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Halliburton Company FIELD INVESTIGATION TEAM ACTIVITIES AT UNCONTROLLED HAZARDOUS SUBSTANCES FACILITIES - ZONE I NUS CORPORATION SUPERFUND DIVISION *64413* 64413 02-8902-44-PA REV. NO. 0 FINAL DRAFT PRELIMINARY ASSESSMENT LAGA BUILDING/VIRGIN ISLANDS DEPARTMENT OF EDUCATION ST. THOMAS, U.S. VIRGIN ISLANDS PREPARED UNDER TECHNICAL DIRECTIVE DOCUMENT NO. 02-8902-44 CONTRACT NO. 68-01 -7346 FOR THE ENVIRONMENTAL SERVICES DIVISION U.S. ENVIRONMENTAL PROTECTION AGENCY MARCH 24,1989 NUS CORPORATION SUPERFUND DIVISION SUBMITTED BY: DIANETRUBE PROJECT MANAGER REVIEWED/APPROVED BY: JOSjEPHMAYO ^ RONALD M. NAMAN SITE MANAGER FIT OFFICE MANAGER 02-8902-44-PA Rev. No. 0 POTENTIAL HAZARDOUS WASTE SITE PRELIMINARY ASSESSMENT PART I: SITE INFORMATION 1. 2. 3 4. 5. Site Name/Alias Laqa Building/Virgin Islands Department of Education Street Route 38. Tutu District_________ ________ State U.S.V.I._____ Zip 00802 _ Cong. Dist. NA City Tutu District County NA ERA ID No. New Site County Code NA Latitude 18" 20'37" N. Longitude 64° 53' 10"W. USGS Quad. Eastern St. Thomas. U.S. Virgin Islands Owner Virgin Islands Dept. of Education Street Route 38. Tutu District_________ City St. Thomas___________________ 0 pe rator Sa m e as a bo ve____________ Street____________________ City_____________________ Type of Ownership D Private Q Federal [ D County n Municipal [ Owner/Operator Notification on File D RCRA 3001 Date ______ [x] None n Unknown Tel. NO. 809-774-2183 State U.S. Virgin Islands Zip 00802 Tel. No. ___ ________ State Zip. State Unknown ICERCLA103C [x] Other U.S.V.I. Deptof Education Date 9. Permit Information Permit Permit No. None Date Issued Expiration Date Comments 10. Site Status [x] Active 11. Years of Operation |nactive Unknown to Unknown Present 02-8902-44-PA Rev. No 0 12. Identify the types of waste units (e.g., landfill, surface impoundment, piles, stained soil, above- or below-ground tanks or containers, land treatment, etc.) on site. Initiate as many waste unit numbers as needed to identify all waste sources on site. (a) Waste Management Areas Waste Unit No. Waste Unit Type Facility Name for Unit 1 Drums Drums behind Laqa Building_____ (b) Other Areas of Concern Identify any miscellaneous spills, dumping, etc. on site; describe the materials and identify their locations on site. No other spills, incidents of dumping, etc, were observed on the site during the NUS Corp. Region 2 FIT on-site reconnaissance on 2/15/89.___________________________ 13. Information available from Contact Amy Brochu_______ Agency U.S. EPA________ Tel. No. (201)906-6802 Preparer Joseph Mayo______ Agency NUS Corp. Region 2 FIT Date 3/31/89______ 02-8902-44-PA Rev. No. 0 PART II: WASTE SOURCE INFORMATION For each of the waste units identified in Part I, complete the following six items. Waste Unit 1 - ____Drums______, Drums behind Laqa Building____ 1. Identify the RCRA status and permit history, if applicable, and the age of the waste unit. There are no known current or previous RCRA permits for the Laga Building site. The age of the waste unit is unknown. 2. Describe the location of the waste unit and identify clearly on the site map. The drums are located less than 100 feet northwest of the northwest corner of the Laga Building. 3. Identify the size or quantity of the waste unit (e.g., area or volume of a landfill or surface impoundment, number and capacity of drums or tanks). Specify the quantity of hazardous substances in the waste unit. Twenty-two drums were visible in the brush behind the Laga Building. The area where the drums are located is overgrown with thick brush. The drums were deposited in an uncontrolled manner; some were on their sides, and some were corroded and empty. At least one was full. Twenty-one of the drums were steel and one was plastic. All of the drums in the disposal area had capacities of 55 gallons each. 4. Identify the physical state(s) of the waste type(s) as disposed of in the waste unit. The physical state(s) should be categorized as follows: solid, powder or fines, sludge, slurry, liquid, or gas. At least one of the drums in the waste unit contained liquid. The physical state of the waste in the remaining drums is unknown. 5. Identify specific hazardous substance(s) known or suspected to be present in the waste unit. No specific hazardous substances are known to be present in the waste unit. The Virgin Islands Department of Planning and Natural Resources (DPNR) indicated that prior to ownership by the Department of Education, the Laga Building was a textile facility which used solvents in textile processing. 6. Describe the containment of the waste unit as it relates to contaminant migration via groundwater, surface water, and air. There is essentially no containment of the waste unit. Drums are deposited in a haphazard manner; some are on their sides and some are badly corroded. There are no containment structures associated with the drums; therefore, the potential exists for waste in the unmaintained and corroding drums to be released to the environment and transported to groundwater and surface water. Ref. Nos. 1.20_________ ___ 02-8902-44-PA Rev. No. 0 PART III: HAZARD ASSESSMENT GROUNDWATER ROUTE 1. Describe the likelihood of a release of contaminant(s) to the groundwater as follows: observed, alleged, potential, or none. Identify the contaminant(s) detected or suspected, and provide a rationale for attributing the contaminant(s) to the facility. The potential exists for contaminants to be released to groundwater. The drums are deposited in a haphazard manner, and some are corroded through. There are no containment structures surrounding the drums to prevent a release of the contents to the environment. The drums have not been sampled and there is no historical information that indicates what their contents were. The DPNR indicated that the Laga Building was a former textile processing facility that used solvents in its processes. Ref. No. 1 2. Describe the aquifer of concern; include information such as depth, thickness, geologic composition, permeability, overlying strata, confining layers, interconnections, discontinuities, depth to water table, groundwater flow direction. The rock units of St. Thomas and St. John are divided into three major groups: the Water Island Formation, the Virgin Island Group, and an unnamed group of dioritic plutons. The Water Island Formation, which is late lower Cretaceous in age, consists of keratophyre and spillates. The Virgin Island Group, which is probably early Cretaceous or Albian in age, consists of andesitic-pyroclastic rocks and sedimentary formations. The Virgin Island Group is divided into four formations: the Louisenhoj Formation, which consists of augite-andesite breccia, tuff, and conglomerate; the Outer Brass Limestone, which consists of partially silicified- tuffaceous-radiolarian-limestone; the Tutu Formation, which consists of tuffaceous wacke, including megabreccia near the base and limestone near the top; the Hans Lollik Formation, which may be Eocene in age and consists of augite-andesite breccia and tuff. The final group is made up of one or more dioritic plutons. These unamed dikes and plugs of quartz-andesine hornblende porphory are Upper Cretaceous and Lower Tertiary in age. Alluvian deposits are quaternary in age. The Water Island Formation, which consists of 95 percent volcanic flow breccias, was probably extruded on a relatively level ocean floor The absence of terrigenous sediments from this formation indicates that there were no emergent islands present in the area at the time of extrusion. Emergent islands would have served as a source of weather sediments or detritus, which are not present in this formation. There is evidence that sea floor subsidence occurred during the greater part of the accumulation of this formation. However, the subsidence was not rapid enough to maintain a constant water level, thereby causing explosive eruptions near the top of the formation. Regional uplift occurred near the end of the Water Island. The Louisenhoj Formation of the Virgin Island Group unconformably overlies the Water Island Formation and crops out on about half of the land area on St. Thomas. Pillsbury Sound between St. Thomas and St. John was the origin of this formation. Evidence of this center is based upon the coarseness of volcanic ejecta in the formation in nearby eastern St. Thomas and western St. John. Material is less coarse and tuffs are more predominant as one moves further east and west away from the center or origin. This augite-andesite formation ranges in thickness from 4,000 to 13,000 feet. In certain areas of St. Thomas and St. John conglomerates are interbedded with andesitic rocks at the base of this formation. The depositional environment of this conglomerate varies from location to location throughout this formation. The Outer Brass Formation of the Virgin Island Group is mostly siliceous limestone which overlies the Louisenhoj Formation. This limestone formation is an offshore deposit formed by radiolarian and foraminiferal remains including a minor amount of tuff. Thicknesses are known to be at least 600 feet TUT 02-8902-44-PA Rev. No 0 Overlying the Outer Brass Formation is the Tutu Formation. The Tutu Formation is fine- to coarse-grained volcanic wackes, which are termed flysch. This formation is derived from eroding sediments from the Louisenhoj andesites. Exposed thicknesses are known to