutional Controls/
Source Containment/
POET Systems/Treatment Discharge
GRA 3: 
Favorable 
Favorable
Institutional Controls/
Plume Containment/
Treatment/Discharge
GRA 4: 
Favorable 
Favorable
Institutional Controls/
Source and Plume Containment/
Treatment/Discharge
Unfavorable 
Moderately 
Moderately 
Moderately 
Moderately
Favorable 
Favorable 
Favorable 
Favorable
Favorable
Favorable
Moderately
Favorable
Favorable
Moderately
Favorable
Moderately
Favorable
Moderately
Favorable
Moderately
Favorable
Moderately
Favorable
Moderately
Favorable
NCP
ARARs
*
GRA
Unfavorable
Moderately Favorable
Favorable
POET
National Contingency Plan.
Applicable or relevant and appropiate requirements.
Acceptance criteria will be assessed following comment on the remedial investigation and feasibility study (RI/FS) report and proposed plan.
Groundwater remedial alternative.
Medium specific-term indicating the alternative does not address the goal adequately.
Medium specific-term indicating an acceptable level of comfort based on U.S. Environmental Protection Agency (USEPA) guidance. Other alternatives
may address the goal more effectively.
Medium specific-term indicating an acceptable level of comfort based on USEPA guidance.
Point-of-entry treatment.
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GERAGHTY & MILLER. INC.
o
Table 5-3. Cost Estimate - SRA 1 (No Action/Institutional Controls), Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
ITEMS
QUANTITY
UNIT
UNIT COST
TOTAL COST
CAPITAL COSTS
Deed Restrictions
L.S.
$10,000
Subtotal
Administration & Legal Costs (20%)
Contingency (25%)__________
TOTAL CAPITAL COST - TREATMENT
$10,000
$10,000
$2,000
$2,500
$14,500
TOTAL CAPITAL COST - SRA 1
GRAND TOTAL - SRA 1
SAY 
$15,000
$15,000
SRA 
Soil remedial alternative.
L.S. 
Lump sum.
Source (design assumptions) of capital costs is presented in Appendix C.
g:\aprojeot\tutu\prO013.037\data\SR A1 CST.XLS
GERAGHTY & MILLER, INC.
TUT 
OO7 219O
Page 1 of 2
Table 5-4. Cost Estimate - SRA 2 (Institutional Controls/Capping), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
QUANTITY
UNIT
UNIT COST
TOTAL COST
CAPITAL COSTS
Deed Restrictions
Pavement Restoration & Capping
Curriculum Center
Ramsay Motors
Texaco Tutu Service Station
Tillett Gardens
Esso Tutu Service Station
Western Auto
O'Henry Dry Cleaners
L.S.
$10,000
27
4O
25
3
41
117
44
TOTAL CAPITAL COST - SRA 2
TOTAL CAPITAL COST - SCP AT ESSO (In-Situ SVE)
TOTAL CAPITAL COST - SCP AT TEXACO (In-Situ SVE)
TOTAL CAPITAL COST - SRA 2 AND SCPs
O&M (ANNUAL) COSTS - SRA 2
Pavement & Cap Maintenance
(Sealing, patching)
$10,000
S.Y.
C.Y.
S.Y.
S.Y.
S.Y.
S.Y.
S.Y.
Subtotal
$20
$400
$20
$20
$20
$20
$20
Administration & Legal Costs (20%)
Engineering Design (10%)
Construction Supervision (15%)
Contingency (25%)
TOTAL CAPITAL COST -
rE)
SVE)
SAY
$540
$16,000
$500
$60
$820
$2,340
$880
$31,140
$6,228
$3,114
$4,671
$7,785
$52,938
$53,000
$53,000
$150,000
$135,000
$338,000
Curriculum Center
Ramsay Motors
Texaco Tutu Service Station
Tillett Gardens
Esso Tutu Service Station
Western Auto
O'Henry Dry Cleaners
27
370
25
3
41
117
44
S.Y.
S.Y.
S.Y.
S.Y.
S.Y.
S.Y.
S.Y.
Subtotal
$3
$1
$3
$3
$3
$3
$3
Administration & Legal Costs (15%)
Contingency (25%)
TOTAL ANNUAL O&M COST
O&M (ANNUAL) PRESENT
Pavement & Cap Replacement
WORTH - SRA
1
2, YEAR 30 (3% discount
L.S.
rate)
$16,060
O&M PRESENT WORTH - SRA 2, YEAR 15 (3% discount rate)
TOTAL O&M PRESENT WORTH -
SRA 2
SAY
$81
$370
$75
$9
$123
$351
$132
$1,141
$171
$285
$1,597
$31,310
$16,060
$10,309
$41,619
$42,000
S:\APROJECTVrUTU\PR0013.03 7\DATA\SRA2CST.XLS
GERAGHTY & MILLER, INC.
TUT 
007 2191
Page 2 of 2
Table 5-4. Cost Estimate - SRA 2 (Institutional Controls/Capping), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
O&M (ANNUAL) COSTS
SCP at Esso
SCP at Texaco
QUANTITY
(TO YEAR 5) - SCPs
1
1
UNIT
L.S.
L.S.
UNIT COST
$20,000
$67,000
TOTAL COST
$20,000
$67,000
O&M (ANNUAL) PRESENT WORTH - SCPs, YEAR 5 (3% discount rate) 
$398,434
TOTAL O&M PRESENT WORTH - SCPs (In-Situ SVE) 
• 
SAY 
$399,000
TOTAL O&M PRESENT WORTH - SRA 2 AND SCPs 
$441,000
GRAND TOTAL - SRA 2 
$95,000
GRAND TOTAL - SRA 2 AND SCPs 
$779,000
L.S. 
Lump Sum.
C.Y. 
Cubic yard.
S.Y. 
Square yard.
SRA 
Soil remedial alternative.
SCP 
Source control plan.
O&M 
Operation and maintenance.
Source (design and O&M assumptions) used for cost estimates is presented in Appendix C.
G:\APROJECT\TUTmPfl0013.037\DATA\SRA2CST.XLS
GERAGHTYS? MILLER, INC. 
TUT O07 2192
Page 1 of 3
Table 5-5. Cost Estimate - SRA 3 (Institutional Controls/Capping/In-Situ SVE [Soil and Bedrockl/Excavation and Off-Site Disposal),
Tutu Walls Site, St. Thomas, U.S. Virgin Islands.
v ITEMS
CAPITAL COSTS
Deed Restrictions
Pavement Restoration & Capping
Ramsay Motors
Tillett Gardens
Curriculum Center
Excavation
Off-Site Disposal
Site Restoration
Excavated soil sample analysis
Western Auto
Excavation
Off-Site Disposal
Site Restoration
Excavated soil sample analysis
In-Situ SVE Systems
Curriculum Center (in bedrock)
O'Henry Dry Cleaners(in soils)
O'Henry Dry Cleaners(in bedrock)
*\
QUANTITY 
UNIT
1 
L.S.
40 
C.Y.
3 
S.Y.
5 
C.Y.
5 
C.Y.
5 
C.Y.
1 
EA.
181 
C.Y.
146 
C.Y.
181 
C.Y.
9 
EA.
1 
L.S.
1 
L.S.
1 
L.S.
Subtotal
Administration & Legal
UNIT COST
$10,000
$400
$20
$70
$2,230
$50
$1,500
$70
$2,230
$50
$1,500
$170,000
$50,000
$130,000
Costs (20%)
Engineering Design (10%)
Construction Supervision (15%)
TOTAL CAPITAL COST - SRA 3
TOTAL CAPITAL COST - SCP AT ESSO (In-Situ SVE)
TOTAL CAPITAL COST - SCP AT TEXACO (In-Situ SVE)
TOTAL CAPITAL COST - SRA 3 AND SCPs
O&M (ANNUAL) COSTS (TO YEAR 5) - SRA 3
Pavement & Cap Maintenance
(Sealing, patching)
Ramsay Motors
Tillett Gardens
In-Situ SVE Systems
Curriculum Center (in bedrock)
O'Henry Dry Cleaners(in soils)
O'Henry Dry Cleaners(in bedrock)
V
Contingency (25%)
TOTAL CAPITAL COST
370 
S.Y.
3 
S.Y.
1 
L.S.
1 
L.S.
1 
L.S.
Subtotal
Administration & Legal
Contingency (25%)
TOTAL ANNUAL O&M
_
SAY
$1
$3
$35,OOO
$14,500
$35,000
Costs (15%)
COST
TOTAL COST
$10,000
$16,000
$60
$350
$11,150
$250
$1,500
$12,670
$325,580
$9,050
$ 1 3,500
$170,000
$50,000
$130,000
$750,110
$150,022
$75,011
$112,517
$187,528
$1,275,187
$1,276,000
$1,276,000
$150,000
$135,000
$1,561,000
$370
$9
$35,000
$14,500
$35,000
$84,879
$12,732
$21 ,220
$118,831
(continued on next page)
G:\APfl OJECT\TUTU\PR0013;037\DATMSRA3CST.XLS
GERAGHTY & MILLER, INC.
TUT 
007 
2193
Page 2 of 3
Table 5-5. Cost Estimate - SRA 3 (Institutional Controls/Capping/In-Situ SVE [Soil and Bedrockl/Excavation and Off-Site Disposal),
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
QUANTITY
UNIT
UNIT COST
TOTAL COST
O&M (ANNUAL) COSTS (TO YEAR 5) - SRA 3 (continued)
O&M (ANNUAL) PRESENT WORTH - SRA 3, YEAR 1 to 5 (3% discount rate) 
$544,208
O&M (ANNUAL) COSTS (YEAR 6 TO 30) - SRA 3
Pavement & Cap Maintenance
(Sealing, patching)
Ramsay Motors
Tiliett Gardens
In-Situ SVE Systems
Curriculum Center (in bedrock)
O'Henry Dry Cleaners(in bedrock)
370 
S.Y. 
$1
3 
S.Y. 
$3
1 
L.S. 
$35,000
1 
L.S. 
$35,000
Subtotal
Administration & Legal Costs (15%)
Contingency (25%)
TOTAL ANNUAL O&M COST
O&M (ANNUAL) PRESENT WORTH - SRA 3, YEAR 6 to 30 (3% discount rate)
_ EQUIPMENT INSTALLATION. AND MATERIAL REPLACEMENT - SRA 3
/-•— v
lajor Equipment
Minor Equipment
Pavement & Cap Replacement
(Ramsay Motors & Tiliett only)
1 
L.S. 
$160,000
O&M PRESENT WORTH (Year 1 5)
(3% discount rate)
1 
L.S. 
$5,000
O&M PRESENT WORTH (Years 5, 10, 15, 20, 25)
(3% discount rate)
1 
L.S. 
$16,060
O&M PRESENT WORTH (Year 15)
(3% discount rate)
$370
$9
$35,000
$35,000
$70,379
$10,557
$17,595
$98,531
$1,479,983
$160,000
$102,704
$5,000
$16,400
$16,060
$10,309
TOTAL O&M PRESENT WORTH - SRA 3
O&M (ANNUAL) COSTS (TO YEAR 5) - SCPs
SCP at Esso
SCP at Texaco
L.S.
L.S.
