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SDMS Document 
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GOVERNMENT OF THE VIRGIN ISLANDS OF THE UNITED STATES 
Department of Planning <b /Natural Resources 
Division of Environmental Proiectiort 
WATER GUT HOMES 1118 
B-111/APT, 14-A 
CHBI3TIANSTED. ST. CROIX 00820-5065 
(340) 773-0565 
January 26.2001 
Ms. Caroline Kwan 
Remedial Project Manager 
U.S. Environmental Protection Agency, Region II 
290 Broadway, 20th Floor 
New York, NY 10007-1866 
RE: 
Virgin Islands Chemical Superfund Site 
St. Croix, USVI 
Comments on the Final Draft Feasibility Study Report 
Dear Ms. Kwan: 
The Department of Planning and Natural Resources (DPNR) has reviewed the 
Final Draft Feasibility Report (Final Draft FS) for the Virgin Islands 
Chemical Superfiind Site and is forwarding the following comments. 
Estimated Cleanup Times 
The Draft Final FS assumes cleanup to MCLs in 3 to 4 years. Page 48 contains 
the following paragraph: 
"Although the minimum estimated cleanup times (3-4 years) for both Areas are 
relatively shon, the presence of geologic heterogeneities in both the AST 
and FPP Areas, as well as the presence of significant source mass above the 
water table in the AST area, could extend the estimated cleanup time by 
anywhere from a few years to more than 100 yeais and render the cleanup time 
predictions highly uncertain (National Academy Press, 1994)" 
DPNR finds this important paragraph in need of fiirther discussion and 
explanation regarding the source of this quote and how the authors of this 
paragraph calculate the estimated time for cleanup to MCLs. 
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Geo-Hydrology 
DPNR is concenied that the entire Final Draft FS is flawed based on a 
fundamental misinterpretation ofthe site and area geo-hydrology. 
The Report describes two upper aquifers in the alluvium (sands, gravels and 
clays) layer. The authors seem to be unable to differentiate between 
unconsolidated materials in the Gut (which are typically unsaturated) and the 
fractured marly limestone ofthe Kingshill Marl (aquifer). The 
fractures in the marl are the water produdng zones while groundwater 
recharge ofthe marl occurs in the guts through the unconsolidated material 
above. 
The United States Geological Survey (USGS) has performed exhaustive studies 
ofthe Kingshill Aquifer in South Central St. Croix, including the aquifer in 
the area around the study site. The USGS describes the area as having 10 to 
60 feet of alluvium (unconsolidated material) overlaying the Kingshill Marl 
(water bearing formation). The Final Draft FS describes the deeper zones of 
the alluvium as "exhibiting confined to semi-confined conditions". DPNR is 
unaware of any scientific or environmental study describing area conditions 
ofthe Kingshill Aquifer in the study area as "confmed or semi-confined". 
The USGS describes the Kingshill Aquifer as a "single, unconfmed, 
hydrologically connected unit" (or 1 single aquifer), meaning water flows 
between the units without restriction. Typically loose material (alluvium) 
is 10-60 foct thick overlaying marly fractured limestone finom 50-100 feet 
below that. The aquifer is usually not any deeper than 120 feet. Generally, 
south ofthe highway, the post- Kingshill limestone predominates (highly 
transmissive). 
Desaibing "area* geo-hydrology as "two upper aquifers under confined to 
semi-confined conditions'* is misleading and dramatically affects all ensuing 
risk assessments, the evaluation ofthe efficacy ofthe proposed treatment 
system and clean up duration estimates. DPNR is not satisfied with an FS 
based on a mischaracterization of tlie aquifer and will not accept a theory 
that is so drastically opposed to long-standing and documented 
investigations. DPNR urges EPA not to accept this two-aquifer theory or 
the implications it may have regarding tbe remedial plans/timeline. 
Due to the multiple consultants historical misunderstanding/mischaracterization 
of area hydrology, DPNR believes il is essential to rewrite this section on 
area/site hydrology to reflect the well-documented and scientifically accurate 
description of area hydrology including, the USGS description ofthe aquifer 
and area/regional conditions. It is inconceivable that USGS publications on 
the subject would not be referenced in any ofthe reports produced during 
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the site investigation and leading up to the FS. 
Specific borehole conditions should be described as such but should not 
be used to describe the "area aquifer" or to infer conditions beyond the 
immediate borehole location. Cunent descriptions ofthe site and area are 
misleading and leaves the reader with the impression that vertical 
groundwater/contamination movement is nearly impossible due to the 
inaccurate "two aquifer" scenario. 
Additional review and comments will be forthcoming on the specifics of 
anaerobic and aerobic degradation of contaminants at the site, remediation 
time frames and the risk assessment. 
In general the Department is disturbed by the tendency ofthe rqxjrt to 
underestimate potential for lateral and vertical migration and to minimize 
the potential for off-site migration. 
We appreciate your consideration of our comments. If you should have any 
additional questions, please give me a call. 
5yed Syeddli. P.G. 
Project Manager-DEP/DPNR 
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