be as much as 6000 feet. Within this formation is a megabreccia lithofacies with an average thickness of 30 feet, and a limestone member with thickness up to 300 feet. The Hans Lollik Formation, which consists of at least 10,000 feet of augite-andesite pyroclastic rocks, crops out on Little Hans Lollik Island. Dioritic plutons are located in Pillsbury Sound between St. Thomas and St. John; in the narrows, between St. John and the British Virgin Islands; and south of St. Thomas. The exact delineation of these plutons is uncertain. Throughout the islands isolated dikes of quartz-andesine porphyries, andesine-hornblende porphyries, lamprophyres, breccias, and pegmatites appear. Folding occurred after the deposition of the Virgin Island Group. Rocks were tilted to form a northward-dipping homocline, which is cut by sets of faults trending N 45°W, N 55°E, and north. Well-defined joint sets parallel each of the major fault trends. Dips range from 15° to 90° with the average being 40°. Strike-slip faults have horizontal offsets of less than 1 mile. Two major strike-slip graben structures or fault systems exist. The first passes through Redhook, St. Thomas, and the eastern tip of Lovango Cay. The second crosses St. John, from Contact Point on the southwest to Brown's Bay on the northeast. Most recent Pleistocene to Holocene alluvial deposits occurred primarily in coastal embayments. However, a narrow bank of alluvium extends up to Turpentine Run on the east end of the island. Most of these deposits are composed of silt, clay, and thin, discontinuous beds of sand and gravel. Maximum thickness of these is 50 feet. Groundwater movement is limited to openings and joints along fault zones. Regional geologic information is insufficient to determine whether these fractures and fault zones are present in all of the above-described formations; however, for this report it is assumed that the fractures and fault zones are present in all of these formations. The valleys on the island are the result of weak zones caused by faulting and jointing and are primary recharge areas for groundwater. Alluvial deposits have a high porosity but low permeability, making this aquifer unfavorable for groundwater production. In coastal embankments throughout the island, saltwater intrusion is widespread in alluvial deposits. In most areas, alluvial deposits are interconnected with bedrock and act to recharge precipitation to the underlying bedrock. The direction of groundwater flow in the Turpentine Run Basin Aquifer is south-southeast which is generally along the direction of flow of Turpentine Run. Depth to groundwater in the aquifer ranges from 5 to 60 feet, and the altitude of the water levels ranges from 1 to 209 feet above mean sea level. Ref. Nos. 11, 16 3. Is a designated sole source aquifer within 3 miles of the site? There are no sole source aquifers, as designated in the Federal Register, within 3 miles of the site. Ref. No. 8 4. What is the depth from the lowest point of waste disposal/storage to the highest seasonal level of the saturated zone of the aquifer of concern? Drums in the waste unit were deposited on the ground surface. Depth to groundwater in Virgin Island Housing Authority (VIHA) Well Nos 1 and 2 was reported to be 56 and 60 feet, respectively. VIHA well Nos. 1 and 2 are located approximately 175 feet west of the Laga Building. Ref. Nos. 1,9 02-8902-44-PA Rev. No. 0 5. What is the permeability value of the least permeable continuous intervening stratum between the ground surface and the aquifer of concern? There are no continuous intervening strata between the ground surface and the bedrock aquifer. Soils are generally thin in the area around the site. The water-bearing formations in the Turpentine Run Basin are composed primarily of fractured and jointed volcanic rocks. The range of hydraulic conductivities associated with these formations is 10'3 to 105 cm/sec. Ref. Nos. 10, 11, 16 6. What is the net precipitation for the area? Net precipitation is usually calculated by subtracting mean annual lake evaporation (a surrogate measure for evapotranspiration) from normal annual total precipitation. Mean annual lake evaporation was not available for St. Thomas; however, evapotranspiration data were available. These data indicate that 95.8 percent of the incident precipitation on St. Thomas is lost through evapotranspiration. The normal annual total precipitation for St. Thomas is 43.74 inches, but because of orographic effects on the Island, normal annual total precipitation can range from 35 inches to 50 inches over short distances. In the Turpentine Run Basin, normal annual precipitation is 40 inches. Calculations for net precipitation are provided below: 40 inches precipitation x 95.8 percent lost to evapotranspiration = 38.32 inches lost to evapotranspiration 40 inches precipitation - 38.32 inches lost to evapotranspiration = 1.68 inches net precipitation. Ref. Nos. 3, 5, 12, 13 7. Identify uses of groundwater within 3 miles of the site (i.e., private drinking source, municipal source, commercial, industrial, irrigation, unusable). Groundwater within 3 miles of the site is used as a source of private and municipal drinking water, and for commercial purposes. There are at least 41 wells within 2 miles of the site. Thirty-five of these wells are within 1 mile of the site. Ref. Nos. 6, 9 8. What is the distance to and depth of the nearest well that is currently used for drinking or irrigation purposes? Distance 175 feet______ Depth 150 feet_________ The nearest well is the VIHA well No. 2, which is located approximately 175 feet west of the Laga building. This well is believed to be used for drinking. A nearby well, VIHA No. 1, was ordered closed because of contamination with volatile organic compounds. VIHA well No. 2 is not listed as being closed due to contamination, and its designated use is for domestic purposes. Ref. Nos. 6,9 9. Identify the population served by the aquifer of concern within a 3-mile radius of the site. It is difficult to estimate the population served by groundwater on St. Thomas as there are few records available on groundwater withdrawal, sale, and transport. The locations of some wells in St. Thomas are unknown, and there are reports of illegal drilling on the island. It is estimated that there are 500 to 600 private wells on St. Thomas. Most of these are used for nondrinking domestic uses such as washing and flushing, although some may be used for drinking. There are a number of wells that are used for commercial purposes. Water from these wells is trucked to private houses and pumped into cisterns to augment the rainwater collected from roofs. Groundwater is also bottled and sold in supermarket* 02-8902-44-PA Rev. No. 0 There are at least 41 wells in the Turpentine Run Basin. Recently, 16 of these wells have been ordered closed because they were found to be contaminated with volatile organic compounds. One of these wells was a major supplier of water to the eastern end of the island. Estimates of the population using groundwater as a source of drinking water range from none to approximately 11,000-the population of the Turpentine Run Basin which is not served by water from a desalinization plant. The actual population served by groundwater is probably less than 11,000, as desalinated water and water from wells outside the 3-mile radius is trucked into the area. Ref. Nos.9, 13, 15, 18, 19 SURFACE WATER ROUTE 10. Describe the likelihood of a release of contaminant(s) to surface water as follows: observed, alleged, potential, or none. Identify the contaminant(s) detected or suspected, and provide a rationale for attributing the contaminants to the facility. A potential exists for contaminants to be released to surface water. The location of the drums is at the top of a steep hill, and at the base of the hill is a tributary to Turpentine Run -- an intermittent stream which drains the Tutu area and discharges to the Caribbean Sea. The drums have not been sampled, and there is no historical information that indicates what their contents are. The DPNR indicated that the Laga Building was a former textile processing facility which used sol vents in its processes. Ref. Nos. 1,2 11. Identify and locate the nearest downslope surface water. If possible, include a description of possible surface drainage patterns from the site. The nearest downslope surface water is the Mangrove Lagoon which is hydraulically connected to the Caribbean Sea. Turpentine Run is an intermittent stream that drains the Turpentine Run Basin. The distance from the site to the nearest surface water, along the course of Turpentine Run, is 2.4 miles. It should be noted that because of the steeply sloping nature of the topography on St. Thomas (35-percent slopes are not uncommon), there are no natural perennial streams on the island. On St. Thomas orographic effects produce frequent, brief rainstorms. Runoff from these rainstorms can be significant, and therefore, short-term flow rates of the intermittent streams can be high. Ref. Nos. 2, 4, 5 12. What is the facility slope in percent? (Facility slope is measured from the highest point of deposited hazardous waste to the most downhill point of the waste area or to where contamination is detected.) The drum area is relatively flat with a slight slope toward the north and east. Near the margin of the drum area there is a steep slope to the northeast. Facility slope is estimated to be between 0 and 3 