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DEPARTMENT OF THE INTERIOR

UNITED STATES GEOLOGICAL SURVEY



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Prepared in cooperation with the

WATER RESOURCES RESEARCH INSTITUTE OF THE COLLEGE OF THE VIRGIN ISLANDS



GEOLOGICAL SURVEY, WRD

OPEN-FILE DATA REPORT 84-807



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RECONNAISSANCE OF GROUND-WATER QUALITY

IN THE U.S. VIRGIN ISLANDS, JULY 1984



UNITED STATES GEOLOGICAL SURVEY

WATER RESOURCES DIVISION

OPEN-FILE DATA REPORT 84-807



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SELES

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Prepared in cooperation with the

WATER RESOURCES RESEARCH INSTITUTE

OF THE COLLEGE OF THE VIRGIN ISLANDS



1984



RECONNAISSANCE OF GROUND-WATER QUALITY

IN THE U.S. VIRGIN ISLANDS, JULY 1984



By

Rene Garcia and Michael Canoy



INTRODUCTION



The demand for ground water in the U. S. Virgin

Islands, specially for domestic use has increased marked-

ly in recent years. In 1982, ground water withdrawals

for public and domestic use in the U.S. Virgin Islands

were about 1.1 million gallons per day (Torres and

Dacosta;, 1984). Recent investigations show that addi-

tional withdrawals might be possible (F. G6dmez-Godmez,

USGS personal commun., 1984).



In spite of increasing demands for ground water,

data on its quality is very scarce. The lack of data

constitutes a major gap in the knowledge of the U.S.

Virgin Islands' hydrologic environment. There are no

active water-quality monitoring networks and the most

recent reconnaissance was conducted nearly two decades

ago (Cosner, 1972; Jordan, 1975; Jordan and Cosner, 1973;



bi 5 L972)

‘ GEOLOGICAL re ison )



Bete Va, Loa In 1984, the U.S, Geological Survey, Water Resources

F 95 Division, conducted a reconnaissance of the ground-water

EB 2 1985 qu%lity at selected wells throughout the U.S. Virgin



/ fuer



Islands Cities 1). The investigation was conducted in



“cooperation with the Water Resources Research Institute

of the College of the Virgin Islands. Wells representing

the principal aquifers (fig. 2 and tables 1 to 5), were

sampled for physical, chemical and bacteriological

characteristics. Selected wells were also sampled to

determine potential contamination with priority pollutants

as designated by the U.S. Environmental Protection Agency

(EPA). This report summarizes the data collected during

the investigation (July 1984). The data will provide a

base line for future investigations and an assessment of

water use versus quality.



We wish to thank the U.S. National Parks Service,

Public Works Department in St. Croix and St. John, and

the Director of Conservation and Cultural Affairs in St.

Thomas for their assistance.



%



67°00’ 6600' 65°00’

T : i u T

ATLANTIC OCEAN

18°30’

ST. THOMAS

PUERTO RICO Culebra ST. JOHN

U.S.

18°00’ Wiegues VIRGIN

ISLANDS

CARIBBEAN SEA

ST. CROIX

) 10 20 30 40 MILES

17°30’ :

| i] i f



Figure 1.--Geographic location of the U.S. Virgin Islands.



Table 1.--Physical, chemical, and bacteriological characteristics from selected wells in the U.S. Virgin



Islands, July 1984.



WELL || LOCATION OPERATED] DWL T ve pH

METHODS AND PROCEDURES al Kee (LAT/LONG) WEE oe BY (FT) (DEG C) — (UNITS) a oa es — eee one i

Nineteen wells in the U.S. Virgin Islands (fig. 2 1 | 176245644758 Golden Grove no. 1 OPW 36.75 29.0 1725 7.4 574 K 8 1 0.255 Ce 750 0.040 i

and tables 1 to 5), were sampled as follows: eight wells 2 174308646841 Adventure no. 16 DPW 40.74 33.0 1759 7.6 531 <1 ee 2190 710 2014 3.

in St. Croix (map numbers 1 to 8), seven wells in St. 3 174258645222 Prosperity no. 1 DPw 34.82 28.5 9325 7.0 316 <4 K & C25 14 «0901 ue

Thomas (map numbers 9 to 15), and four wells in St. John 4 174329644547 Barren Spot now 5 OPW 70.96 27.5 3175 7.6 597 <1 K 2 C16 1.0 2915 °