$20,000
$67,000
$2,154,000
$20,000
$67,000
O&M (ANNUAL) PRESENT WORTH - SCPs, YEAR 5 (3% discount rate)
TOTAL O&M PRESENT WORTH - SCPs (In-Situ SVE)
/"""-""OTAL O&M PRESENT WORTH - SRA 3 AND SCPs
SAY
GRAND TOTAL - SRA 3
GRAND TOTAL - SRA 3 AND SCPs
G:\APnOJECT\ TOTU\PR0013.O37\OATA\SRA3CST.XLS
$398,434
$399,000
$2,553,000
$3,430,000
$4,114,000
GERAGHTY & MILLER, INC.
TUT 
007 2194
Page 3 of 3
Table 5-5. Cost Estimate - SRA 3 (Institutional Controls/Capping/In-Situ SVE (Soil and Bedrockl/Excavation and Off-Site Disposal),
Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
.«>*>4"S. 
Lump sum.
NA. 
Each.
,Y. 
Square yard.
C.Y. 
Cubic yard.
SVE 
Soil vapor extraction.
O&M 
Operation and maintenance.
SRA 
Soil remediation alternative.
SCP 
Source control plan.
Source (design and O&M assumptions) used for cost estimates is provided in Appendix C.
G:\APROJECT\TUTU\PR0013.O37\DAT AVSR A3CST .XLS
GERAGHTY & MILLER, INC.
TUT 
007 219!
Table 5-6. Cost Estimate - SRA 4 (Institutional Controls/Capping/Ex-Situ SVE/ln-Situ SVE/Excavation and 
Page 1 of 3
On-Site Disposal), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
CAPITAL COSTS
Deed Restrictions
Pavement Restoration & Capping
Ramsay Motors
Tillett Gardens
Western Auto
Excavation
Off-Site Disposal
Site Restoration
Excavated soil sample analysis
Ex-Situ SVE Systems
Curriculum Center
O'Henry Dry Cleaners
In-Situ SVE Systems
Curriculum Center (in bedrock)
O'Henry Dry Cleanerstin bedrock)
QUANTITY 
UNIT
1 
L.S.
40 
C.Y.
3 
S.Y.
181 
C.Y.
146 
C.Y.
181 
C.Y.
9 
EA.
1 
L.S.
1 
L.S.
1 
L.S.
1 
L.S.
Subtotal
Administration & Legal
UNIT COST
$10,000
$400
$20
$70
$2,230
$50
$1,500
$10,000
$35,000
$170,000
$130,000
Costs (20%)
Engineering Design (10%)
Construction Supervision (15%)
Contingency (25%)
TOTAL CAPITAL COST -
TOTAL CAPITAL COST - SRA 4
TOTAL CAPITAL COST - SCP AT ESSO (In-Situ SVE)
TOTAL CAPITAL COST - SCP AT TEXACO (In-Situ SVE)
TOTAL CAPITAL COST - SRA 4
O&M (ANNUAL) COSTS (YEARS
Pavement & Cap Maintenance
(Sealing, patching)
Ramsay Motors
Tillett Gardens
Ex-Situ SVE Systems
Curriculum Center
O'Henry Dry Cleaners
In-Situ SVE Systems
Curriculum Center (in bedrock)
O'Henry Dry Cleanerstin bedrock)
TOTAL (ANNUAL) O&M COSTS
AND SCPs
1 AND 2) - SRA 4
370 
S.Y.
3 
S.Y.
1 
L.S.
1 
L.S.
1 
L.S.
1 
L.S.
Subtotal
Administration & Legal
Contingency (25%)
(YEARS 1 AND 2) - SRA 4
$1
$3
$12,000
$12,000
$35,000
$35,000
Costs (15%)
TOTAL COST
$10,000
$16,000
$60
$12,670
$325,580
$9,050
$13,500
$10,000
$35,000
$170,000
$130,000
$731,860
$146,372
$73,186
$109,779
$182,965
$1,244,162
$1,245,000
$150,000
$135,000
$1,530,000
$370
$9
$12,000
$12,000
$35,000
$35,000
$94,379
$14,157
$23,595
$132,131
(continued on next page)
G:\APROJECT\TUTU\PR0013.037\DATA\SRA4CST.XLS
GERAGHTY & MILLER, INC.
TUT 
O07 2196
Table 5-6. Cost Estimate - SRA 4 (Institutional Controls/Capping/Ex-Situ SVE/ln-Situ SVE/Excavation and 
page 2 of 3
On-Site Disposal), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS 
QUANTITY 
UNIT 
UNIT COST 
TOTAL COST
O&M (ANNUAL) COSTS (YEARS 1 AND 2) - SRA 4 (continued)
O&M PRESENT WORTH (Years 1 and 2) 
$252,832
(3% discount rate)
O&M (ANNUAL) COSTS (YEARS 3 TO 30) - SRA 4
Pavement & Cap Maintenance
(Sealing, patching)
Ramsay Motors
Tillett Gardens
In-Situ SVE Systems
Curriculum Center (in bedrock)
O 'Henry Dry Cleaners(in bedrock)
TOTAL (ANNUAL) O&M COSTS (YEARS
370 
S.Y.
3 
S.Y.
1 
L.S.
1 
L.S.
Subtotal
Administration & Legal
Contingency (25%)
3 TO 30) - SRA 4
$1
S3
$35,000
$35,000
Costs (15%)
O&M PRESENT WORTH (Years 3 to 30)
$370
$9
$35,000
$35,000
$70,379
$10,557
$17,595
$98,531
$1,742,715
(3% discount rate)
EQUIPMENT INSTALLATION. AND MATERIAL REPLACEMENT - SRA 4
Major Equipment 
1 
L.S. 
$160,000 
$160,000
O&M PRESENT WORTH (Year 15) 
$102,704
(3% discount rate)
Minor Equipment 
1 
L.S. 
$5,000 
$5,000
O&M PRESENT WORTH (Years 5, 10, 15, 20, 25) 
$16,400
(3% discount rate)
Pavement & Cap Replacement 
1 
L.S. 
$16,060 
$16,060
O&M PRESENT WORTH (Years 15) 
$10,309
(3% discount rate)
TOTAL O&M PRESENT WORTH - SRA 4 
$2,125,000
N
O&M (ANNUAL) COSTS (TO YEAR 5) - SCPs 
JH
SCP at Esso 
1 
L.S. 
$20,000 
$20,000 
,„
SCP at Texaco 
1 
L.S. 
$67,000 
$67,000 
O
O&M (ANNUAL) PRESENT WORTH - SCPs, YEAR 5 (3% discount rate) 
$398,434
5
TOTAL O&M PRESENT WORTH - SCPs (In-Situ SVE) 
SAY 
$399,000 
H
TOTAL O&M PRESENT WORTH - SRA 4 AND SCPs 
$2,524,000
G:\APROJECT\TUTU\PR0013.037\DATA\SRA4CST.XLS
GERAGHTY & MILLER, INC.
Table 5-6. Cost Estimate - SRA 4 (Institutional Controls/Capping/Ex-Situ SVE/ln-Situ SVE/Excavation and 
page 3 of 3
On-Site Disposal), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
QUANTITY
UNIT
UNIT COST
TOTAL COST
GRAND TOTAL - SRA 4
GRAND TOTAL - SRA 4 AND SCPs
$3,370,000
$4,054,000
L.S. 
Lump sum.
EA. 
Each.
C.Y. 
Cubic yard.
S.Y. 
Square yard.
O&M 
Operations and maintenance.
SVE 
Soil vapor extraction.
SRA 
Soil Remedial alternative.
SCP 
Source control plan.
Source (design and O&M assumptions) used for cost estimates is presented in Appendix C.
G:\APROJECT\TUTU\PR0013.037\DATA\SRA4CST.XLS
GERAGHTY & MILLER, INC.
TUT 
OO7 2198
Page 1 of 3
Table 5-7. Cost Estimate - SRA 5 (Institutional Controls/Capping/In-Situ SVE [Bedrockl/Excavation and
Off-Site Disposal), Tutu Wells Site, St. Thomas, U.S.Virgin Islands.
ITEMS 
QUANTITY
CAPITAL COSTS
Deed Restrictions 
1
Excavation 
305
Off-Site Disposal 
270
Site Restoration 
305
Excavated soil sample analysis 
1 6
In-Situ SVE Systems
Curriculum Center (in bedrock) 
1
O'Henry Dry CleanersOn bedrock) 
1
PAVEMENT RESTORATION & CAPPING
Ramsay Motors 
40
Tillett Gardens 
3
TOTAL CAPITAL COST - SRA 5
TOTAL CAPITAL COST - SCP AT ESSO (In-Situ SVE)
TOTAL CAPITAL COST - SCP AT TEXACO (In-Situ SVE)
TOTAL CAPITAL COST - SRA 5 AND SCPs
O&M (ANNUAL) COSTS - SRA 5
In-Situ SVE Systems
Curriculum Center (in bedrock) 
1
O'Henry Dry Cleaners (in bedrock) 
1
UNIT 
UNIT COST
LS. 
$10,000
C.Y. 
$70
C.Y. 
$2,230
C.Y. 
$50
EA. 
$1,500
L.S. 
$170,000
L.S. 
$130,000
C.Y. 
$400
S.Y. 
$20
Subtotal
Administration & Legal Costs (30%)
Engineering Design (10%)
Construction Supervision (15%)
Contingency (25%)
TOTAL CAPITAL COST -
SAY
LS. 
$35.000
LS. 
$35.000
TOTAL COST
$10,000
$21,350
$602,100
$15,250
$24,000
$170,000
$130,000
$16,000
$60
$988,760
$296,628
$98,876
$148,314
$247,190
$1.779.768
$1,780,000
$150,000
$135,000
$2,065,000
$35,000
$35,000
(continued on next page)
G:\APROJECT\TUTU\PR0013.037\DATA\SRA6CST.XLS
GERAGHTY & MILLER, INC.
TUT 
007 
2199
Page 2 of 3
Table 5-7. Cost Estimate - SRA 5 (Institutional Controls/Capping/ln-Situ SVE [BedrockJ/Excavation and
Off-Site Disposal), Tutu Wells Site, St. Thomas, U.S.Virgin Islands.
ITEMS
QUANTITY
UNIT
UNIT COST 
TOTAL COST
O&M (ANNUAL) COSTS - SRA 5 (continued)
Pavement & Cap Maintenance
(Sealing, patching)
Ramsay Motors
Tillett Gardens
O&M PRESENT WORTH
EQUIPMENT INSTALLATION. AND MATERIAL
Major Equipment
Minor Equipment
Pavement & Cap Replacement
370 
S.Y. 
$1
3 
S.Y. 
$3
Subtotal
Administration & Legal Costs (1 5%)
Contingency (25%)
TOTAL ANNUAL O&M COST
- SRA 5, YEAR 30 (3% discount rate)
REPLACEMENT
1 
L.S. 
$160,000
O&M PRESENT WORTH (Year 1 5)
(3% discount rate)
1 
L.S. 
$5,000
O&M PRESENT WORTH (Years 5, 10, 15, 20, 25)
(3% discount rate)
1 
L.S. 