percent. Ref. Nos. 1,2 13. What is the slope of the intervening terrain in percent? (Intervening terrain slope is measured from the most downhill point of the waste area to the probable point of entry to surface water.) The slope of the intervening terrain is as follows: • Elevation of waste area - 240 ft • Elevation at point of entry-0 ft • Path length - 12,700ft 02-8902-44-PA Rev. No 0 240 ft - 0 ft x 100 = 1.9% slope 12,700ft Ref. Nos. 1,2 14. What is the 1-year 24-hour rainfall? One-year 24-hour rainfall data were not available for the U.S. Virgin Islands. However, it is known that rains exceeding 1 inch in 24 hours occur six or seven times a year on St. Thomas. Two-year 48-hour rainfalls range from 4 to 15 inches. It has also been reported that it is not uncommon for 24-hour rainfalls to be 2 to 3 inches. Ref. Nos. 4, 6 15. What is the distance to the nearest downslope surface water? Measure the distance along a course that runoff can be expected to follow. The nearest downslope surface water is the Mangrove Lagoon, which is hydraulically connected to the Caribbean Sea. The distance from the site to the above surface water is 2.4 miles. Ref. No. 2 16. Identify uses of surface waters within 3 miles downstream of the site (i.e., drinking, irrigation, recreation, commercial, industrial, not used). Surface water within 3 miles downstream of the site is used for recreation including swimming, fishing, and boating. The DPNR has designated the area of the Mangrove Lagoon for preservation. Ref. Nos. 2, 14 17. Describe any wetlands, greater than 5 acres in area, within 2 miles downstream of the site. Include whether it is a freshwater or coastal wetland. There are no wetlands greater than 5 acres within 2 miles downstream of the site. However, there is a coastal mangrove wetland approximately 2.4 miles downstream. The Mangrove Swamp is designated as a preservation area in the Coastal Zone Management Program of the DPNR. Ref. Nos. 2, 14 18. Describe any critical habitats of federally listed endangered species within 2 miles of the site along the migration path. There are no known critical habitats of federally endangered species within 2 miles of the site. The Virgin Islands Tree Boa (epicrates monensis qranti) is an endangered species in the U.S. Virgin Islands; however, no critical habitat has been identified for this species. Ref. No. 7 19. What is the distance to the nearest sensitive environment along or contiguous to the migration path (if any exist within 2 miles)? There are no sensitive environments within 2 miles of the site that lie along or contiguous to the migration pathway. Ref. Nos. 2,7, 14 02-8902-44-PA Rev. No. 0 20. Identify the population served or acres of food crops irrigated by surface water intakes within 3 miles downstream of the site and the distance to the intake(s). There is no population served and there are no food crops irrigated by surface water intakes within 3 miles downstream of the site. The nearest surface water is saline. There is a desalinization plant which uses seawater to supply drinking water, but the intake is greater than 3 miles from the site. Ref. Nos. 2, 13 21. What is the state water quality classification of the water body of concern? No water quality classification is known to exist for the Mangrove Lagoon or the Caribbean Sea, although the mangrove swamp surrounding the lagoon is designated as a preservation area by the DPNR. Ref. Nos. 14 22. Describe any apparent biota contamination that is attributable to the site. No apparent biota contamiantion was observed during the on-site reconnaissance conducted by NUS Corp. Region 2 FIT on February 15, 1989. Ref. No. 1 AIR ROUTE 23. Describe the likelihood of a release of contaminant(s) to the air as follows: observed, alleged, potential, none. Identify the contaminant(s) detected or suspected, and provide a rationale for attributing the contaminant(s) to the facility. A slight potential exists for release of contaminants to the air. If corroded and uncontained drums rupture, the potential exists for a release to the atmosphere. The type of wastes in the drums is unknown; however, prior to ownership by the Department of Education, the building housed a textile processing facility that is reported to have used solvents. No readings above background were detected on the OVA flame ionization detector or the HNu photoionization detector during the on-site reconnaissance of the drum area conducted by NUS Region 2 FIT on February 15, 1989. Ref. No. 1 24. What is the population within a 4-mile radius of the site? Based on the 1980 census, the population within 4 miles of the site is approximately 36,000. Ref. No. 17 FIRE AND EXPLOSION 25. Describe the potential for a fire or explosion to occur with respect to the hazardous substance(s) known or suspected to be present on site. Identify the hazardous substance(s) and the method of storage or containment associated with each. A small potential exists for fire or explosion to occur at the site. Solvents were reportedly used in the textile processing that took place in the Laga Building. If these solvents are contained in the drums, there is a potential for fire or explosion. Drums on the site were in poor condition, and there were no containment structures around the drums. Ref. No. 1 26. What is the population within a 2-mile radius of the hazardous substance(s) at the facility? Based on 1980 census data, the population within 2 miles of the site is approximately 19,000. Ref. No. 17 02-8902-44-PA Rev. No. 0 DIRECT CONTACT/ON-SITE EXPOSURE 27. Describe the potential for direct contact with hazardous substance(s) stored in any of the waste units on site or deposited in on-site soils. Identify the hazardous substance(s) and the accessibility of the waste unit. The potential exists for direct contact with hazardous substances at the facility. The drums are uncontained and were deposited in an uncontrolled manner. It is not known whether the drums contain hazardous substances; however, solvents have been associated with this site in the past. The waste is not surrounded by a fence, and children were observed near the drum area. There are residences 230 feet east and downhill from the drum area. Ref. Nos. 1,2 28. How many residents live on a property whose boundaries encompass any part of an area contaminated by the site? It is not known whether any area has been contaminated by the site. 29. What is the population within a 1-mile radius of the site? Based on 1980 census data, the population within 1 mile of the site is approximately 11,000. Ref. No. 17 02-8902-44-PA Rev. No. 0 PART IV: SITE SUMMARY AND RECOMMENDATIONS The Laga Building Site is located in the Tutu area of St. Thomas, U.S. Virgin Islands. The Laga Building was formerly the site of a textile manufacturing facility and is currently occupied by the Virgin Islands Board of Education. The area within approximately 1 mile of the site is densely populated, and includes some commercial properties. There are large housing developments north, northwest, and southeast of the site. The nearest residence is 320 feet east of the site. Beyond 1 mile, there are scattered smaller villages and towns. The densely populated and highly commercial town of Charlotte Amalie, which is the capital of St. Thomas, is located 2.5 miles west of the site. On February 15, 1988, NUS Corp. Region 2 FIT conducted an on-site reconnaissance of the Laga Building Site. Twenty-two 55-gallon drums were found behind the building. The drums were deposited in an uncontrolled manner, and most of them were in poor condition. Some of the drums were rusted, some were perforated, some were deposited on their sides, some were empty, and at least one was full. Vegetation has grown around most of the drums, and a few were nearly completely overgrown. There were no discernible labels on the drums. No stains were noted near the drums, and no readings above background were detected on the OVA flame ionization detector or the HNu photoionization detector. There are no containment structures surrounding the drums, and the DPNR indicated that solvents were used by the textile processing facility that previously occupied the building. The above conditions indicate that there is a potential for contaminants to be released to the environment from the drum area behind the Laga Building Site. A tributary of Turpentine Run is located downhill and approximately 250 feet east of the drum area. Turpentine Run is an intermittent stream that drains the Turpentine Run Basin and discharges to the Mangrove Lagoon, which is hydraulically connected to the Caribbean Sea. If hazardous substances are released from the drums, the potential exists for them to be transported to the Mangrove Lagoon via Turpentine Run. The DPNR has designated the mangrove wetlands for preservation. There is also concern that hazardous substances that may be in the drums will be released to groundwater. The site is atop the Turpentine Run Basin Aquifer, which is the most productive aquifer on St. Thomas. There are numerous wells in the Turpentine Run Basin Aquifer, and collectively they are permitted to draw up to 1 million gallons per day from the aquifer. Some of these wells draw water for drinking purposes. Currently, the water main from a public water supply desalinization plant does not extend to the Tutu area. There is also a potential for fire and/or explosion, direct contact, and air contamination from the drums. The drums may