(map numbers 16 to 19). The wells were selected to 5 1742256464719 Fairplains no. 6 CPW 58.07 a 5759 7.0 489 <4 <4 016 » 687 - 071 °

represent the most important pumping centers. The

samples were collected as close as possible to the well 6 174527644601 Concordia noe 1 DPW 235227 27.5 2975 70 458 < 4 40 e045 (er 10 2013 a?

casing. Methods described by Classen (1982), were used 7 4746596464716 Rust-up-twist PO 32.13 27.0 2550 704 590 K 4 5800 030 2850 «052 an

for the collection of the samples. 8 174526643713 Zell’s well PO 78.93 32.25 4675 7.2 446 38 23c0 2016 2940 2014 <a

9 182033645312 VeITeHeA. now 2 VIHA 73.84 29.0 1150 Ae 602 1 65 2008 ND -909 Net

Temperature, specific conductance, pH and total 10 181913645307 Bavoni noe 2 PO 240357 28.5 2359 722 554 < 1 370 2011 &.0 2309 224

alkalinity of the samples were measured at each site

immediately upon collection of the samples. The depth of 11 182036645813 CoVoI. now 2 CVI 46.83 29.0 1250 724 485 1 3% -007 5.8 2011 +24

the water level below land surface was also determined. 412 182141645746 Agriculture Station USCA 65.15 25-5 1909 7 es 448 1 23 »CO9 A ot 2054 Tiel)

Samples for chemical analysis of trace elements, common 13 181945645257 Polycarib no. 3 PO 118.27 28.6 2425 Tue 580 1 K 488 -016 2.3 -003 3.3

ions and nutrients were collected, filtered, and 14 182130645745 Bryan”’s Well now 2 PO ND 25.5 1250 6.9 251 K 36 4 C06 2.8 065 «7

preserved in accordance with procedures described by 415 182142645427 Mohagony Run now? PO 81.70 28.0 2230 6.8 580 <4 4700 < 2007 < .010 <.001 2.0

Skougstad and others (1979), and Goerlitz and Brown

(1972). Samples for the determination of priority 16 182112644519 NePeSe NOe 9 USNPS ND 27.0 1925 6.8 518 < 1 10 e005 «597 - 009? 1.2

pollutants were collected at five wells (map numbers 4, 17 18205 3644322 Carolina well DPW 5.82 2fe5 2009 6.8 287 6 109 ef08 vee a0V2 Tare

ame Pe <2 and 19), and preserved in accordance with 18 182010644728 NaPeSe NOe 2 USNPS 2715 29.0 25¢C0 7.0 560 30 3900 a017 4.9 2012 2.0

methods established by Brown and others (1970). The 19 182043644546 Sussanaberg no. 5 DPW 62.389 25.5 1459 720 538 5 8 < 001 qials 2007 127

samples were shipped to the U.S. Geological Survey

National Water-Quality Laboratory in Doraville, Georgia, E xX P L A N A T I Oo N



for chemical analyses. Determinations of fecai coliform

and fecal streptococci bacteria were completed from raw

water samples using the membrane filter method (Greeson

and others, 1977). Processing and incubation of the

samples were begun in the field shortly after collection.



RESULTS



Results of the field and laboratory determinations



DWL - Depth to water level below land surfaces in feet



J - Temperatures in degrees Celsius

SC - Specific conductance.



in micromhos per centimeter at 25°C



ALK - Total alkalinity as calcium carbonates in milligrams per liter

FC - Fecal coliform bacterias in colonies per 100 millilitars

FS ~- Fecal streptococci bacterias in colonies per 100 milliliters



DPW - Virgin Islands Department of Public Works

VIHA - Virgin Islands Housing Authority

USDA - United States Department of Agriculture



NO2 -

NO2 +

PO4 -

TOC -

TOS -

PO -

cvI -

USNPS



Nitrite as nitrogens total



NO3 - Nitrite plus nitrate as nitrogens total/ mitigrams

Phosphorusv orthophcsphate per liter

Organic carbone total



Total dissolved solids



No data



Privately operated



College of the Virgin Islands



- United States National Park Service



are shown in tables 1 to 5. The principal findings of

the reconnaissance were as follows:



1. Specific conductance values normally ranged

from 1,400 to 3,000 micromhos per centimeter

(umhos/cm). Well numbers 6 and 9 had values which

surpassed 4,500 umhos/cm.