$16,060
O&M PRESENT WORTH (Year 1 5)
(3% discount rate)
$370
$9
$70,379
$10,557
$17,595
$98,531
$1,931,239
$160,000
$102,704
$5,000
$16,400
$16,060
$10,309
TOTAL O&M PRESENT WORTH - SRA 5
O&M (ANNUAL) COSTS (TO YEAR 51 - SCPs
SCP at Esso
SCP at Texaco
L.S.
L.S.
$20,000
$67,000
O&M (ANNUAL) PRESENT WORTH - SCPs, YEAR 5 (3% discount rate)
TOTAL O&M PRESENT WORTH - SCPs (In-Situ SVE)
SAY
$2,061,000
$20,000
$67,000
$398,434
$399,000
TOTAL O&M PRESENT WORTH - SRA 5 AND SCPs
$2,460,000
G:\APHOJECTVrUTU\PHOO13.037\DATA\SRA6CST.XLS
GERAGHTY & MILLER, INC.
TUT
• Page 3 of 3
Table 5-7. Cost Estimate - SRA 5 (Institutional Controls/Capping/ln-Situ SVE [Bedrockl/Excavation and
Off-Site Disposal), Tutu Wells Site, St. Thomas, U.S.Virgin Islands.
ITEMS 
QUANTITY 
UNIT 
UNIT COST 
TOTAL COST
GRAND TOTAL - SRA 5 
$3,841,000
GRAND TOTAL - SRA 5 AND SCPs 
$4,525,000
L.S. 
Lump sum.
EA. 
Each.
S.Y. 
Square yard.
C.Y. 
Cubic yard.
SVE 
Soil vapor extraction.
O&M 
Operation and maintenance.
SCP 
Source control plan.
SRA 
Soil remediation alternative.
Source (design and O&M assumptions) used for cost estimates is provides in Appendix C.
x**"""*'N,
6:\APROJECT\TUTU\PROO13.037\DATA\SRABCST.XLS
GERAGHTY & MILLER, INC. 
TUT 
°°7 
22C>1
Table 5-8. 
Cost Estimate - GRA 1 (No Action/Institutional Controls), Tutu Wells Site, St. Thomas,
U.S. Virgin Islands.
ITEMS 
QUANTITY 
UNIT 
UNIT COST
CAPITAL COSTS
Deed Restrictions 
1 
L.S. 
$10,000
Subtotal
Administration & Legal Costs (20%)
Contingency (25%)
TOTAL CAPITAL COST - TREATMENT
TOTAL COST
$10
$10
$2,
$2,
$14
,000
,000
000
500
,500
TOTAL CAPITAL COST - GRA 1 
SAY
O&M (ANNUAL) COSTS
Groundwater Monitoring 
2 
Sample rounds/year 
$32,000
Subtotal
Administration & Legal Costs (15%)
Contingency (25%)
TOTAL ANNUAL O&M COST
O&M PRESENT WORTH, YEAR 30 (3% discount rate)
TOTAL O&M PRESENT WORTH - GRA 1
$15
$64
,000
,000
$64,000
$9,600
$16,000
$89,600
$1,756,196
$1,757,000
GRAND TOTAL - GRA 1
$1,772,000
GRA 
Groundwater remedial alternative.
L.S. 
Lump sum.
O&M 
Operation and maintenance.
Source (design and O&M assumptions) for cost estimates is provided in Appendix C.
G:\APROJECT\TUTU\PR0013.037\DATA\GRA1CST.XLS
GERAGHTY & MILLER, INC.
TUT 
007 
22O2
Table 5-9. Cost Estimate - GRA 2 (Institutional Controls/Source Containment/POET Systems/Treatment/ 
Pa0e 1 ot 3
Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
CAPITAL COSTS
Deed Restrictions
Site Preparation/Mobilization
Well Decommissioning
Site Acquisition
Groundwater Extraction System
Recovery Well Installation
Submersible Pumps (installed)
4"-6" 
Double-Walled PVC Pipe
(installed, with leak detection)
Pre-Treatment (PO4)
Low Profile Air Stripper (installed)
Thermal Oxidizer (installed, if required)
Liquid Phase Carbon
Treatment System (installed, if required)
Process Pumps
Piping (installed)
Discharge Pumps
Piping (installed)
Treatment Building (installed)
Electric
Electric Panel and Plant Wiring
Conduit to Wells
POET Systems (includes new well pump)
GAC Unit (1-10 gpm)
General Contractor
QUANTITY
1
1
12
1
2
2
2,300
1
1
1
1
4
200
2
50
600
1
2,300
5
1
UNIT
L.S.
LS.
EA.
L.S.
EA.
EA.
LF.
L.S.
LS.
L.S.
L.S.
EA.
L.F.
EA.
L.F.
S.F.
L.S.
L.F.
EA.
L.S.
Subtotal
UNIT COST
$10,000
$40,000
$1,000
$25,000
$38,000
$6,000
$65
$15,000
$25,000
$185,000
$35,000
$5,000
$10
$10,000
$30
$60
$50,000
$2
$5,000
$80,000
Administration & Legal Costs (20%)
Engineering Design (10%)
Construction Supervision (15%)
Contingency (25%)
TOTAL CAPITAL COST - GRA 2
TOTAL CAPITAL COST - SCP AT ESSO
TOTAL CAPITAL COST - SCP AT TEXACO
TOTAL CAPITAL COST - TREATMENT
TOTAL COST
$10,000
$40,000
$12,000
$25,000
$76,000
$12,000
$149,500
$15,000
$25,000
$185,000
$35,000
$20,000
$2,000
$20,000
$1,500
$36,000
$50,000
$4,600
$25,000
$80,000
$823,600
$164,720
$82,360
$123,540
$205,900
$1,400,120
$1,401,000
$100,000
$865,000
TOTAL CAPITAL COST - GRA 2 AND SCPs
$2,366,000
G:\APROJECT\TUTU\PROO13.O37\DATA\GRA2CST.XLS
GERAGHTY & MILLER, INC.
TUT 
OO7
Table 5-9. Cost Estimate - GRA 2 (Institutional Controls/Source Containment/POET Systems/Treatment/ 
Page 2 of 3
Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
O&M (ANNUAL) COSTS - GRA 2
Groundwater Monitoring
Electricity (Avg)
Chemical Usage (PO4)
Supplemental Fuel (Propane)
Carbon Replacement
Carbon Replacement (POET)
System Operation
(one person - full time)
POET System Monitoring (Avg)
Treatment System Monitoring (Avg)
O&M PRESENT WORTH
EQUIPMENT REPLACEMENT - GRA 2
Major Equipment Replacement
Minor Equipment Replacement
TOTAL O&M PRESENT WORTH - GRA 2
QUANTITY 
UNIT 
UNIT COST
2 
Sample rounds/year 
$32,000
240,000 j 
Kilowatt-hour 
$0.10
1 
L.S. 
$10,000
1 
L.S. 
$25,000
2,000 
Pounds of carbon 
$6
1,000 
Pounds of carbon 
$6
1 
L.S. 
$35,000
60 
EA. 
$1,000
12 
EA. 
$1,000
Subtotal
Administration and Legal Costs (15%)
Contingency (25%)
TOTAL ANNUAL O&M COST
- GRA 2, YEAR 30 (3% discount rate)
1 
L.S. 
$260,000
O&M PRESENT WORTH (Year 15)
(3% discount rate)
1 
L.S. 
$25,000
O&M PRESENT WORTH (Years 5, 10, 15, 20, 25)
(3% discount rate)
TOTAL COST
$64,000
$24,000
$10,000
$25,000
$12,000
$6,000
$35,000
$60,000
$12,000
$248,000
$37,200
$62,000
$347,200
$6,806,000
$260,000
$166,894
$25,000
$81,998
$7,055,000
O&M (ANNUAL) COSTS (TO YEAR 5) - SCPs
SCP at Esso
SCP at Texaco
1 
L.S. 
$6O,000
1 
L.S. 
$101,000
TOTAL ANNUAL O&M COST
O&M PRESENT WORTH - SCPs, YEAR 5 (3% discount rate)
TOTAL O&M PRESENT WORTH - GRA 2 AND SCPs
GRAND TOTAL - GRA 2
GRAND TOTAL - GRA 2 AND SCPs
$60,000
$101,000
$161,000
$738,000
$7,793,000
$8,456,000
$10,159,000
G:\APROJECTVTUTU\PR0013.037\DATA\GRA2CST.XLS
GERAGHTY & MILLER, INC.
TUT
OO7 
2204
Table 5-9. 
Cost Estimate - GRA 2 (Institutional Controls/Source Containment/POET Systems/Treatment/ 
Page 3 of 3
Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
QUANTITY
UNIT
UNIT COST
TOTAL COST
L.F. 
Linear feet.
S.F. 
Square feet.
L.S. 
Lump Sum.
EA. 
Each.
gpm 
Gallons per minute.
POET 
Point-of-Entry Treatment.
GAC 
Granular Activated Carbon.
PO4 
Orthophosphates.
O&M 
Operation and maintenance.
PVC 
Polyvinyl chloride.
SCP 
Source control plan.
GRA 
Groundwater remedial alternative.
Source (design and O&M assumptions) for cost estimates is provided in Appendix C.
G:\APROJECT\TUTU\PRO013.O37\DATA\GRA2CST.XLS
GERAGHTY & MILLER, INC.
TUT 
OO7 
22O5
Page 1 of 3
Table 5-10. 
Cost Estimate - GRA 3 (Institutional Controls/Plume Containment/Treatment/
Discharge), Tutu Wells Site, St. Thomas, U.S. 
Virgin Islands.
ITEMS 
QUANTITY
CAPITAL COSTS
Deed Restrictions 
1
Site Preparation/Mobilization 
1
Well Decommissioning 
17
Site Acquisition 
1
Groundwater Extraction System
Recovery Well Installation 
3
Submersible Pumps (installed) 
3
4"-6" 
Double-Walled PVC Pipe 
3,300
(installed, with leak detection)
Pre-Treatment (PO4) 
1
Low Profile Air Stripper (installed) 
1
Thermal Oxidizer (if required, installed) 
1
Liquid Phase Carbon
Treatment System (if required, installed) 
1
Process Pumps 
4
Piping (installed) 
200
Discharge Pump 
2
Piping (installed) 
50
Treatment Building (installed) 
600
Electric
Electric Panel and Plant Wiring 
1
Conduit to Wells 
3,300
General Contractor 
1
UNIT
L.S.
L.S.
EA.
L.S.
EA.
EA.
L.F.
L.S.
L.S.
L.S.
L.S.
EA.
L.F.
EA.
L.F.
S.F.
L.S.
L.F.
L.S.