contain solvents that may be flammable or explosive. Direct contact is 02-8902-44-PA Rev. No. 0 possible if hazardous substances are present in the drums. The nearest residence is 235 feet east of the site, and children have been observed walking near the drums. The potential for air contamination exists if volatile compounds are released from the drums. The previous owners of the Laga Building have been identified as one of nine potentially responsible parties in the contamination of groundwater in the Tutu area. In July and August of 1987, ERA confirmed by sampling that volatile organic compounds were present in a number of wells in the Tutu area. DPNR has issued orders to close 16 wells in the area. One of the wells was a major source of commercially provided potable water for the eastern end of the island. Removal action activities in the Tutu area included sampling of wells and cisterns, removal of contaminated water from cisterns, cleaning of cisterns, and supplying clean water on a regular basis to affected residents The Laga Building Site is given a.MEDIUM PRIORITY for further action for the following reasons: • Waste containment is poor as evidenced by perforated and corroding drums. • Groundwater in the vicinity of the site is used for domestic purposes, and the water main from the desalinization plant does not currently extend to the Tutu area. • The potential exists for runoff from the site to reach the Mangrove Lagoon via Turpentine Run. • The waste area is accessible, and there are homes 230 feet east and downhill of the drum area. Further efforts should focus on determining whether there are hazardous substances in the drums. Efforts should also be directed toward determining whether any hazardous substances have been released to the environment. Drum sampling and soil sampling in the vicinity of the drums and soil sampling in the drainage pathway to Turpentine Run are recommended. Sampling of wells in the vicinity of the site is also recommended. It should be noted that a number of the wells are contaminated with volatile organic compounds; therefore, judgement should be used to select appropriate wells for sampling. ATTACHMENT A MAPS AND PHOTOS 02-8902-44-PA Rev. No. 0 LAGA BUILDING ST. THOMAS, U.S. VIRGIN ISLANDS CONTENTS Figure 1: Site Location Map Figure 2: Site Map Exhibit A: Photograph Log 02-8902-44-PA Rev No. 0 INTERMITTENT STREAM HOUSES SITE MAP LAGA BUILDING. ST. THOMAS, U.S. VIRGIN ISLANDS NOT TO SCALE rUT 002 0(">'7::::, FIGURE 2 CXDRFORATTON 02-8902-44-PA Rev. No. 0 *> J- "n *'——^ ^Ci^-^''"^ ^—_ " , ' * , • _ • / «•* J'///1/f/^' *_X,/ i ""^^vVv"^" "-J^->*r 0 v—*'.jE^r * ".k'T • Vs—*" "-r^!.- K - V - s ^ r - ^r^r-: 1~_^'*''--.'''.^^(W*X( ^»\^^^V-..-.-:K. -Vr .> -^gp " MANg^jB^Y^^r ^;: <^^|S%i:^/|^^^ VIRGIN ISLANDS "^ -.iv'.-^-^K / • "\ .. • . ' ^T''"'. '<f ^I/ • •^^^K'/*^''' -''^L''''. '/§5'''" ' > '^X^—'^^-'~ ' '' (QUAD) EASTERN ST. THOMAS, V.I. SITE LOCATION MAP LAGA BUILDING ST. THOMAS, U.S. VIRGIN ISLANDS SCALE: r- 2000' MUS CORPORATmM 02-8902-44-PA Rev. No. 0 LAGA BUILDING ST. THOMAS, U.S. VIRGIN ISLANDS FEBRUARY 15, 1989 — PHOTOGRAPH INDEX ALL PHOTOGRAPHS TAKEN BY DIANE TRUBE. Photo Number Description Time R3-P17 Drums behind Laga building. 1525 R3-P18 Drums behind Laga building. 1525 R3-P19 Drums behind Laga building. 1525 TUT 00 i IMUS CORFORAnON 02-8902-44-PA Rev. No. 0 LA6A BUILDING ST. THOMAS, U.S. VIRGIN ISLANDS R3-P17 February 15, 1989 Drums behind Laga building. 1525 IMUS CORPORATION 02-8902-44-PA Rev. No. 0 LAGA BUILDING ST. THOMAS, U.S. VIRGIN ISLANDS R3-P18 February 15, 1989 Drums behind Laga building. 1525 IMUS 02-8902-44-PA Rev. No. 0 LAGA BUILDING ST. THOMAS, U.S. VIRGIN ISLANDS '<." ^ .•&%&£$& R3-P19 February 15, 1989 Drums behind Laga building. 1525 ATTACHMENT B REFERENCES 02-8902-44-PA Rev. No. 0 REFERENCES 1. Field Notebook No. 0398, U.S. Virgin Islands Drum Reconnaissance, TDD No. 02-8902-29, NUS Corp. Region 2 FIT, Edison, New Jersey, February 14 to 17, 1989. 2. U.S. Department of the Interior, Geological Survey Topographic Maps, 7.5 minute series, "Central St. Thomas, Virgin Islands and Eastern St. Thomas, Virgin Islands Quadrangles" 1955, revised 1982. 3. Gomez-Gomez, F. and J.E. Heisel. Summary Appraisals of the Nation's Groundwater Resources-Caribbean Region. Geological Survey Professional Paper 813-4, 1980. 4. Stone, R.G. Scientific Survey of Porto Rico and the Virgin Islands, Volume XIX - Part 1, Meteorology of the Virgin Islands. 1942. 5. Climate of Puerto Rico and Virgin Islands, Climatography of the United States No. 60, June 1982. 6. Tutu Well Site Potable Water Alternatives Report, Anna's Retreat, St. Thomas, U.S. Virgin Islands. Prepared for U.S. EPA Region 2 By Region 2 Technical Assistance Team, Weston/SPER Division, December 1989. 7. Fish and Wildlife Service List of Endangered and Theatened Wildlife and Plants. 50 CFR 17.11 and 17.12. February 1985. 8. Telecon Note: Conversation between Nancy Schlater, EPA, and Diane Trube, NUS Re: Sole source aquifer in VI, March 3,1989. 9. Graves, R.P. and R. Gonzalez. Potentiometric surface of the Turpentine Run Basin Aquifer in the Tutu Area, Eastern St. Thomas, U.S. Virgin Islands, September 11, 1987. U.S. Geological Survey Water Resource Investigations Report 88-4131, 1988. 10. Uncontrolled hazardous waste site ranking system, A user's manual, 40 CFR, Part 300, Appendix A, 1986. 11. Donnelly, T.W., Geology of St. Thomas and St. John, U.S. Virgin Islands, In Caribbean Geological Investigations, Geological Society of America, Memoir 98. ed. H. H. Hess, 1966. 12. Climatological Data Annual Summary, Puerto Rico and Virgin Islands. National Oceanic and Atmospheric Administration, 1987. 13. Torres-Sierra, H. and R. Dacosta, Estimated Water Use in St. Thomas, U.S. Virgin Islands, July 1983 to June 1984. Caribbean Research Institute, Technical Report No. 21. 14. U.S. Virgin Islands Department of Planning and Natural Resources, Coastal Zone Management Program, zoning districts and coastal land and water use plan map. 15. Memo to Stephen D. Luftig, EPA, from Carlos O'Neill, EPA. Authorization of CERCLA Removal Action Monies for the Tutu Well Site. January 6, 1988. 16. Jordan, D.G. and O.J. Cosner, A Survey of the Water Resources of St. Thomas, Virgin Islands, U.S. Geological Survey Open File Report, 1973. 17. Water Management Plan for the Public Water System, Prepared for the Government of the Virgin Islands by CH2M HILL July 1983 Rev. No. 0 REFERENCES (CONT'D) 18. Telecon Note: Conversation between Fernando Gomez, USGS and Rich Feinberg, NUS Corp., on 3/11/89 at 1045 hours. RE: Hydrology and groundwater use in St. Thomas. 19. Telecon Note: Conversation between D. Goetz of Polycaribe and D. Trube, NUS Corp., on 3/14/89 at 1430 hours. RE: Wells and water use on St. Thomas. 20. Telecon Note: Conversation between L. Reed, DPNR, and D. Trube, NUS Corp., on 3/3/89 at 1640 hours. RE: Permits for site on St. Thomas. REFERENCE NO. 1 NUS CORPORATION II I 0398 OL - V ~ C / C < -Z? o,\ f ^ r-- of; v---V r- Yacht- r ~1 1 fQ. 'O miic \cxw\ - O M V i ""Brecon ^ *~V<-<,' TCf A/ O?CO ^T> (O W. ) w T/9T" .s. o-r ^ f o ex. ^ J__c.c _ _k>jwwnct_ o* . r_^ J. _^*-'*Xx- ^ €. <3cH-Cu<Jt> -73 i rT C xt-v ^.-r&.a re ' & "ror /pcj.._-Vo._s>L<) h' .=.'.' 1 8 _ TCf i<n, M-ii <..& ^ UJ<? o <->•»" T>r- 4, r . J-. He. —— . — .^po p- as. -_t i.n r ' / (o j Q-'V _ .r .c M\ 4nD.. m, re h^rnog rT^c - llT ( R-V $% LL \ -4 ^ i° V T -^sSLs oQ ~Ci •Sdvx iP^^n^ °f W^^ i-»^ ^ -^ .S 1- ;'-.^' , :-»3 &-;;;..?,' *^?: S*•X'-SK-xa TLi OO'i ;')0'- ^/^W .^ -v,'.•:•.• '/* REFERENCE NO. 2 ^ . :^"n"": \ /; •<g-T-'Va*gtt rn^?.WN .. ^^-^' SwiiN^&^^^M1 1—' ^ ••". v./rv. ^fV - --ul: - "Y VK VIRGIN ISLANDS "T -.ItV'-?^ / . \v. •, -'' 'jfj^--'. -^ ''- ' (QUAD) EASTERN ST. THOMAS, V.I. LAGA BUILDING ST. THOMAS, U.S. VIRGIN ISLANDS SCALE: V- 2000' REFERENCE NO. 3 Summary Appraisals of the Nation's Ground-Water Resources — Caribbean Region By FERNANDO GOMEZ-GOMEZ and JAMES E. HEISEL G E O L O G I C A L S U R V E Y P R O F E S S I O N A L P A P E R 8 1 3 - U U N I T E D STATES G O V E R N M E N T P R I N T I N G OFFICE, W ASH I N GTO N : 1 980 U20 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES TABLE 4. - Water budget, in cubic hectometers per year fkml/yr) and percent, for Puerto Rico Iby West coast to RioGrmndc >te Arecibo hm*/yr Percent North Coast Province Rio Grande de Arecibo to Rio de La Plau hm'/yr Percent Puerto Rico South Province RiodeU Plata to Rio Espiritu Santo hmVvr Percent PatiUas to Ponce hmVyr Percent Tallaboa to Guanica hmVyr Percent Lajai VaJley hm'/yr Percent WestCout province hm'/vr Percent Input Precipitation Stream How Diversions I.280 "ic.4 1.030 U6 Ii70 M 2 jao 46.8 410 :>0.6 so a. a 60 175 25.5 745 100 4 4 33 , 72.8 3.2 24.0 MO a.a 880 71.0 Output £vapolraspiration Stream outflow <iround-water loss to wetlands or **a (miund-waler withdrawals': Total Industry [rrwauon Public supply 15 7 304 34.8 1360 .Mf.K H6 ;j.7 60 2.6 26 (00 ^3.8 »20 73.0 20 1 6 20 1.6 5 15 __ 430 53.1 ISO 23.5 20 2.5 17U 210 143 I-III 60 100 15 60 37 2 2S.5 42.6 6.4 2S.S 12U 11 6.3 .1 873 X.O 4 6 I .'70 21.8 a20 74.2 40 3.2 10 8 10 1 All ground wal*r withdrawn was asHumed to b* for cunsumptiun strut it is n<it available fur i>ther uses. 1000 •00 < (00 a. 400 £ 200 o Public Supply (Puerto Rico Aqueduct and Sewer Authority) (00 400 200 19*0 I9<9 1970 1979 I9M 1919 1990 1999 2000 YEARS 29 20 5 » w >- 10 £ s o LISHT IIMWSTHY ,--" ' DOMESTIC AND COMMERCIAL TOTAL WtTHOHIWALS (Eiel««tl 1969 1970 1979 I9«0 19*9 1990 1999 2000 FH;I KK 1".