2. Fecal coliform and fecal streptococci bacteria

were detected in samples from 18 of the 19 wells

sampled. Colony counts of fecal streptococci

bacteria were as high as 5,800 colonies/100 milli-

liters (mL) of raw water sampled.



3. Nitrate concentrations exceeded 1.0 milligrams

per liter (mg/L) at ten of the wells sampled.



4, Chloride concentrations generally ranged from

180 to 600 mg/L. At 13 wells (map numbers 1, 4, 5

tone gos LO, 12° v3, 15, 17, .and 18)3 chiloride

concentrations exceeded drinking water standards of

250 mg/L (EPA Drinking Water Regulations).



5. Sulfate concentrations for most wells were less

than the drinking water standard of 250 mg/L. All

the wells sampled had total dissolved solids

exceeding the EPA secondary drinking water standard

of 500 mg/L.



6. Concentrations of organic compounds and most

trace elements at selected sites were less than

detection limits.



Additional information about the wells sampled and

the data in this report is available from the U.S.

Geological Survey, Water Resources Division, Caribbean



District office in San Juan, Puerto Rico (Tel. (809)

753-4414).

B50 08 SE pO8 Js 64° 50’

|

18°24'}— S Sy ~

ST. THOMAS pa

18°201— na

Q.1 2 9 4mites de

| | | |



COASTAL EMBAYMENT



Ki



PRI



SAMPLED WELL SITE



17°45’



17°40’



EXPLANATION



18°22"



AQUIFER



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VOLCANIC ROCKS

AQUIFER



NGSHILL AQUIFER

o'8

WELL SITE

@'?



ORITY POLLUTANTS 18°18'



se eo Sa538



ST. CROIX



0 1 2 3 4 MILES

eS) aes ea La



Figure 2.--Principal aquifers and selected wells sampled in the U.S. Virgin Islands.



Table 2.--Concentrations of dissolved common ions and trace elements from selected wells in the U.S. Virgin Islands, July 1984.



COMMON IONS, DISSOLVED TRACE METALS, TOTAL

WELL (MILLIGRAMS PER LITER) (MICROGRAMS PER LITER)

INUMBER



ON MAP| Ca Mg Na K $04 Cl F sid2 TDS As Ba Cd Cr Pb Hg Se Ag



4 67 48 280 0.9 99 270 0.6 4&7 1159 2 4100 1 2 2 a ees 3 <1



Pid 37 36 250 =? 55 190 =O 38 919 2 < 100 1 2 2 0.6 2 <4



3 400 29 92 eg 33 170 oo 37 610 2 106 1 6 2 0.5 4 Soon



4 21 10 5990 8.0 170 460 <0 28 1640 = == a — —— == <a =e



5 220 10 750 MATE 270 1500 <2 40 3190 2 200 1 2 1 0.6 4 1



6 120 65 420 624 190 600 Pr) 36 1670 == = <= == == zai ce a ie



A 55 42 440 4.5 55 490 8 38 1390 4 < 100 1 <1 1 0.4 1 <4



8 120 81 679 mie 220 1100 Pe 33 2460 A < 100 <1 < 14 <4 124 8 <1



9 71 46 230 1.4 €1 160 28 45 977 1 < 100 1 5 S < - O54 2 Sit



10 66 83 340 ceo 99 440 =o 46 1410 4 < 100 41 5 1 0.2 3 <4



11 39 32 230 29 44 180 28 48 861 41 < 700 4 4 1 0-5 3 <4



12 37 24 339 28 72 330 5) 34 4090 4 <€ 100 1 3 < 4 Uys 2 <4



13 40 43 370 129 90 410 at 2? 1320 << oe == ee ca = = ——



14 16 13 220 «8 32 230 ae 35 696 1 < 100 q 4 4 0-5 4 <4



15 180 62 289 6.9 200 390 1.1 33 1460 == == == == == =< —— ==



16 77 64 230 3.3 42 370 aS 36 1120 1 < 190 u 4 1 0.4 1 <4



a 41 46 2990 Sat 120 430 aS 36 1140 4 < 10C 2 5 <1 Uses 1 <4



18 100 TS 360 2e2 67 490 a5 38 1460 1 < 100 Ps 6 1 0.6 |< 1 <1



19 66 54 180 See 30 130 =o 40 859 == =—— = —— == iar oo =



E X P L A N A i I Oo N

Ca - Calciun K ~- Potassium F - fluoride As ~ Arsenic Cr - Chromium Se - Selenium

Mg ~- Magnesium $04 - Sulfate $iG2 - Silica Ba - Barium Ph - Lead Ag - Silver

Na ~- Sodium Ci - Chloride TOS - Total dissolved solids Cd - Cadmium Hg - Mercury == ~ No data

Table 3.--Concentrations of priority pollutants at selected wells in the U.S. Virgin Islands, July 1984.