Subtotal
UNIT COST
$10,000
$40,000
$1,000
$25,000
$38,000
$6,000
$65
$15,000
$25,000
$185,000
$35,000
$5,000
$10
$10,000
$30
$60
$50,000
$2
$90,000
Administration & Legal Costs (20%)
Engineering Design (10%)
Construction Supervision (1
Contingency (25%)
5%)
TOTAL CAPITAL COST - TREATMENT
TOTAL CAPITAL COST - GRA 3
TOTAL CAPITAL COST - SCP AT ESSO
TOTAL CAPITAL COST - SCP AT TEXACO
TOTAL COST
$10,000
$40,000
$17,000
$25,000
$114,000
$18,000
$214,500
$15,000
$25,000
$185,000
$35,000
$20,000
$2,000
$20,000
$1,500
$36,000
$50,000
$6,600
$90,000
$924,600
$184,920
$92,460
$138,690
$231,150
$1,571,820
$1,572,000
$100,000
$865,000
TOTAL CAPITAL COST - GRA 3 AND SCPs
$2,537,000
Q:\APROJECT\TUTU\PR0013.037\DATA\GRA3CST.XLS
GERAGHTY & MILLER, INC.
TUT 
007 
2206
Table 5-10. Cost Estimate - GRA 3 (Institutional Controls/Plume Containment/Treatment/
Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
QUANTITY
UNIT
UNIT COST
Page 2 of 3
TOTAL COST
O&M (ANNUAL) COSTS - GRA 3
Groundwater Monitoring
Electricity (Avg)
Chemical Usage (PO4)
Supplemental Fuel (Propane)
Carbon Replacement
System Operation
(one person - full time)
Treatment System Monitoring (Avg)
2 
Sample rounds/year
270,000 
Kilowatt-hour
1 
L.S.
1 
L.S.
2,000 
Pounds of carbon
1 
L.S.
12
EA.
$32,000
$0.10
$10,000
$25,000
$6
$35,000
$1,000
EQUIPMENT REPLACEMENT - GRA 3
Major Equipment Replacement
Minor Equipment Replacement
TOTAL O&M PRESENT WORTH - GRA 3
O&M (ANNUAL) COSTS (TO YEAR 5) - SCPs
SCP at Esso 
1
SCP at Texaco 
1
L.S.
L.S.
$60,000
$101,000
TOTAL ANNUAL O&M COST
O&M PRESENT WORTH, YEAR 5 (3% discount rate)
TOTAL O&M PRESENT WORTH - GRA 3 AND SCPs
$64,000
$27,000
$10,000
$25,000
$12,000
$35,000
$12,000
Subtotal
Administration and Legal Costs (15%)
Contingency (25%)
TOTAL ANNUAL O&M COST
!TH, YEAR 30 (3% discount rate)
1 
L.S. 
$260,000
O&M PRESENT WORTH (Year 15)
(3% discount rate)
1 
L.S. 
$49,035
O&M PRESENT WORTH (Years 5, 10, 15, 20, 25)
(3% discount rate)
$185,000
$27,750
$46,250
$259,000
$5,077,000
$260,000
$166,894
$49,035
$160,830
$5,405,000
$60,000
$101,000
$161,000
$738,000
$6,143,000
GRAND TOTAL
GRA 3
$6,977,000
G:\APROJECT\TUTU\PR0013.037\DATA\GRA3CST.XLS
GERAGHTY & MILLER, INC.
TUT 
007 
2207
Page 3 of 3
Table 5-10. Cost Estimate - GRA 3 (Institutional Controls/Plume Containment/Treatment/
Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS 
QUANTITY 
UNIT 
UNIT COST 
TOTAL COST
GRAND TOTAL - GRA 3 AND SCPs ______________________________________________$8,680,000
L.F. 
Linear feet.
S.F. 
Square feet.
L.S. 
Lump Sum.
EA. 
Each.
PVC 
Polyvinyl chloride.
PO4 
Orthophosphates.
O&M 
Operation and maintenance.
SCP 
Source control plan.
GRA 
Groundwater remedial alternative.
Source (design and O&M assumptions) for cost estimates is provided in Appendix C.
G:\APROJECTVUmj\PR0013.037\DATA\GRA3CST.XLS
GERAGHTY & MILLER, INC. 
' U'' °°7 
22°8
Page 1 of 3
Table 5-11. 
Cost Estimate - GRA 4 (Institutional Controls/Source and Plume Containment/Treatment/
Discharge), Tutu Wells Site, St. Thomas, U.S. 
Virgin Islands.
ITEMS 
QUANTITY
CAPITAL COSTS
Deed Restrictions 
1
Site Preparation/Mobilization 
1
Well Decommissioning 
17
Site Aquisition 
1
Groundwater Extraction System
Recovery Well Installation 
5
Submersible Pumps (installed) 
5
4"-6" 
Double-Walled PVC Pipe 
5,200
(installed, with leak detection)
Pre-Treatment (PO4) 
1
Low Profile Air Stripper (installed) 
1
Thermal Oxidizer (if required, installed) 
1
Liquid Phase Carbon
Treatment System (if required, installed) 
1
Process Pumps 
4
Piping (installed) 
200
Discharge Pump 
2
Piping (installed) 
50
Treatment Building (installed) 
600
Electric
Electric Panel and Plant Wiring 
1
Conduit to Wells 
5,200
General Contractor 
1
UNIT
L.S.
L.S.
EA.
L.S.
EA.
EA.
L.F.
L.S.
L.S.
L.S.
L.S.
EA.
L.F.
EA.
L.F.
S.F.
L.S.
L.F.
L.S.
Subtotal
UNIT COST
$10,000
$40,000
$1,000
$25,000
$38,000
$6,000
$65
$25,000
$40,000
$250,000
$50,000
$5,000
$10
$10,000
$30
$60
$70,000
$2
$125,000
Administration & Legal Costs (20%)
TOTAL CAPITAL COST - GRA 4
TOTAL CAPITAL COST - SCP AT ESSO
TOTAL CAPITAL COST - SCP AT TEXACO
TOTAL CAPITAL COST - GRA 4 AND SCPs
G:\APROJECT\TUTU\PR0013.037\DATA\GRA4CST.XLS
Engineering Design (10%)
Construction Supervision
Contingency (25%)
TOTAL CAPITAL COST -
GERAGHTY & MILLER, INC.
(15%)
TREATMENT
TUT 
O07
TOTAL COST
$10,000
$40,000
$17,000
$25,000
$190,000
$30,000
$338,000
$25,000
$40,000
$250,000
$50,000
$20,000
$2,000
$20,000
$1,500
$36,000
$70,000
$10,400
$125,000
$1,299,900
$259,980
$129,990
$194,985
$324,975
$2,209,830
$2,210,000
$100,000
$865,000
$3,175,000
2209 
J\
Page 2 of 3
Table 5-11. Cost Estimate - GRA 4 (Institutional Controls/Source and Plume Containment/Treatment/
Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
O&M (ANNUAL) COSTS
Groundwater Monitoring
Electricity (Avg)
Supplemental Fuel (Propane)
Chemical Usage (PO4)
Carbon Replacement
System Operation
(one person - full time)
Treatment System Monitoring (Avg)
QUANTITY 
UNIT 
UNIT COST
2 
Sample rounds/year 
$32,000
470,000 
Kilowatt-hour 
$0.10
1 
L.S. 
$38,000
1 
L.S. 
$10,000
3,000 
Pounds of carbon 
$6
1 
L.S. 
$35,000
12 
EA. 
$1,000
Subtotal
Administration & Legal Costs (15%)
Contingency (25%)
TOTAL ANNUAL O&M COST
O&M PRESENT WORTH, YEAR 30 (3% discount rate)
EQUIPMENT REPLACEMENT - GRA 4
Major Equipment Replacement
Minor Equipment Replacement
TOTAL O&M PRESENT WORTH - GRA
O&M (ANNUAL) COSTS (TO YEAR 5) -
SCP at Esso
SCP at Texaco
1 
L.S. 
$365,000
O&M PRESENT WORTH (Year 15)
(3% discount rate)
1 
L.S. 
$63,490
O&M PRESENT WORTH (Years 5, 10, 15, 20, 25)
(3% discount rate)
4
SCPs
1 
L.S. 
$60,000
1 
L.S. 
$101,000
TOTAL ANNUAL O&M COST
O&M PRESENT WORTH - SCPs, YEAR 5 (3% discount rate)
TOTAL O&M PRESENT WORTH - GRA 4 AND SCPs
TOTAL COST
$64,000
$47,000
$38,000
$10,000
$18,000
$35,000
$12,000
$224,000
$33,600
$56,000
$313,600
$6,147,000
$365,000
$234,294
$63,490
$208,241
$6,590,000
$60,000
$101,000
$161,000
$738,000
$7,328,000
GRAND TOTAL - GRA 4
$8,800,000
G:\APROJECT\TUTU\PR0013.037\DATA\GRA4CST.XLS
GERAGHTY & MILLER, INC.
TUT 
OO7
221C
Page 3 of 3
Table 5-11. Cost Estimate - GRA 4 (Institutional Controls/Source and Plume Containment/Treatment/
Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS 
QUANTITY 
UNIT 
UNIT COST 
TOTAL COST
GRAND TOTAL - GRA 4 AND SCPs_______________________________________________$10,503,000
L.F. 
Linear feet.
S.F. 
Square feet.
L.S. 
Lump Sum.
EA. 
Each.
PVC 
Polyvinyl chloride.
GRA 
Groundwater remedial alternative.
PO4 
Orthophosphates.
O&M 
Operation and maintenance.
SCP 
Source control plan.
Source (design and O&M assumptions) for cost estimates is provided in Appendix C.
G:\APROJECT\TUTU\PH0013.037\DATA\GRA4CST.XLS
GERAGHTY & MILLER, INC. 
'Ul 
°°7 
221i
^ap^ 
Table 5-12. 
Cost Comparison of Remedial Alternatives, Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
Remedial Alternative
SRA 1
SRA 2 and SCPs
SRA 3 and SCPs
SRA 4 and SCPs
SRA 5 and SCPs
GRA 1
GRA 2 and SCPs
GRA 3 and SCPs
GRA 4 and SCPs
Capital Cost
$15,000
$338,000
$1,561,000
$1,530,000
$2,065,000
$15,000
$2,366,000
$2,537,000
$3,175,000
Present Worth
O& M
-
$441,000
$2,553,000
$2,524,000
$2,460,000
$1,757,000
$7,793,000
$6,143,000
$7,328,000
Total Cost
$15,000
$779,000
$4,114,000
$4,054,000
$4,525,000
$1,772,000
$10,159,000
$8,680,000
$10,503,000
SRA 
Soil remedial alternative.
SCPs 
Source control plans for the Texaco and Esso properties.
GRA 
Groundwater remedial alternative.
O&M 
Operations and maintenance.
G:\APROJECT\TUTU\PRO013.037\DATA\TB612CST.XLS
GERAGHTY^ MILLER, INC. 
'Ul 
°°7 
22i2
Table 5-13. 
Summary of Comparative Analysis of Preferred Remedial Alternatives for Soil and
Groundwater, Tutu Wells Site, St. Thomas, U.S. 
Virgin Islands.
NCP Criteria 
Preferred Remedial Alternatives
Soil 
Groundwater
Protection of human health 
SRA 3 and 
GRA 4
and the environment. 
SRA 4
Compliance with ARARs. 
SRA 3 and 
GRA 4
SRA 4
Short-term effectiveness. 
SRA 2 
GRA 2
Long-term effectiveness. 
SRA 3 and 
GRA 4
SRA 4
Reduction of toxicity, 
SRA 4 
GRA 4
mobility, or volume.