-Water-use estimates. A. For Puerto Ricu: public-supply data provided hy the Puerto Rico Aqueduct and Sewer Authority (modified (r«m Morris. 1976). B. For the U.S. Virgin Islands. CARIBBEAN REGION province) and its offshore itiands (Vieques. CuMrra, and Mono. Islands) and for the U.S. Virgin Islands. 1975 U21 Ewt Coast pruvimv hmj/vr Prro-nt Purru. Kirti-Ciinlini inu*rx>r Purrui Kicn hnv*/vr Pf rw til hmj(\ r Perrrnl hm Uff I'.S. Virgin l.iluftii- Purrl»> KK-U s d|Tsh<>rt islarmr- Vivqw> Cuk-bra Mmi;< S(. Lmi* Si Th<nn;i> * Si J<-fin J'>r Perrt-nl hmj/>r Prrrrnl hm'i\i Ht-rtt-nl hm v i Ptrn-nl hmf-yr p^nvnl hmj/\r Ht- m nl Input — Continued 100 IJ.SiJO 278 580 12 Z Output — Continued ^ — 31 (J 6.512 5SS lu.!5ti M.2 110 ill. 7 24.11 S5 S 39.'. 87 K 2".". S3. 2 SI (fiiiiJ .".4 SH.2 64 4 4.342 3S.S 5.U46 31. » li Ti.O 7 2.K I) 0 o 3.1. 2.1. 27 J 7 3.3 __ __ 2W) l.h 33 2.7 .3 12 3..'. 12.2 a.fi 2..> 1.2 1J .1. 1.1 1.3 16 .2 35S 2.3 .7 .6 .04 .2 » (I l . f i .7 .2 2 __ . II lgg .... .... __.. .... .... .... .... _... .... .... .... .... PROBLEMS AFFECTING USE OF WATER RESOURCES MANAGEMENT—PUERTO RICO By adoption of Law No. 23 of January 1973, the Puer- to Rico Department of Natural Resources (DNR) was charged with the responsibility for implementation of the operational phase of the public environmental policy of Puerto Rico. Law No. 23 also provides for centraliza- tion of operational functions and implementation of regulations that had previously been dispersed throughout many governmental agencies. In addition, the new Water Law, No. 136 of June 3, 1976, assigned to the Secretary of DNR the responsibility to plan and regulate the use of and to improve, conserve, and develop the waters of Puerto Rico. In acknowledgment of the need for a centralized information center, the new water law also stipulates that the Secretary be assisted by a staff that has representatives from the Planning Board, the Puerto Rico Industrial Development Com- pany (PRIDCO), the Environmental Quality Board (EQB), the Puerto Rfco Aqueduct and Sewer Authority (PRASA), the Puerto Rico Water Resources Authority (PRWRA), the Department of Agriculture (DOA), the Department of Health (DOH), the Department of Trans- portation and Public Works, and the University of Puer- to Rico. Although numerous government agencies (State and Federal) and institutions are involved in the use, plan- ning, management, and investigation of the water resources, the DNR, EQB, U.S. Environmental Protec- tion Agency (EPA), PRWRA, PRASA, Puerto Rico Sugar Corporation, and heavy water-use industries established by PRIDCO exert the greatest influence over the future of this resource. The responsibilities these agencies and public corporations have with respect to water resources are listed as follows: DNR. The functions of this Puerto Rican agency were established by Laws No. 23 and No. 136, previously stated. EQB. This is the Puerto Rico policy-making and regulatory agency responsible for the enhancement and protection of water quality; it is invested with quasijudicial powers to enforce its regulations. For purposes of the Federal Water Pollution Control program (Public Law 92-500) the Board is designated the State water-pollution control agen- cy. EPA. This is the Federal agency charged with ad- ministration of Public Law 92-500 aimed at restor- ing and maintaining the chemical, physical, and biological integrity of the Nation's waters. Among the programs the agency administers are establish- ment of effluent limitations, administration of the National Pollutant Discharge Elimination System, and management and planning for public water- supply treatment-works construction. PRWRA. The authority produces and distributes elec- trical energy and administers and operates the irri- gation systems supported by releases from reser- voirs and the hydroelectric power-generation net- work on the south coast and in northwestern Puerto Rico. PRASA. The authority is charged with development, construction, operation, and maintenance of water and sewer systems and providing adequate water TVJ U22 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES and sewer services and any other related services and facilities. Puerto Rico Sugar Corporation. A public corporation created by legislative action in 1973 to consolidate the operations of the sugar industry (cultivation and refining). The corporation manages all the 11 mills on the island, 7 of which are government owned. The corporation also manages cane cultivation on 29,600 ha of both government-owned and leased land. PRIDCO. This is the principal Puerto Rico governmen- tal agency charged with the responsibility for the economic development of Puerto Rico. With its associated public corporation, the Government Development Bank, it devises methods to accelerate economic development, especially through industrial promotion and tourism. This agency must submit to ONR and EQB an environmental-impact statement for each industrial project it proposes to develop. The agency also cooperates closely with the Plan- ning Board in preparing its plans and programs. The new centralized form of management stipulated in Law No. 136 of June 3, 1976, is intended to improve in- stitutional structures to aid optimum water-resources development. MANAGEMENT—U.S. VIRGIN ISLANDS In the U.S. Virgin Islands, the Department of Conser- vation and Cultural Affairs is charged with the ad- ministration and enforcement of all laws relating to water resources and water pollution, under Title 3, Chapter 22, of the Virgin Islands Code as of June 4, 1968. Other agencies involved with the management of the water resources are the Public Works Department, the Water and Power Authority, and the Virgin Islands Planning Office. The functions of each of these are outlined as follows: Public Works Department. Under Title 30, Section 51, of the Virgin Islands Code, the Commissioner of Public Works is designated to supervise and control the construction, repair, maintenance, operation, and administration of the potable-water systems. The potable-water system was defined as "all fresh water stored or collected by the government, whether in catchments, dams, wells, or reservoirs, for public distribution." Virgin Islands Water and Power Authority (WAPA). This authority was established in 1964 under Virgin Islands Code, Section 103, Title 30, for production and distribution of electrical energy and provision of potable water from its water-distillation systems. In the enabling legislation is a provision, 104e, for the transfer of the water-supply functions of the Public Works Department to WAPA at a date to be deter- mined by law. The transfer of functions has not been acted upon by the legislature, and WAPA sells the distilled water to the Public Works Department. U.S. Virgin Islands Planning Office. This office is designated as the government agency in charge of water-management planning; the agency is also en- titled to appropriate funds received under the title 3 program. The Public Works Department is by far the major ground-water user. Agriculture is almost nonexistent in the islands, and industries that depend heavily on water obtain their water from self-owned desalination plants. For these reasons, a lack of coordination among water users is not a major problem affecting ground-water resources in the Virgin Islands. WATER RIGHTS Water rights and laws regulating water use have been established by society to assure the minimum re- quirements of individuals and communities, to promote the beneficial development of water resources, and to respect legal access to water sources. These laws, which have been implemented to reduce friction between users, ironically become constraints if they are not adapted to the needs of a modern technological society. On June 3, 1976, the Commonwealth Legislature approved the Law of Waters (Law No. 136) for Puerto Rico, which declared all waters within Puerto Rico the patrimony and wealth of the People of Puerto Rico; en- dowed the Secretary of Natural Resources with the power to plan and regulate the use, conservation, and development of the water resources and to implement the public policy and regulations related to the waters of Puerto Rico; and annulled two provisions of the Civil Code and the Law of Waters of March 12, 1903. The 1903 water law was essentially that which had been in effect in Spain since 1879 and had been extended over Puerto Rico by order of the King in 1886. Article 16 of Law No. 136 recognized acquired rights that make beneficial and reasonable use of water and were in ex- istence prior to June 3, 1976, including those conces- sions from the Spanish Crown. Acquired rights under the old Spanish law were ob- tained according to the prior-appropriation doctrine. For example, "any landowner may utilize the pluvial and other waters flowing intermittently in public channels or along roads" (Art. 6, 176, 177); "after use for one year and a day, he establishes a temporary right that is superior to that of any subsequent user," on the principle that first in time is first in right (Art. 7); "after water has been used without interruption for 20 years, the appro- priator acquires the right to continue the use indefinite- CARIBBEAN REGION U23 ly" (Art. 8). Similarly, as to "artesian wells, tunnels, or galleries," (major ground-water developments as oppos- ed to "ordinary wells," which are defined (Art. 20) as those for which no other motive power than man is employed for raising the waters), the right of the person discovering and bringing the water to the surface is recognized "in perpetuity," as long as such development does not interfere with preexisting rights to public or private waters (Art. 23). These rights (surface- or ground-water appropriation) were also recognized for all individuals who had enjoyed the use of public waters for a period of 20 years (prior to 1886) even though no proper authorization had been obtained. The order of preference in utilization stipulated by the previous law (Art. 160 of the Spanish Water Law) ex- pressed the needs of the past century. First priority was given to water supply of towns, followed by water sup- ply of railroads, irrigation, navigational canals, mills and other factories, ferry boats and floating bridges, and fishponds. The economic importance of water-using in- dustries was not foreseen, and a low preference as to water concessions was stipulated. Duration of the con- cessions was limited to 99 years of town supplies (Art. 170) and all other uses but was "in perpetuity" for irriga- tion (Art. 188) and fishponds and also for industry, as long as effluents were not harmful to health or vegeta- tion (Art. 220). As of 1909 there were approximately 250 concessions in Puerto Rico that were originally granted by the Spanish Crown (Report of the Governor of Puerto Rico, 1909). The majority of these grants were given to lan- downers in the South Coast province for the irrigation of approximately 21,000 ha. The surface-water conces- sions included rights to flood-waters, spring and winter waters, or a definite daily flow. An updated inventory of vested owners, diversion amounts, and land under irrigation is necessary to determine the degree to which these rights could affect a water-use and distribution plan. In the Virgin Islands, all waters are in public owner- ship and are subject to appropriation for beneficial use as stipulated in Chapter 5, Title 12, of the Virgin Islands Code. Under this policy, vested rights are recognized prior to other appropriation. Vested rights may be nullified by the government of the Virgin Islands (Com- missioner of Conservation and Cultural Affairs) when it is determined that the exercise of such rights would im- peril health or welfare by endangering, impairing, or destroying available sources of water. Nevertheless, the occurrence of such circumstances is very remote, as most private installations are for domestic use and withdraw less than 2 m3/d. An exception could be those individuals and companies that sell water obtained from wells. Under Section 153 of Title 12, appropriation per- mits are not required if pumpage is less than 2 m3/d for beneficial use. Under Chapter 3, Title 12, of the Virgin Islands Code, trees and other vegetation adjacent to watercourses are protected by law. This regulation protects the esthetic values of stream channels but results in a significant loss of ground water to evapotranspiration by the deep- rooted vegetation. A modification of this law would be necessary in order to exclude from such provision those watercourses that are used for public supplies or are in hydraulic connection with aquifers tapped for supply. PRACTICES DETRIMENTAL TO GROUND-WATER QUALITY LAND USE Land use may affect recharge to an aquifer and the quality of its water. Although there has been no exten- sive evaluation of the effects of various land uses on aquifers in the Caribbean Region, data from scattered sources indicate that this could be a major problem in the near future. Urbanization has taken over large portions of the recharge areas of aquifers in metropolitan San Juan, Ponce, and Mayaguez in Puerto Rico and throughout the Virgin Islands of St. Croix and St. Thomas. Unless ar- tificial recharge is provided or withdrawals are reduced to compensate for the loss of recharge, the seawater- freshwater interface will move inland in most of these areas. Aquifers in the Caribbean Region are threatened by pollution from domestic, municipal, and industrial sources. The most widespread source of pollution is pro- bably sewage from cesspools, leaking sewage lines, and overloaded or improperly operating sewage plants. In Puerto Rico about 37 percent of the population is served by sewers, and in the U.S. Virgin Islands approximately 77 percent is served. In generalt_theonly areas served by sewers are those within the urban limits nf t.pyvns. Ihdustriafwastes have been discharged to aquifers through sinkholes and disposal wells or have entered aquifers from accidental spillage (D.G. Jordan, written commun., 1969; R.C. Vorhis, written commun., 1972). Of the 15 disposal wells known to exist in 1972, only 2 could be designated as deep injection wells, and the others could better be designated waste-disposal holes. All the known disposal holes were between 24 and 213 m deep. Wastes disposed in sinkholes and disposal holes in- clude sewage, oil, neutralized acid, organic compounds, dyes, pickling liquors, pineapple-cannery wastes, and brewery wastes. Jordan (written commun., 1969) estimated there were at least 40 such disposal holes in Puerto Rico in 1969. It has also been observed that unproductive wells are either abandoned without plugging or are not thor- U24 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES oughly sealed. A3 a result many are used as receptacles for wastes. The effects on water quality and the extent of damage this has caused in the Caribbean Region have not been assessed. In the Lajas Valley, Vazquez and Ortiz-Velez (1967) observed that a downward hydraulic gradient existed at various abandoned irrigation wells. These wells probably are serving as hydraulic connec- tors between perched water tables and the underlying regional water table. The effect of these "hydraulic con- nectors" on water quality is unknown. Disposal of refuse in landfills poses another threat to aquifers in Puerto Rico. Most landfills were estalished after 1972 (fig. 18), and although migration of leachates may be slow at some sites, with time these will inevi- tably affect to some degree the local ground-water sources. In the U.S. Virgin Islands, landfills have been established near the coast on St Croix and St. Thomas, and contamination of freshwater sources is not a threat. The landfill on St John, however, is located in the in- terior Guinea Gut Basin, where potential for ground- water development exists. IRRIGATION PRACTICES Irrigation of crops occurs primarily in southern Puer- to Rico. The basic means of distributing water within cultivated lands is by furrows, although overhead sprinklers are used at some farms in the early months of sugarcane cultivation. Giusti (1971) estimated that ap- proximately 30 percent of the applied water in the South Coast province (Coamo area) was recharged to the aquifer. Bennett (1976) indicated that the ground-water reservoir in the South Coast province is 'Vertically oriented," in that local recharge and discharge tend to be high in any given locality relative to lateral ground- water flow. In areas where irrigation water is derived from wells, recycling of the irrigation water will result in an increase in the dissolved-solids concentration of the ground water. erar 30- \rja- - mxr PUERTO RICO I_________I____ EXPLANATION Munfcipelfolttwam d to 85*15' T isis-ar CULEBRA 1815' - 6*00' —T 64*45' ST. THOMAS /r <« T^/^^-i / ST. JOHN i ^) 64-45' VIEQUES ST. CROIX Fwinz 18.- Sotid-wMte dispowl ntee in the Caribbean Region. CARIBBEAN REGION U25 During the mid-1960's, drought nearly eliminated surface-water supplies that were used in the South Coast province area for irrigation, and ground-water production was increased to make up the deficit. By 1968, after 3 years of increased pumpage, the ground water in storage was drastically depleted. An estimated 1,000 hm» of the 1,500 hm3 in available storage had been withdrawn. The depletion in storage was accompanied by a decline in ground-water levels to below sed level over large areas (pi. L4). The chloride concentration in the ground water increased slightly in the more severely depleted areas, but major seawater intrusion did not occur, apparently because of a slight ground-water mound in the coastal areas and the lower hydraulic con- ductivity of the coastal part of the aquifer. Heavy rains later in 1968 recharged the aquifer, but it has never recovered to early 1960 levels. A few areas where ground-water levels were below sea level still persisted in 1976 (pi. IB), but there has been no significant in- crease in chloride concentration indicative of seawater intrusion. OPTIMIZATION OF USE OF WATER RESOURCES In general, until recent years the effort devoted to optimizing the use of water resources of the Caribbean Region has been minimal. Within Puerto Rico this lack of effort may have been due to the relative abundance of freshwater in relation to demand in most areas. In the U.S. Virgin Islands the poor quality of the ground water and the knowledge that the limited freshwater resources could not meet the demand led to reliance on seawater- desalination plants. Two major approaches are available for optimizing the use of water resources. These are conjunctive use of surface- and ground-water sources and water conserva- tion. The potential for application of such measures in the Caribbean Region is discussed separately. CONJUNCTIVE USE OF SURFACE- AND GROUND-WATER