NUMBER Al Sb As Be Cd cr Cu Fe Pb Li Mn Hg Mo Ni Se Ag Zn CYANIDE

ON MAP

01

4 790 <1 2 < 10 <4 < 16 <9 < 10 4 10 < 10 0.1 2 7 ee | 4 nie 10 < Os

Y \<- 170 <1 <4 < 10 <4 < 10 <4 10 2 50 5 ae |e 8 a <4 2 6 <1 10 <4 04

14 10 | -- £65 1.22 -- 11 Tar | & 410 <4 180 -- < 10 -- -- 2 13 < 2041

16 19 4 -- <a 1.5 -- <4 5 236 < 10 < 4 17 == < 10 —— sist 1 190 < 04

19 20 <4 x4 < 10 S19 < 10 5 | < 10 q <4 <-96 | ae | 1 4 < 4 21 < .01

E xX P L A N A T | Oo N



Cu ~ Copper

Fe - Iron

Pb - Lead



Be ~ Beryllium

Cd - Cadmium

Cr ~- Chromium



Al - Aluminum

Sb ~- Antimony

As ~ Arsenic



Concentrations in micrograms per liter

Li - Lithium

Mn - Manganese

Hg ~ Mercury



Mo

Ni

Se



Concentrations in milligrams per liter

Cyanide



Ag - Silver

in - Zinc

-- - No data



- Molybdenum

- Nickel

- Selenium at



Table 4.-- Purgeable organic, base-neutral, and acid extractable compounds for which analyses were performed

in samples from five wells in the U.S. Virgin Islands, July 1984.



173-Dichlorepropene

Ethylbenzene

Methylbromide

Methylene chloride



2-Chloroethyl vinyl ether

Chloroform

Dibromochloromethane

Dichlorobromomethane

Jichlorodifluoromethane



Benzene 101-Dichloroethane

Bromoform 1/2-Dichloroethane



Carbon tetrachlorice 17/1-Dichloroethylene

Chlorobenzene 17/2-trans~Dichloroethylene

Chloroethane 1/2-Dichloropropane



Tetrachloroethylene



Tol



1Ieieinmtrichloroethane

Ivis2-Trichloroethane

Trichloroethylene



Trichlorofluoromethane

Vinyl chloride



Ieie2e2-Tetrachloroethane



Minimum detection limit 3.0 micrograms per liter



uene



Benzo (b) fluoranthene 104~Dichlorobenzene

B3enzo (k) flucroanthene Diethyl phthalate



Benzo (€grehei)d perylene Dimethyl phthalate

Benzo (Ca) pyrene Di-n-butyl phthalat



2724-Dinitrotoluene

206~Dinitrotoluene



4~Bromophenyl phenyl ether

Butyl benzyl phthalate



bis (2-Chloroethoxy) methane Di-n-octylphthalate

bis €2-Chlorethyl) ether



bis (2-Chloroisopropyl) ether

2-Chioronaphthalene

4-Chlorophenyl phenyl ether



Fluoranthene

Flucorene

Hexachlorobenzene



Acenapthene Chrysene



Acenapthylene Dibenzo (ash) anthracene

Anthracene 172-Dichlorobenzene

Benzo (a) anthracene 173~-Dichlorobenzene



e



bis C2-Ethylhexyl)phthalate



Hexachlorobutadiene

Hexachlorocyclopentadiene



Hexachloroethane 476-Dinitro~2-methylohenol

Indeno (12/3) pyrene 24-Dinitrophenol

Isophorone 2~“Nitrophenol

Naphthalene 4-Nitrophenol

Nitrobenzene Pentachlorophenol



Phenol



n-Nitrosodi-n~propylamine

n-Nitrosodimethylamine

n-Nitrosodiphenylamine



Phenanthrene

Pyrene

1e2e4-Trichlorobenzene

4-Chlioro-3-methylehenol

2-Chlophenol



Minimum detection limit 1.0 micrograms per liter



274-Dichlorophenol

204-Dimethylphenol



204e4-Trichlorophenol

2e3e7r8-Tetrachlorophenol



4-8romophenyl phenol

373-Dichlorobenzid



All concentrations were below minimum detection level.