Implementability 
SRA 3 and 
GRA 3
SRA 4
Cost 
SRA 2 
GRA 3
NCP 
National contingency plan.
SRA 
Soil remedial alternative.
GRA 
Groundwater remedial alternative.
ARARs 
Applicable or relevant and appropriate requirements.
G:\APROJECTVTUTU\PROO13.037\d4t.\COMPPnE.XLS
TUT 
007
GERAGHTY & MILLER, INC.
H
C
K!
TUTU WELLS SITE >l*sXr$\ f ^
^Wi^O^^fc^
r \ LT'- ^tj:^. 
VTA* 
s£r /$ 
*f ^,-^r= 
* •w:
1M|;>-^-1^
j SS//^ ^-vse1-^^-
SOURCE: USGS-EASTERN ST. THOMAS, VIRGIN ISLANDS, 1954 (PHOTOREVISED - 1982)
GERAGHTY
& MILLER, INC.
Services
A Heidemif Company
SITE LOCATION
TUTU WELLS SITE
ST. THOMAS, U.S. VIRGIN ISLANDS
FIGURE
1-1
TUT 
OO7 2215
EPA REGION II
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FIGURE 4-10
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EPA REGION II
SCANNING TRACKING SHEET
DOC ID #65014
DOC TITLE/SUBJECT:
TUTU WELLS SUPERFUND SITE
FIGURE 4-11
SCHEMATIC OF GROUNDWATER TREATMENT
OPTION FOR DISCHARGE TO SURFACE
WATER (Page: TUT 007 2231)
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LOCATED IN THE ADMINISTRATIVE RECORD FILE
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EPA REGION II
SCANNING TRACKING SHEET
DOC ID #65014
DOC TITLE/SUBJECT:
TUTU WELLS SUPERFUND SITE
FIGURE 5-1
CONCEPTUAL LAYOUT OF PROPOSED
GROUNDWATER REMEDIES
(Page: TUT 007 2232)
THIS DOCUMENT IS OVERSIZED AND CAN BE
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IP
APPENDIX A
SUMMARY OF DESIGN
ASSUMPTIONS FOR
POTABLE WATER DISCHARGE
COST ESTIMATE
GERAGHTY & MILLER, INC.
"UT
APPENDIX A
SUMMARY OF DESIGN ASSUMPTIONS FOR
POTABLE WATER DISCHARGE
COST ESTIMATE
To evaluate the cost for selecting discharge option for potable use, the various design
assumptions for potable treatment and discharge for Groundwater Remedial Alternative 4 (GRA 4)
are presented below. A detailed cost estimate for potable discharge for GRA 4 is presented in
Table A-l. Estimated costs are based on means cost estimating data, vendor information, and
engineering experience. The accuracy of such cost estimates is in conformance with current
USEPA guidance (+50 percent to -30 percent). Comparison of the cost for potable discharge with
the discharge to surface water option for GRA 4 demonstrates that the potable use discharge
option is much more costly. Because the potable use discharge option is not cost-effective and it
may be difficult to implement, this discharge option was not used in the assembly of GRAs in this
FS Report.
DESIGN ASSUMPTIONS FOR GROUNDWATER EXTRACTION SYSTEMS
1. 
Design assumptions for deed restrictions, mobilization, well decommissioning, and
groundwater extraction systems are the same as for the discharge to surface water.
DESIGN ASSUMPTIONS FOR SITE ACQUISITION
1. 
Cost of property purchase for treatment area and for obtaining right-of-ways for
recovery wells. Property required is assumed to be two times greater for a potable
(approximately 1.5 acres) vs. non-potable (approximately 0.75 acre) application.
DESIGN ASSUMPTIONS FOR GROUNDWATER TREATMENT SYSTEM
1. 
Chemical treatment for potable use assumed to be ion exchange (for inorganic
solids removal). Cost assumes all components necessary to run ion exchange unit.
GERAGHTY & MILLER, INC. 
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A-2
Component sizing is based on estimated flow rates. Backwash from the ion
exchange is assumed to be discharged to the publicly-owned treatment works
(POTW) (+ 1,200 gallons/day).
2. 
Sand niters are assumed to be dual media type with 4 gallon per minute/square foot
(gpm/sf) application rate, based on estimated flow. 
A portion or all of the
backwash (if required) will be recovered to the head of the plant.
3. 
For GRA 2 and GRA 3, a 5,000-gallon sludge holding tank (thickener) for process
waste from ion exchange and potentially a portion of backwash effluent (if
required) is assumed. For GRA 4, an 8,000-gallon tank and appurtenances are
assumed.
4. 
For GRA 2 and GRA 3, the nitric acid feed for pH adjustment is estimated at a
maximum of 2 gallons per day (gpd), if needed, and includes all associated
appurtenances. For GRA 4, the nitric acid feed for pH adjustment is estimated at a
maximum of 3 gpd, if needed, and includes all associated appurtenances.
5. 
The low-profile air stripper is a tray aeration unit with blower, controls, and
appurtenances. The unit costs are based on vendor quotes, based on the estimated
groundwater quality for each GRA and the estimated flow rate. Based on the
preliminary VOC concentrations, one stripper is assumed to be sufficient to treat
the groundwater.
6. 
The thermal oxidizer, if required, is assumed to be a 1,000-standard cubic feet per
minute (scfrn) unit for GRA 2 and GRA 3, with fan, controls, and appurtenances.
For GRA 4, a 2,000-scfrn unit is assumed with all associated appurtenances.
Preliminary calculations indicate that air treatment associated with the groundwater
treatment system is not required for any of the GRAs considered. Final design
g:^project\lutu'>pr0013.037VeportsUppa.doc
GERAGHTY & MILLER, INC.
A-3
evaluations may vary; therefore, thermal oxidation for treatment of air discharge is
included.
7. 
Liquid phase granular activated carbon (GAC) treatment is provided as a back-up
"polishing unit," in case the air stripper malfunctions. For GRA 2 and GRA 3,
GAC units were assumed to be two 2,000-pound units in parallel, with a
permanent installation. For GRA 4, GAC units are assumed to be configured in the
same manner except 3,000-pound units in parallel would be used. By-pass piping
can be provided to minimize carbon use.
8. 
Process pumps are assumed to be centrifugal pumps rated as follows:
• 
GRA 2 (four) 2-horsepower (hp) pumps, piping and appurtenances.
• 
GRA 3 (four) 2-hp pumps, piping and appurtenances.
• 
GRA 4 (four) 5-hp pumps, piping and appurtenances.
Potable use includes a backup pump.
9. 
Discharge pumps are assumed to be vertical turbine pumps rated as follows:
• 
GRA 2 (two) 2-hp pumps, piping and appurtenances.
• 
GRA 3 (two) 2-hp pumps, piping and appurtenances.
• 
GRA 4 (two) 5-hp pumps, piping and appurtenances.
Potable use includes a backup pump.
10. 
A holding tank is assumed to be aboveground, welded steel construction with
concrete foundation, level measuring devices, and appurtenances. The tank is sized
to provide approximately 1 day storage based on the estimated flow rate capacity
of the facility.
g:\aproject\tutu'^r0013.03TTepot1«\appa.(k)C
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—
GERAGHTY & MILLER, INC. 
O
A-4
11. 
A distribution tank, assumed to be an elevated welded steel tank with concrete
foundation, level measuring devices, and appurtenances, sized to provide
approximately 2 days' storage based on the estimated flow rate capacity of the
facility.
12. 
The treatment building is sized to accommodate major equipment components of
the treatment facility. The cost includes labor and equipment, and butler type
building set on a poured concrete foundation.
13. 
Lump sum cost for electrical includes Motor Control Center (MCC), starters,
electric service and connections, controls and control panel, leak detection, and
remote dial out. Electrical conduit will go to each well for the submersible pumps
and use the same trench as the extraction piping (it is assumed that no emergency
back up power will be provided).
14. 
It is assumed that for GRA 3 and GRA 4, water will continue to be supplied as it is
now, by rainwater cisterns or by trucking water.
Operation & Maintenance (O&M) Assumptions for GRAs
1. 
Electrical costs are for the well pumps, blowers, and process and discharge pumps
associated with the treatment units. An allowance for building heating and lighting
is also included. The power usage is estimated to be equivalent to 62 hp, operating
24 hours a day plus 25 percent. Cost estimates been made utilizing an average
price of electricity per kilowatt hour of $ 0.10.
2. 
Chemical usage based influent groundwater quality and estimated influent flow
rate, and vendor quotation. Storage is not provided because the product is
delivered in storage containers.
g:\aproject\tutu\pr0013.03T«porU\appa.doc
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GERAGHTY & MILLER, INC.
A-5
3. 
Carbon replacement is assumed to be minimal due to the redundancy provided by
the air stripper. For GRA 4, it is assumed that one unit change-out every year
(3,000 Ibs) will be performed.
4. 
Supplemental fuel for Therm-Ox is assumed to be propane. For the 1,000-scfm
unit, 10,000 therms/year (equivalent to 100,000 BTUs per year) at Sl.OO/therm is
assumed, and 15,000 therms/year is assumed for the 2,000-scfrn unit.
5. 
System operation assumes one full-time person for the treatment facility and
effluent monitoring.
6. 
System monitoring is expressed as a sampling average annually. It is assumed that
30 samples will be collected to monitor quality for potable use (1 sample every 2
weeks plus 4 will be required for compliance monitoring). Additional samples will
be collected and tested by the operator using a portable gas chromatograph (GC)
on average of two samples per week.
ASSUMPTIONS FOR EQUIPMENT INSTALLATION AND MATERIAL
REPLACEMENT
1. 
Major equipment replacement entails complete replacement of process equipment
such as air strippers, portable GC, GAC, and ion exchange units, and 10 percent of
the storage tanks' capital cost (for painting and maintenance)
2. 
Minor equipment replacement entails replacing pumps and blowers, etc., every 5
years (10 percent of chemical treatment and electrical costs, 5 percent of
groundwater recovery systems [includes well pumps and treatment building], SO
percent for discharge and process pumps and piping).
g:\aproject\tutu\pi0013.037Veports\appa.doc
"n n~ or)"7 •".><-.»"•.;• •••-•
GERAGHTY & MILLER, INC.
Table A-1. 
Estimated Cost of Potable Discharge Option for GRA 4 (Institutional Controls, Source and Plume Containment, page 1 of 2
Treatment, and Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS
CAPITAL COSTS
Deed Restrictions
Site Preparation/Mobilization
Well Decommissioning
Site Acquisition
Groundwater Extraction System
Recovery Well Installation
Submersible Pumps (Installed)
4"-6" Double-Walled PVC Pipe
(Installed, with Leak Detection)
Chemical Treatment (Ion Exchange)
Low Profile Air Stripper (Installed)
Thermal Oxidizer (If required, installed)
Sand Filters with Backwash Pump
Liquid Phase Carbon
Treatment System (If required. Installed)
Sludge Handling Equipment
Process Pumps
Piping (Installed)
Discharge Pump
Piping (Installed)
pH Adjustment System
Holding Tank
(144,000 gallons, installed)
Elevated Distribution Tank
(290,000 gallons, installed)
Treatment Building (Installed)
Portable GC Analyzer
Electric
Electric Panel and Plant Wiring
Conduit to Wells
General Contracting
QUANTITY
1
1
17
1
5
5
5,200
1
1
1
1
1
1
4
400
2
100
1
1
1
1,600
1
1
5,200
1
UNIT
L.S.