SOURCES The greatest potential for conjunctive use of surface- and ground-water Morces in the Caribbean Region may be on the island of Ptonrto Rico, where both sources are relatively plentiful. This use may be achieved by res- ervoir management, augmenting natural recharge, ground-water salvage, ground-water mining, and use of seawater. RESERVOIR MANAGEMENT Agriculture is the largest single water user in the South Coast province. The estimated ground-water withdrawal for irrigation (180 hm*/yr) constitutes almost 80 percent of the total pumpage. Therefore, the most productive efforts to solve the "water shortage" may involve an improvement of irrigation practices. To some degree, the irrigation efficiency likely could be im- proved by coordinating the activities of PRWRA with those of the Puerto Rico Sugar Corporation and by changing the priority of the functions of reservoirs serv- ing the south coast. Under present operating conditions, reservoirs are maintained at the highest stage possible for hydroelec- tric generation, thus reducing the runoff-capture poten- tial. With the available reservoirs and the implementa- tion of a more efficient water-management system, more water could be made available for irrigation. The hydroelectric-energy loss could possibly be compensated for by thermoelectric generation through burning of bagasse, the plant residue left after the juice has been extracted from sugar cane. During the 1973 fiscal year, PRWRA bought from the sugar mills (which operate from about December to April) 826 million kilowatt- hours of energy generated through burning of bagasse (Puerto Rico Planning Board, 1976). Hydroelectric generation was only about 97.5 million kilowatt-hours during the 1973 fiscal year, partly by north-coast hydroelectric plants. AUGMENTING NATURAL RECHARGE Although aquifers receive recharge by natural means, it may be practical in some areas to increase this amount artificially. Within urbanized centers the loss of rainfall infiltration capacity may be compensated for by con- struction of infiltration ponds, which may also serve for recreation. Flow into the ponds could be supplied from urban runoff or by pumpage from nearby streams. These infiltration ponds could be situated in the upland coastal areas, where coarse sediments (sand and gravel) predominate and thickness of unsaturated material and therefore storage volume is greatest. Areas of Puerto Rico that could benefit most from such modifications are those zones where urban development has decreased the infiltration capacity of aquifers (essentially the San Juan metropolitan area and Ponce). In the San Juan metropolitan area, possible sites would be the San Sebastian outcrop and areas between the haystack hills (mogotes). At Ponce the most favorable area may be near the foothills, where depth to the water table is bet- ween 15 and 20 m. Infiltration induced by this method may make it feasible to establish and continuously operate public-supply wells within city limits, thus reducing dependence on interbasin water transfer. These well fields would also be invaluable in the event of hurricane damage to centralized water-purification and distribution systems. If the recharged water is destined for domestic use, measures would have to be taken to avoid contamination with toxic substances, which may U30 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES even though ground-water development may be minimal in some areas. Within aquifers for which preliminary areal models have been constructed, monitoring net- works should be maintained to determine whether or not conditions follow those predicted. If significant deviation is detected, the cause can be evaluated and remedial measures can be taken as appropriate. Among the most important needs for improving the knowledge about aquifers in the Caribbean Region are listed as follows: 1. Better definition of conditions within the two major aquifers: knowledge needed about the following: a. Hydrologic relationship between bedrock and alluvium in the South Coast province of Puerto Rico and stream-aquifer interrela- tionships b. Extent of the artesian system in the North Coast province of Puerto Rico c. Ground-water flow within the North Coast province west of Arecibo 2. Areal studies made concerning the following: a. Ground-water flow system in Lajas Valley b. Water-balance for unstudied aquifers in the East Coast, West Coast, and Interior pro- vinces c. Water-table monitoring throughout Puerto Rico, the offshore islands, and U.S Virgin Islands d. Qualitative and quantitive assessment of saline- water reserves of St. Croix and in the coastal aquifers of Puerto Rico e. Chemical-quality data to assess the extent of contamination and seawater intrusion Besides these basic needs, research is also lacking on evapotranspiration and its relationship to soils and vegetation under the climatic conditions in the Carib- bean Region. At present it is unknown if under long- term conditions thick vegetation and plant debris aid ground-water recharge by reducing runoff, enhancing infiltration, and reducing direct evaporation of rainfall or whether they use more water from the soil through transpiration. ArchaHologkal sites, surface features, and historical notes ittdteite that water was much more plentiful at now parched areas in Puerto Rico's offshore islands and in the U.S. Virgin Islands. SUMMARY The Caribbean Region consists of the Commonwealth of Puerto Kico (8,990 km2) and the U.S. Virgin.Islands (350-kni*). It is among-the mosfdenseTy populated areas in the W6r1d, willi ail uverull population til approximate- ly 3,200,000 people. Within the past 25 years the islands liave undergone a rapid transformation from an agriculturally based economy to one dependent on in- dustrial development, tourism, and related services. Water is among the most abundant and valuable natural resources in the Caribbean Region, but its availability varies significantly in both space and time. Rainfall contributes an annual average of 1,800 mm in Puerto Rico and 1,060 mm in the U.S. Virgin Islands. Of this amount, 1,130 mm (or 64 percent) in Puerto Rico and 990 mm (or 93 percent) in the U.S. Virgin Islands is lost to evapotranspiration. The water available for use in liquid form amounts to about 5,400 hm3/yr in Puerto Rico and 24 hm3/vr in the U.S. Virgin Islands These amounts would theoretically satisfy the total water needs of both areas, which are about 919 hm3/yr and 20 hmVyr, respectively (1975). In reality, most of this flow is contributed by intensive rainstorms and is lost to the ocean as runoff. Potential for retaining a large part of this flow exists on the island of Puerto Rico, but present- ly the total usable reservoir storage capacity is only about 230 hms. In the U.S. Virgin Islands, small dams and ponds have a storage capacity of about 2 hm». Aquifers constitute a valuable water resource in the Caribbean Region. In Puerto Rico, ground-water withdrawals provide about 38 percent of the total water requirements, whereas in the U.S. Virgin Islands, they_ provide 10 percent. Excluding desalinated-water sup- plies in the U.S. Virgin Islands, ground water provides about 72 percent of the freshwater used. Of the 350 hm*/yr ground-water withdrawal in Puerto Rico, irriga- tion uses 53 percent; industry, 29 percent; and public water supply, 18 percent. In the U.S. Virgin Islands, ground water is withdrawn about equally from private wells and public water-supply wells. Based on past trends and future economic outlook in the region, estimates are that by 1985 ground-water pumpage in Puerto Rico will be about 426 hm3/yr and in the U.S. Virgin Islands, about 4.5 hms/yr. This withdrawal is the estimated maximum sustained yield of all aquifers in the U.S. Virgin Islands under natural-recharge conditions. Most large-scale ground-water developments in Puer- to Rico are in the North Coast and South Coast pro- vinces. The North Coast province contains the island's most productive aquifer, which has been undergoing rapid development for industrial water supply since 1968, when a major artesian system was tapped. The ex- tent of this artesian system is unknown, but it has been tapped within the lower part of the Cibao Formation (Montebello Limestone Member) and in the upper part of the Lares Limestone. The South Coast province aquifer consists of deep alluvial deposits. It has been ex- tensively developed for irrigation of sugarcane and for industrial water supply. Unlike the north-coast aquifer system, which has large untapped resources, this aquifer CARIBBEAN REGION U31 will support only minor future development if effective management practices are not introduced. In the U.S. Virgin Islands, the most extensive aquifer is^TEe fragmented igneous rock. It contributes little water to wells, but weighed against the costs of desalinated water, its exploitation is feasible for sup- plementing domestic water needs. The most productive aquifer consists of marl and alluvium deposits in central St. Croix. Although this aquifer contributes less than 6.3 Us to individual wells, it yields about 0.86 hnWyr to public water-supply wells and about 0.54 hms/yr to private wells. Future development of this aquifer could probably produce an additional 1.0 hm3/yr. Ground-water resources will continue to play an im- portant role in the future development of both Puerto Rico and the U.S. Virgin Islands. In order to meet future needs, it is necessary that