Table 5. Organochlorine insecticides, polychlorinated byphenils,

and polychlorinated naphthalenes for which analyses were

performed in samples from five wells in the

U.S. Virgin Islands, July 1984.



Minimum detection level 0.01 micrograms per liter



ALDRIN

dDD



DDE



ODT

OIELDRIN



ENDRIN



ENDOSULFAN

HEPTACHLOR

HEPTACHLOR EPOXIDE

LINDANE



METHOXYCHLOR

MIREX



Minimum detection level 0.1 micrograms per liter



CHLORDANE



GROSS POLYCHLCRINATED BIPHYNELS CAS PCB)

GROSS POLYCHLORINATED NAPHTHALENES CAS PCN)

AROCHLOR 1016



AROCHLOR 1221



AROCHLOR

AROCHLOR

AROCHLOR

AROCHLOR

AROCHLOR



1232

1242

1248

1254

1269



PERTHANE



Minimum detection level 1.0 micrograms per liter



TOXAPHENE



All concentrations were below minimum detection level.



REFERENCES



Brown, E., and others, 1970, Methods for the collection

and analysis of water samples for dissolved minerals

and gases: U.S. Geological Survey Techniques of

Water Resources Investigations, Book 5, Chapter Al,

160 p.



Classen, H.C., 1982, Guidelines and techniques for

obtaining water samples that accurately represent

the water chemistry of an aquifer: U.S. Geological

Survey Open-File Report 82-1024, 49 p.



Cosner, O.J., 1972, Water in St. John, U.S. Virgin

Islands: U.S. Geological Survey Open-File Report,

(unnumbered).



Goerlitz, D.F., and Brown, E., 1972, Methods for analysis

organic substances in water: U.S. Geological

Survey, Techniques of Water Resources

Investigations, Book 5, Chapter A3, 40 p.



Greeson, P.E., and others, 1977, Methods for collection

and aquatic biological and microbiological samples:

U.S. Geological Survey, Techniques of Water

Resources Investigations, Book 5, Chapter A4, 332 p.



Jordan, D.G., 1975, A survey of the water resources of

St. Croix, U.S. Virgin Islands: U.S. Geological

Survey Open-File Report, (unnumbered), 51 p.



Jordan, D.G., and Cosner, 0.J., 1973, A survey of the

water resources of St. Thomas, U.S. Virgin Islands:

U.S. Geological Survey Open-File Report, (unnumber-

ed), 55 p.



Robison, T.M., and others, 1972, Water records of the

U.S. Virgin Islands, 1962-69: U.S. Geological

Survey Open-File Data Report, 163 p.



Skougstad, M.W., and others, 1979, Methods for

determinations of inorganic substances in water

and fluvial sediments: U.S. Geological Survey,

Techniques of Water Resources Investigations,

Book 5, Chapter Al, 626 p.



The National Drinking Council, 1977, Drinking water

and Health: National Academy of Sciences,

Washington, D.C., 1977, 939 p.



Torres, H., and Dacosta, R., 1984, Estimated water use in

St. Thomas, U.S. Virgin Islands, July 1983 to June

1984, U.S. Geological Survey Open-File Data Report

84-721, 1 pl.



- Environmental Protection Agency, Drinking Water

Regulations: 40 C.F.R., Part 141.



TECHNICAL REPORT NO. 20

CARIBBEAN RESEARCH INSTITUTE

COLLEGE OF THE VIRGIN ISLANDS



ST. THOMAS- U.S.VIRGIN ISLANDS 00802



PROJECT NO. 375003

AGREEMENT NO. 14-08-0001-G-875



THE RESEARCH ON WHICH THIS REPORT IS BASED

WAS FINANCED IN PART BY THE UNITED STATES

DEPARTMENT OF THE INTERIOR AS AUTHORIZED

BY THE WATER RESEARCH AND DEVELOPMENT ACT

OF 1978 (Pil. 950467).



U.S. GEOLOGICAL SURVEY

WATER RESOURCES DIVISION



CARIBBEAN DISTRICT

SAN JUAN, PUERTO RICO