L.S.
EA.
L.S.
EA.
EA.
L.F.
L.S.
L.S.
L.S.
L.S.
L.S.
L.S.
EA.
L.F.
EA.
L.F.
LS.
LS.
L.S.
S.F.
LS.
L.S.
L.F.
LS.
Subtotal
UNIT COST
$10,000
$25,000
$1,000
$25,000
$38,000
$6,000
$65
$85,000
$40,000
$250,000
$70,000
$50,000
$20,000
$5,000
$10
$10,000
$30
$10,000
$180,000
$725,000
$60
$20,000
$100,000
$2
$240,000
Administration & Legal Costs (20%)
TOTAL CAPITAL COST - GRA 4
Engineering Design (10%)
Construction Supervision
Contingency (25%)
TOTAL CAPITAL COST -
(15%)
TREATMENT
TOTAL COST
$10,000
$25,000
$17,000
$25,000
$190,000
$30,000
$338,000
$85,000
$40,000
$250,000
$70,000
$50,000
$20,000
$20,000
$4,000
$20,000
$3,000
$10,000
$180,000
$725,000
$96,000
$20,000
$100,000
$10,400
$240,000
$2,578,400
$515,680
$257,840
$386,760
$644,600
$4,383,280
$4,384,000
G:\APROJECT\TUTU\PR0013.037\DATA\GRA4ACST.XLS
GERAGHTY & MILLER, INC.
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224O
Table A-1. 
Estimated Cost of Potable Discharge Option for GRA 4 (Institutional Controls, Source and Plume Containment, page 2 of 2
Treatment, and Discharge), Tutu Wells Site, St. Thomas, U.S. Virgin Islands.
ITEMS 
QUANTITY 
UNIT 
UNIT COST
O&M (ANNUAL) COSTS
Groundwater Monitoring 
2 
Sample rounds/year 
$32,000
Electricity (Avg) 
511,000 
Kilowatt-hour 
$0.10
Supplemental Fuel (Propane) 
1 
L.S. 
$15,000
Carbon Replacement 
3,000 
Pounds of Carbon 
$6
Chemical Usage 
1 
L.S. 
$10,000
Sludge Disposal (non-hazardous) 
350 
C.Y. 
$350
System Operation 
1 
L.S. 
$35,000
(One person - full time)
Treatment System Monitoring (Avg) 
30 
EA. 
$1,000
GC Chemical Buffer Solutions
and Equipment 
1 
L.S. 
$5,000
Subtotal
Administration & Legal Costs (10%)
Contingency (25%)
TOTAL ANNUAL O&M COST
O&M PRESENT WORTH, YEAR 30 (3% discount rate)
EQUIPMENT REPLACEMENT
Major Equipment Replacement 
1 
L.S. 
$365,500
O&M PRESENT WORTH (Year 1 5)
(3% discount rate)
Minor Equipment Replacement 
1 
L.S. 
$87,740
O&M PRESENT WORTH (Years 5, 10, 15, 20, 25)
(3% discount rate)
TOTAL O&M PRESENT WORTH - GRA 4
GRAND TOTAL - GRA 4
L.F. 
Linear feet.
S.F. 
Square feet.
L.S. 
Lump Sum.
EA. 
Each.
gpm 
Gallons per minute.
GAC 
Granular Activated Carbon.
PO4 
Orthophosphates.
O&M 
Operation and maintenance.
GC 
Gas-Chromatography.
Note: 
Refer to Appendix C for source (design and O&M assumptions) for cost estimates.
TOTAL COST
$64,000
$51,100
$15,000
$18,000
$10,000
$122,500
$35,000,
£
$30,000
$5,000
$350,600
$35,060
$87,650
$473,310
$9,277,065
$365,500
$234,600
"V-
$87,740
$287,774
$9,800,000
$14,184,000
' «?
G:\APROJECT\TUTU\PR0013.037\DATA\GRA4ACST.XLS 
GERAGHTI~& MILLER, INC.
TUT 
OO7
241
EPA REGION II
SCANNING TRACKING SHEET
DOC ID #65014
DOC TITLE/SUBJECT:
TUTU WELLS SUPERFUND SITE
FIGURE A-1
SCHEMATIC OF GROUNDWATER TREATMENT
OPTION FOR POTABLE USE
(Page: TUT 007 2242)
THIS DOCUMENT IS OVERSIZED AND CAN BE
LOCATED IN THE ADMINISTRATIVE RECORD FILE
AT THE
SUPERFUND RECORDS CENTER
290 BROADWAY, 18™ FLOOR
NEW YORK, NY 10007
II
APPENDIX B
SUMMARY OF CAPTURE ZONE ANALYSES
GERAGHTY & MILLER, INC. 
IUl 
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k::'"44
APPENDIX B
SUMMARY OF CAPTURE ZONE ANALYSES
CAPTURE ZONE ANALYSIS FOR
THE TEXACO TUTU SERVICE STATION
SOURCE CONTROL PLAN
For the purposes of this FS Report the following assumptions for the proposed Source
Control Plan for the Texaco Tutu Service Station were used to calculate the potential capture
zone for the proposed extraction wells. 
These assumptions are based on the aquifer
characteristics presented in the RI report (Geraghty & Miller, Inc. 1995) and the proposed Source
Plan prepared by Erler and Kalinowsky, Inc. (EKI) (1995a).
The proposed extraction wells for source control near the Texaco Tutu Service Station
include the following:
• Proposed Texaco Extraction Well TEW-1 will replace Monitoring Well TT-1 (at the
Texaco Tutu Service Station);
• Proposed Texaco Extraction Well TEW-2 will be located approximately 25 feet west
of Monitoring Well MW-7 (at the Vitelco Property).
In addition, a third shallow Texaco Extraction Well TEW-3 is proposed at the Texaco
Tutu Service Station as a contingency if proposed Texaco Extraction Well TEW-1 cannot obtain
the desired capture. Deep extraction wells TEW-ID, TEW-2D, and TEW-3D are also proposed
for groundwater monitoring and possibly pumping, if necessary, to achieve capture throughout
the vertical extent of groundwater contamination.
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GERAGHTY & MILLER, INC.
B-2
The well screens for the proposed extraction wells TEW-1 and TEW-2 would be placed at
170 feet to 140 feet msl (EKI 1995a). For groundwater modeling, EKI selected the elevation of
90 feet msl as the base of the aquifer (i.e., approximate saturated thickness of 72 feet) based on
the projected maximum depth of benzene, toluene, ethylbenzene, and xylene (BTEX)
contamination. This depth would be the designed maximum depth for capture of contaminants.
EKI (1995b) prepared a capture zone analysis based on numerical modeling of groundwater flow.
The predicted capture zone for the combined effect of pumpage from the two proposed primary
shallow Texaco Extraction Wells TEW-1 (at 20 gpm) and TEW-2 (at 10 gpm) was prepared by
EKI (1995b) and is shown on Figure 4-8.
CAPTURE ZONE ANALYSIS FOR
THE ESSO TUTU SERVICE STATION
SOURCE CONTROL PLAN
For the purposes of this FS Report, the following assumptions for the proposed Source
Control Plan for the Esso Service Station were used to calculate the potential capture zone for the
proposed extraction wells. These assumptions are based on the aquifer characteristics presented
in the RI report (Geraghty & Miller, Inc. 1995), the well selection and estimated pumping rates
from Forensic Environmental Services, Inc. (FES) (1995), and the proposed Source Control Plan
prepared by FES.
The proposed extraction wells for source control at the Esso Tutu Service Station include
the following: Monitoring Well SW-1, Monitoring Well SW-7, Monitoring Well CHT-3, and
Monitoring Well MW-9. Existing monitoring wells are proposed to be used as extraction wells
for the Esso Tutu Service Station.
FES prepared and plotted the results of capture zone analyses for the four proposed
extraction wells based on an aquifer thickness of 50 feet. This depth would be the designed
maximum depth for the capture of BTEX contaminants. For the purpose of this FS Report, the
predicted capture zones of the four proposed primary shallow extraction wells are shown on
Figure 4-8.
2246
GERAGHTY & MILLER, INC.
B-3
SITE-WIDE CAPTURE ZONE ANALYSIS
The dimensions of the capture zones for potential Recovery Wells RW-1, RW-2, RW-3,
RW-4, and RW-5 under the pumping scenario for GRA 4 were calculated using Equation 1
described below. The capture zones and locations of the recovery wells are shown on Figure 4-9.
Equation 1:
y = (Q/(2 71 TI) arctan (y/x) 
(USEPA 1991 c)
where
y = 
Distance from the center axis of the capture zone to the edge, in feet.
x = 
Distance from the recovery well along the axis of the capture zone to the
downgradient edge, in feet.
Q = 
Pumping rate of recovery well, in gallons per day (gpd).
T = 
Transmissivity of the formation, in gpd/foot.
I = 
Local hydraulic gradient. (I = change in hydraulic head/change in distance.)
To adequately plot the capture zones, three dimensions are needed:
W0 
The width of the capture zone in the immediate vicinity of the recovery well.
Xo 
The distance from the well to the downgradient extent of the capture zone.
W 
The maximum width of the capture zone, upgradient of the recovery well.
Solving Equation 1 for the above parameters, the following equations were obtained:
Equation 2: 
W0 - 
Q/(2 TI), and 
(USEPA 1987, 1991c)
Equations: 
Xo= 
Q/(27CTI) 
(USEPA 1987, 1991 c)
GERAGHTY & MILLER, INC. 
fUF 
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B-4
Using Equation 2, the pumping rate of the recovery well was calculated with the following
equation:
Q = 
W0 (2TI)
where
W0 
is measured on Figure 4-9.
T 
is obtained from the results of nearby pumping tests;
I 
is calculated from the groundwater contours shown on Figure 4-9.
The variables used to solve for the dimensions of capture zones are listed in Table B-l.
Equation 3 was used to calculate the distance X,.
where
Q 
is the pumping rate obtained from Equation 2, and T and I were the variables
described above.
Due to the high calculated pumping rate necessary for capture, two adjacent recovery
wells, Recovery Wells RW-2 and RW-3, were proposed for the capture of the southern plume of
chlorinated volatile organic compounds (VOCs).
;ffc- •
The optimum spacing of the pumping wells was calculated with the following equation:
Equation 4:
D = 
Q/(2 71TI)
using the variables in Table B-l,
Q = 
6.68 ft3/ min
T= 
0.14 ft2/ min
I = 
0.079
D = 
96.6 feet.
g:\aproject\tutu\PR0013.037\reports\captzone.doc
GERAGHTYcS? MILLER, INC. 
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Table B-1. Values Used to Determine Capture Zones and Pumping Rates of Proposed Pumping Wells, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Capture Zone 
Estimated 
Hydraulic 
Pumping 
Pumping 
Downgradient
Recovery 
Width (W0) 
Transmissivity (T) 
Gradient (1) 
Rate (Q) 
Rate (Q) 
Dimension (XJ
Well 
Location 
(feet) 
(ft2/min) 
(ft3/min) 
(gpm) 
(feet)
Esso Tutu Service
Station - Source Control Plan
MW-9 
26.9 
0.024 
0.0426 
0.33 2.5
SW-7 
26.9 
0.024 
0.0426 
0.33 2.5
SW-1 
26.9 
0.024 
0.0426 
0.33 2.5
CHT-3 
, 
26.9 
0.024 
0.0426 
0.33 2.5
•«' 
*™".)| 
•»«*-.
Site-Wide Recbverv Wells
RW-1 
Toe of northern plume 
170 
0.14 0.04 
1.9 
14.3
RW-2 
and
RW-3 
Toe of southern plume 
260 
0.14 (assumed) 
0.079 (assumed) 
5.75 43
RW-4 
LAGA/Curriculum Center 
250 
0.14 
0.033 
2.31 
17.5
RW-5 
O'Henry Dry Cleaners 
211 
0.14 0.079 
5.2 
35
Capture zone analyses for Texaco Extraction Wells TEW-1 and TEW-2 prepared by Erler & Kalinowski, Inc. (EKI, 1995b).
ftz/min 
Square feet per minute.
ft3/min 
Cubic feet per minute,
gpm 
Gallons per minute.
8.6
8.6
8.6
8.6
54.1
82.8
79.6
75.4
'--I
•-G
GERAGHTY & MILLER. INC
APPENDIX C
SUMMARY OF DESIGN
ASSUMPTIONS FOR
SOIL AND GROUNDWATER REMEDIATION
COST ESTIMATES
GERAGHTY & MILLER, INC. 
fUT °07 
2251 O
APPENDIX C
SUMMARY OF DESIGN ASSUMPTIONS FOR
SOIL AND GROUNDWATER REMEDIATION
COST ESTIMATES
Note: Estimated costs are based on Means Cost Estimating Data, vendor information, and
engineering experience. The accuracy of such cost estimates is in conformance with
current U.S. Environmental Protection Agency (USEPA) Guidance (+50 
percent to -30
percent).
SOIL
COST ASSUMPTIONS FOR DEED RESTRICTIONS
1. 
Deed Restrictions for soils are as described in SRA 1, and include estimated costs
for filing and application fees. Administrative and legal fees are included in a
separate line item.
DESIGN ASSUMPTIONS FOR CAPPING (ALL 
SITES)
1. 
6-inch thick, compacted gravel base.
2. 
For areas where there is pavement currently in place, installation will match
existing conditions.
3. 
3-inch thick layer of bituminous paving with seal coat.
4. 
At Ramsay Motors, it is assumed that complete replacement of concrete floor will
be required (4-inch thick slab on grade, 6-inch by 6-inch welded wire mesh
reinforcement, formed and in place). The cap will be formed concrete which is
GERAGHTY & MILLER, INC.
C-2
typically estimated by the cubic yard (CY). This is different that the estimated
costs for pavement capping which is estimated based on the area to be capped in
square yards (SY).
5. 
Estimated costs for pavement installation assumes that paving is completed at the
same time; under one paving contract.
6. 
Operation and maintenance (O&M) consists of inspection for cap integrity and, if
necessary, application of surface treatments to improve the effectiveness of asphalt
caps.
7. 
Complete replacement of each cap is assumed at year 15.
DESIGN ASSUMPTIONS FOR EXCAVATION AND OFF-SITE DISPOSAL (SRA 5)
1. 
Administrative, legal and engineering cost percentages are higher for this SRA
(when compared to other SRAs) due to the increased regulatory requirements and
administrative duties associated with the transport of 
hazardous material.
Engineering design includes work plan preparation, implementation plan and
permitting. Administrative and legal fees include tracking of manifests, filing,
contracting with haulers and disposal facilities, and an allowance for legal fees
related to the remedial action.
2. 
Excavation areas and volumes based on Table 4-5.
3. 
Cost to excavate includes labor and equipment, and excavation support (e.g., sheet
piling) where needed.
4. 
Cost of disposal assumes off-island disposal to southeast, United States. Includes
transport, freight, and disposal.
g:\aproject\tutu\prOO 1 3 .037Veports\FeasAppC.doc
GERAGHTY & MILLER, INC.
C-3
5. 
Site restoration includes importing clean backfill from a local source, compaction,
and restoration to or near current conditions.
6. 
It is assumed that one land disposal restriction (LDR) testing sample will be
required for every 20 cubic yards (CY) of soil excavated.
7. 
It is assumed that no O&M will be required after completion of the excavation and
disposal SRA.
DESIGN ASSUMPTIONS FOR m-SITU SOIL VAPOR EXTRACTION (SVE)
General Assumptions (for all properties)
1. 
Administrative and legal fees include filing, contracting with consultants and
vendors, and an allowance for legal fees related to the remedial action. Engineering
design fees include pilot testing, work plan preparation, design of SVE system and
preparation of an implementation plan and permitting. Construction fees include
environmental monitoring and construction observation.
2. 
Separate line items are provided for soil source control plans (SCPs) at Texaco
Tutu Service Station and Esso Tutu Service Station. These estimates are lump
sum amounts which represent the total estimated costs of the SCPs (including
engineering design, administrative and legal costs). These estimates are based on
independent consultant estimates taken from SCP designs currently being
formulated and are included for informational purposes.
3. 
SCPs are assumed to be in operation for 5 years.
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Curriculum Center (in Bedrock) (Assumes 30-Year Operation Life)
1. 
Site characterization of potential DNAPL locations.
2. 
Three-SVE wells to ± 60 feet below land surface (bis) (into bedrock). (20 standard
cubic feet per minute [scfrn] shall be evacuated from each well [total 60 scfin]).
3. 
One-5 horsepower (hp) blower with filter and moisture knockout and temporary
enclosure (skid mounted).
4. 
500 linear feet of trenching (2-feet wide x 4-feet deep).
5. 
500 linear feet of 4-inch diameter PVC pipe.
6. 
Trenching includes excavation, backfill, and compaction, and bedrock removal
(assumes 50 percent rock removal and restoration).
7.
Thermal oxidizer (Therm-Ox) for vapor phase treatment (100 scfrn unit). Where
ex-situ SVE is applied, Therm-Ox proposed will have sufficient capacity to treat
both air flow rates (100 scfrn-60scfrn = 40scfrn). 
No vapor treatment of
hydrochloric acid is assumed.
8. 
Cost for air permit and modeling, if necessary.
9. 
O&M costs:
• 
Electrical for blower and Therm-Ox $4,500/year (45,000 kW-hr/yr @
$0.10/kW-hr).
• 
System operator $12,000/year.
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• 
Air sampling (assumes 26 samples/year @ $500/sample).
• 
Supplemental fuel (propane) (5,000 therms/year @ $ 1.0/therm).
O'Henry Dry Cleaners (in Bedrock) (Assumes 30-Year Operation Life)
1. 
Site characterization of potential DNAPL locations.
2. 
Three-SVE wells to ± 40 feet below land surface (bis) (into bedrock).
3. 
One-5 horsepower (hp) blower with filter and moisture knockout and temporary
enclosure (skid mounted).
4. 
200 linear feet of trenching (2-feet wide x 4-feet deep).
5. 
200 linear feet of 4-inch diameter PVC pipe.
6. 
Trenching includes excavation, backfill, and compaction.
7. 
Therm-Ox for vapor phase treatment (100 scfm unit) where in-situ and ex-situ
SVE is applied it is assumed that the unit proposed will have adequate capacity
(100 scfin - 20 scfm = 80 scfm). A new unit is proposed when combined with
excavation and disposal
8. 
Cost for air permit and modeling, if necessary.
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9. 
O&M costs:
• 
Electrical for blower and Therm-Ox $4,500/year (45,000 kW-hr/yr @
$0.10/kW-hr).
• 
System operator $12,000/year.
• 
Air sampling (assumes 26 samples/year @ $500/sample).
• 
Supplemental fuel (propane) (5,000 therms/year @ $ 1.0/therm).
O'Henry Dry Cleaners (in Soils) (Assumes 5-Year Operation Life)
1. 
One-SVE well ± 20 feet bis.
2. 
One-2-hp blower with filter and moisture knockout on skid, and temporary
enclosure (skid mounted).
3. 
Blower skid placed adjacent to SVE well (minimal piping and trenching).
4. 
Vapor phase treatment is assumed to utilize the Therm-Ox unit proposed for in-situ
treatment of bedrock.
5. 
Cost for air permit, if needed.
6. 
O&M costs:
• 
Added electrical cost for the additional blower $ 2,500/year (25,000 kw-hr/yr
@ $ 0.10/kw-hr). Other costs for O & M are included for the in-situ SVE
system that is installed for bedrock.
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• 
Soil compliance sampling (assumes 4 samples/year TCL VOCs and sampling
equipment ($3,000/sample).
Texaco Tutu Service Station (In Soils) (Assumes 5-Year Operation Life)
1. 
Based on SCP and estimated costs prepared by Erler and Kalinowski, Inc.
Esso Tutu Service Station (In Soils) (Assumes 5-Year Operation Life)
1. 
Based on SCP and estimated costs prepared by Forensic Environmental, Inc.
DESIGN ASSUMPTIONS FOR EX-SITU SVE
(By Property)
General Assumptions (for all properties)
1. 
Administrative and legal fees include filing, contracting with consultants and
vendors, and an allowance for legal fees related to the remedial action. Engineering
design fees include pilot testing, work plan preparation, design of SVE system and
preparation of an implementation plan and permitting. Construction fees include
environmental monitoring and construction observation.
2. 
A 2-year operating period is assumed.
3. 
Excavation areas and volumes based on Table 4-5.
4. 
Cost to excavate includes labor and equipment, excavation support [e.g., sheet
piling] where needed.
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5. 
Excavated soil will be stockpiled in prepared areas (e.g., plywood enclosure with
SVE piping and liner installation). It is assumed that sufficient area is available at
each property.
6. 
Vapor emissions will be treated with Therm-Ox units, if required.
7. 
SVE piping and blower sized for each stockpiled area (2-hp 
blower with and
moisture knockout [skid], temporary enclosure and 100 linear feet of perforated
piping).
8. 
Site restoration includes using treated excavated soil as compacted backfill and
pavement restoration, if required.
9. 
O&M consists of electrical costs for the blowers and Therm-Ox unit. 
Soil
sampling of stockpiled soil (four composite, every 6 months).
10. 
O&M costs:
• 
Soil 
sampling of stockpiled 
soil (assumes eight 
samples/year @
$l,500/sample).
11. 
The estimated cost to install ex-situ SVE at the Curriculum Center and existing
ex-situ at OHenry assumes the treatment system associated with the in-situ SVE
treatment system for bedrock will be used. An additional blower and piping will be
added for the ex-situ treatment. O&M costs associated with air treatment are
included under costs for O&M for in-situ SVE system in bedrock.
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ASSUMPTIONS FOR EQUIPMENT INSTALLATION AND MATERIAL
REPLACEMENT
1. 
Major equipment replacement entails complete replacement of Therm-Ox units at
the Curriculum Center and OHenry dry cleaners.
2. 
Minor equipment entails complete replacement of blower and appurtenances at the
Curriculum Center and OHenry dry cleaners.
GROUNDWATER
General Assumptions (for all properties)
1. 
Administrative and legal fees include filing, contract negotiations, and an allowance
for legal fees related to the remedial action. Engineering design fees include pilot
testing, work plan preparation, design of groundwater collection and treatment
system, and preparation of an implementation plan and permitting. Construction
fees include environmental monitoring and construction observation.
2. 
Separate line items are provided for groundwater source control plans (SCPs) at
Texaco Tutu Service Station and Esso Tutu Service Station. These estimates are
lump sum amounts which represent the total estimated costs of the SCPs (including
engineering design, administrative and legal costs). These estimates are based on
independent consultant estimates taken from SCP designs currently being
formulated; and are included for informational purposes.
3. 
SCPs are assumed to be in operation for 5 years.
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GERAGHTY & MILLER, INC. 
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DESIGN ASSUMPTIONS FOR DEED RESTRICTIONS
1. 
Deed Restrictions for groundwater are as described in GRA 1, and include
estimated costs for filing and application fees.
2. 
The monitoring program assumes sampling and analysis of 15 wells and analyzing
for TCL VOCs, semi-annually.
DESIGN ASSUMPTIONS FOR SITE PREPARATION/MOBILIZATION
1. 
Site preparation, mobilization includes grading for access roads, treatment building,
and access to recovery wells.
DESIGN ASSUMPTIONS FOR WELL DECOMMISSIONING
1. 
Wells will be decommissioned by using locked well seals to prevent use and to
allow access only for sampling.
DESIGN ASSUMPTIONS FOR SITE ACQUISITION
1. 
Cost of property purchase for treatment area, and obtaining right-of-ways for
recovery wells. Property required is assumed to be approximately 0.75 acre.
DESIGN ASSUMPTIONS FOR GROUNDWATER EXTRACTION SYSTEMS
1. 
Recovery well installation includes drilling, material (black steel casing, stainless
steel screen, etc.), well development, and well head enclosure. Depth of wells is
assumed to be 150 feet into bedrock.
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GERAGHTY & MILLER, INC.
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2. 
Cost for piping includes labor and equipment for trenching and backfilling.
Assumes open trench installation. Preliminary piping layouts are mainly beneath
existing roads for easier access approval and implementation. 
Minimal rock
excavation is assumed.
3. 
Well pumps are assumed to be as follows:
• 
GRA 2 (two) 4-hp submersible pumps and appurtenances.
• 
GRA 3 (three) 4-hp submersible pumps and appurtenances.
• 
GRA 4 (five) 4-hp submersible pumps and appurtenances.
DESIGN ASSUMPTIONS FOR GROUNDWATER TREATMENT SYSTEM
1. 
Pre-treatment consists of a chemical sequestering unit for the addition of
orthophosphates with pumps to prevent the deposition of solids in the low-profile
air stripper. Sequestering systems are based on estimated flow rates and include
chemical pumps and piping. Chemical storage is not provided (included in delivery
price) because product is delivered in storage containers.
2. 
The low profile air stripper is assumed to be a tray aeration unit with blower,
controls, and appurtenances. The unit costs are based on vendor quotes, based on
the estimated groundwater quality for each GRA and the estimated flow rate.
Based on the preliminary VOC concentrations, it is assumed one stripper is
sufficient to treat the groundwater.
3. 
The Therm-Ox, if required, is assumed to be a 1,000-scfm unit for GRA 2 and
GRA 3, with fan, controls, and appurtenances. For GRA 4, a 2,000-scfm unit is
assumed with all associated appurtenances. Preliminary calculations indicate that
air treatment associated with the groundwater treatment system is not required for
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any of the GRAs considered. Final design evaluations may vary; therefore, thermal
oxidation for treatment of air discharge is included.
4. 
Liquid phase granular activated carbon (GAC) treatment is provided as a back-up
"polishing unit", in case the air stripper malfunctions. For GRA 2 and GRA 3,
GAC units were assumed to be two 2,000-pound units in parallel, with a
permanent installation. For GRA 4, GAC units are assumed to be configured in the
same manner except 3,000-pound units in parallel would be used. By-pass piping
can be provided to minimize carbon use.
5. 
Process pumps (including standbys) are assumed to be centrifugal pumps rated as
follows
• 
GRA 2 (four) 2-hp pumps, piping and appurtenances.
• 
GRA 3 (four) 2-hp pumps, piping and appurtenances.
• 
GRA 4 (four) 5-hp pumps, piping and appurtenances.
6. 
Discharge pumps (including standbys) are assumed to be vertical turbine pumps
rated as follows:
• 
GRA 2 (two) 2-hp pumps, piping and appurtenances.
• 
GRA 3 (two) 2-hp pumps, piping and appurtenances.
• 
GRA 4 (two) 5-hp pumps, piping and appurtenances.
7. 
The treatment building is sized to accommodate major equipment components of
the treatment facility. The cost includes labor and equipment, and butler type
building set on a poured concrete foundation.
8. 
Lump sum cost for electrical includes an allowance for a Motor Control Center
(MCC), starters, electric service and connections, controls and control panel, leak
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detection and remote dial out. Electrical conduit will go to each well for the
submersible pumps and use the same trench as the extraction piping (no emergency
back up).
9. 
For GRA 2, the POETs are residential size (10 gallons per minute [gpm] max flow
rate), installed with pump and ejector piping. It is assumed that minimal upgrades
to electrical wiring are required.
10. 
It is assumed that water continues to be supplied as it is now, by cisterns or by
trucked water.
O&M Assumptions GRAs
1. 
Electrical costs are for the well pumps, blowers, process and discharge pumps
associated with the treatment units. It also includes an allowance for building
heating and lighting. The following power usage assumptions have been made
utilizing an average price of electricity per kilowatt hour of $ 0.10.
• 
GRA 2 - 29-hp equivalents full time (+/-25 %).
• 
GRA 3 - 33-hp equivalents full time (+/- 25 %).
• 
GRA 4 - 57-hp equivalents full time (+/- 25 %).
2. 
Chemical usage based influent groundwater quality and estimated influent flow
rate, and vendor quotation. Storage is not provided because product is delivered in
storage containers.
3. 
Carbon replacement is assumed to be minimal due to the redundancy provided by
the air stripper. For GRA 2 and GRA 3, one unit changeout every year (2,000 Ibs)
and for GRA 4, one unit changeout every year (3,000 Ibs).
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4. 
Supplemental fuel for Therm-Ox assumed to be propane. 25,000 therms/year at
$LOO/therm is assumed for the 1,000 scfm unit and 38,000 for the 2,000 scfin unit
is assumed.
5. 
For GRA 2, it is assumed the POET systems will use an average of 200 Ibs.
GAC/year.
6. 
System operation assumes one full-time person for the treatment facility effluent
monitoring and POET system monitoring.
7. 
System monitoring is expressed as sampling average annually. It is assumed that
12 samples per year are analyzed for permit compliance monitoring. For POET
systems, one sample per month per installation is assumed, or 60 samples per year.
8. 
O&M costs for the SCPs were provided as lump sum and assumed to operate for
five years.
ASSUMPTIONS FOR EQUIPMENT INSTALLATION AND MATERIAL
REPLACEMENT 
>
1. 
Major equipment replacement entails complete replacement of process equipment
such as air strippers, POETs, GAC units, and Therm-Ox.
2. 
Minor equipment replacement entails replacing pumps and blowers, etc., every 5
years (10 percent of chemical treatment, air stripper, and electrical costs, 5 percent
of groundwater recovery systems [includes well pumps and treatment building]),
50 percent discharge and process pumps and piping).
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APPENDIX P
LIST OF ACRONYMS AND ABBREVIATIONS
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Page 1 of 2
Table D-1. Acronyms and Abbreviations Used, Feasibility Study, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Acronym or
Abbreviation
Meaning
AOC
ARAB
AST
BNAs
BTEX
CERCLA
CG
COCs
DCA
DCCA
1,2-DCE
DNAPL
DPNR
FS
ft/day
GAC
gal/day/ft
gal/day/ft2
GC
gpm
GRA
HI
HQ
HRS
HSL
IRM
LDR
LNAPL
MCL
MCLG
mg/kg
mg/L
MTBE
NCP
PCB
PCE
POET
POTW
ppb
PRG
PRPs
PVC
Administrative Order by Consent.
Applicable or Relevant and Appropriate Requirements.
Aboveground storage tank.
Base/neutral and Acid extractable compounds.
Benzene, toluene, ethylbenzene, and xylenes.
Comprehensive Environmental Response, Compensation and Liability Act.
Cleanup Goal.
Constituents of Concern.
1,1 -dichloroethane.
U.S. Virgin Islands Department of Conservation and Cultural Affairs
(Precursor to DPNR).
1,2-dichloroethene.
Dense non-aqueous phase liquid.
U.S. Virgin Islands Department of Planning and Natural Resources.
Feasibility Study.
Feet per day.
Granular activated carbon.
Gallons per day per foot.
Gallons per day per square foot.
Gas chromatograph (or Chromatography).
Gallons per minute.
Groundwater Remedial Alternative.
Hazard Index.
Hazard Quotient.
Hazardous Ranking System.
Hazardous Substance List.
Interim Remedial Measure.
Land Disposal Restrictions.
Light, non-aqueous phase liquid
Maximum Contaminant Level.
Maximum Contaminant Level Goal.
Milligrams per kilogram.
Milligrams per liter.
Methyl tertiary-butyl ether.
National Contingency Plan.
Polychlorinated biphenyl.
Tetrachloroethene (or perchloroethylene).
Point-of-Entry Treatment.
Publicly-Owned Treatment Works.
Parts per billion.
Preliminary Remedial Goal.
Potentially Responsible Parties.
Polyvinyl chloride.
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Table D-1. Acronyms and Abbreviations Used, Feasibility Study, Tutu Wells Site,
St. Thomas, U.S. Virgin Islands.
Acronym or
Abbreviation
.Meaning
RAL
RAO
RCRA
Rl
RO
RW
SCP
SRA
SSL
SVE
TAL
TAT
TBC
TCA
TCE
TCL
TDS
TEIC
TPH
TSDF
ug/kg
ug/L
USEPA
UST
USVI
VC
VIHA
VOCs
WAPA
Remedial Action Level.
Remedial Action Objective.
Resource Conservation and Recovery Act.
Remedial Investigation.
Reverse osmosis.
Recovery Well.
Source Control Plan.
Soil Remedial Alternative.
Soil Screening Level.
Soil vapor extraction.
Target Analyte List.
Technical Assistance Team.
To-Be-Considered material.
1,1,1 -trichloroethane
Trichloroethene.
Target Compound List.
Total dissolved solids.
Tutu Environmental Investigation Committee.
Total petroleum hydrocarbons.
Treatment, Storage, and/or Disposal Facility.
Micrograms per kilogram.
Micrograms per liter.
U.S. Environmental Protection Agency.
Underground storage tank.
U.S. Virgin Islands.
Vinyl chloride.
Virgin Islands Housing Authority.
Volatile organic compounds.
Water and Power Authority.
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