hydrologic principles be effectively applied in managing the total water resource. Optimization of the water resources can be ac- complished through conjunctive use of surface and ground waters and through conservation practices. Op- timal use may involve artificial recharge, ground-water salvage, saline- or fresh-ground-water mining, use of seawater, waste-water reuse, and use of underground space for temporary storage of wastes, which could otherwise contaminate valuable water supplies. Efficient development of the water resources within a basin also requires a thorough knowledge of the rela- tionship that exists between surface and subsurface water. Among the most urgent needs in the Caribbean Region is a computerized data bank containing informa- tion on ground-water withdrawal, consumptive use, sur- face diversions, and such other flows necessary for water-budget estimates. These data can be used with the available knowledge of the aquifers to construct digital or analog models. Such an approach would serve to point out areas where new information is needed, aid in assigning investigation priorities, and contribute to ef- fective management of the total water resource. SELECTED REFERENCES Acevedo, G., Lugo-Lopes, M. A., and Ortiz-Velez, J., 1959. Occurrence of soil tumors nortfaMrt of tht Guanka Lagoon, Lajas Valley, Puerto Rico: University of Puerto Rico Agricultural Station Jour- nal, v. 43, no. 2, p. 103-115. Adolphson, D. G., Seijo, M. A., and Robinson. T. M., 1977, Water resources of Maunabo Valley. Puerto Rico: U.S. Geological Survey Water-Resources Investigations 76-115, 44 p. Anders, R. B., 1968, Reconnaissance of the water resources of the Central Guanajibo Valley, Cabo Rojo, Puerto Rico: U.S. Geological Survey open-file report, 18 p. Anderson, 1976, Ground water in the San Juan metropolitan area. Puerto Rico: U.S. Geological Survey Water-Resources Investiga- tion 41-75, 34 p. ———1977, Ground water in the Lajas Valley. Puerto Rico: L.b. Geological Survey Water-Resources Investigation 68-76, 45 p Arnow. T.. and Crooks, J. W., 1960, Public Water supply in Puerto Rico: Commonwealth of Puerto Rico Water-Resources Bulletin 2. 34 p. Bennett. G. D., 1972, Ground water along Rio Bucanaat Ponce, Puerto Rico, and effects of a proposed flood way on ground-water quality: Commonwealth of Puerto Rico Water-Resources Bulletin 11, 28 p. ———1976. Electrical analog simulation of the aquifers along the south coast of Puerto Rico: U.S. Geological Survey Open-File Report 76-4, 101 p. Bennett. G. D., and Giusti, E. V.. 1972, Ground water in the Tor tuguero area, Puerto Rico, as related to proposed harbor construc- tion: Commonwealth of Puerto Rico Water-Resources Bulletin 10. 25 p. Black, Crow and Eidsness, 1976, A water management plan for St. Croix, U.S. Virgin islands: Black, Crow and Eidsness. Inc.. Con- sulting Engineers, Gamsville, Fl. Black and V eaten, 1976, Water supply study for entire island of Puerto Rico, first phase: Black and Veatch Consulting Engineers. Kansas City, Miss. Black and Veatch. Domenech. R. A., and Associates. 1970, Water resources of Puerto Rico, phase II, Ground Water appraisal: Black and Veatch Consulting Engineers. Kansas City, Miss., and R. A. Domenech and Associates, Halo Rey, Puerto Rico. Bogart. D. B.. Arnow, T., and Crooks. J. W., 1964, Water resources of Puerto Rico, a progress report: Commonwealth of Puerto Rico Water-Resources Bulletin 4, 102 p. Bonnett, J. A., and Brenes, E. J., 1958, Detailed salinity survey of Lajas Valley: University of Puerto Rico Agricultural Experimen- tal Station Bulletin 111, 114 p. Briggs, R. P., and Akers, J. P., 1965, Hydrogeologic map of Puerto Rico and adjacent islands: U.S. Geological Survey Hydrologic In- vestigations Atlas HA-197, scale 1:240,000. Briggs, R. P., and Seiders, V. M., 1972, Geologic map of the Isla de Mona Quadrangle, Puerto Rico: U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-718, scale 1:20.000. Buros, 0. K., 1976, Wastewater reclamation project, St. Croix, U.S. Virgin Islands: U.S. Environmental Protection Agency. En- vironmental Protection Technology Series EPA-600/2-76-134. 244 p. Calvesbert. R. J., 1970, Climate of Puerto Rico and U.S. Virgin ! Islands: U.S. Department of Commerce Environmental Science Services Administrative Publication 60-52, Silver Spring, Md., 29 P. Cederstrom, D. J., 1950. Geology and ground-water resources of St. Croix, Virgin Islands: U.S. Geological Survey Water-Supply Paper 1067, 117 p. Cosner, 0. J., 1972, Water in St. John, U.S. Virgin Islands: U.S. Geological Survey open-file report, 46 p. Crooks. J. W., Grossman, I. G.. and Bogart. D. B., 1968. Water resources of the Guayanilla-Yauco area. Puerto Rico: Com- monwealth of Puerto Rico Water-Resources Bulletin 5. 55 p. Diaz. J. R., 1968-1974. Ground water levels in the south coast of Puer- to Rico (Guanica to Patillas): U.S. Geological Survey Data Release PR-1. San Juan, P.R. ———1973. Chemical quality of water in Caflo Tiburones. Puerto Rico, A reconnaissance study carried out in 1967: L'.S. Geological Survey open-file report (map), 2 p. ———1974, Coastal salinity reconnaissance and monitoring system - south coast of Puerto Rico: U.S. Geological Survey Open- File Report 74-1, 28 p. REFERENCE NO. 4 SCIENCES • .*.v ..•"*••?. PO NYAS-3 vol.19 ;; TUT 002 01.0-i STOXE: METEOROLOGY 0!' THE I ' l R G I X I.^LAXDS 19 5- =j The nature of the shorter-period pressure variations in relation to the weather and the general circulation are discussed below under The Upper Air and General Circulation, etc. PRECIPITATION Ram is the climatic element of most practical concern in the islands be- cause it is 131 ten insufficient to mature sugar cane in one or two seasons : a drought of six or nine consecutive months occurs every decade or so. caus- ing much hardship to the townspeople and small native farmers as well as to sugar and cotton estates and cattle ranches. Since early in the nineteenth century rainfall in the Virgin Islands has been measured in a unique unit of depth, called the "line". The reason for the adoption of this measure is not known. It is an old English measure, in which 1 inch = 8 lines (= 25.40 millimeters ). In Denmark they once used the Paris measure of 12 Linicn = 1 Touune (Paris inch) = 27.07 milli- meters — 1.0658 inches. 1 Paris line = 2.256 mm = .0888 inch = Vi44 foot, whereas the Danish ll'cst Indian (or English) line = 3.175 mm = 1% inch. It is conceivable that as many of the residents were British this "line" was adopted locally from using English rain-measuring glasses or sticks graduated in eighths of an inch. Since the American occupation inches have been used. Accuracy of the Measurements The accuracy of rainfall measurements is a difficult problem in gen- eral, and is especially serious in tropical countries.* We have already re- ferred to the lack of standards in the instruments and observation pro- cedures at Virgin Islands stations, and here we must add that where the rainfalls are frequently light and the monthly and annual totals are small the errors of measurement are greatest on a percentual basis. The common practice of measuring the catch only once each 24 hours allows some water to evaporate from the gage before it is read, particularly in a warm windy climate. The use of a funnel is common and tends to cut down the evapo- ration. Where most of the rain falls at night, it is better to read the gage in the morning, and where it falls more in the day an evening observation hour is preferable; two readings a day would be still better, and best of all the use of recording gages or the habit of reading the gage after each shower. It has been shown that a considerable difference in a given ' For .1 comprehensive discussion see Hrnnks. C F . Need tor universal standards for measuring precipitation, snowtall. anil snowcover. Truns. Meet. Int. Comm. Snow and Glaciers, Int. Assoc. Hydrol. Bull. 23: pp. 1-52. Riga. 1938. 20 SCIENTIFIC SURVEY OF PORTO RICO STONE: month's total may result at the same spot between a gage read each morn- ing and a gage read each evening. But it is difficult to estimate the magni- tude of this effect in the Virgin Islands except to say that the results from gages read only in the morning are probably somewhat lower than they would be if read only in the evening. The hours of observation at the vari- ous stations are not stated or known in many cases and at some stations they were changed from time to time. Rain gages of different diameter and different height of orifice above the ground do not give comparable catches, but it is believed nearly all the gages used in the Virgin Islands since 1870 have been of the standard 8-inch diameter with rim about 3 feet high (cf. appendix A). The wind eddying around the gage may keep away some of the rain that should go in the gage. In windy places the catch may average 20 per cent too low from this cause, but we judge from tests made elsewhere with shielded gages that this error in the Virgin Islands probably does not average over 10 per cent (i.e., readings are 10 per cent too low on average from the wind effect alone). If we may assume that this error applies roughly equally to all the gages in the Caribbean region, it may be overlooked in practical comparisons. However, the error due to wind effect increases as the wind velocity increases and therefore the catch during severe storms, hurri- canes, is apt to be more than 10 per cent too low. High wind sometimes blows the gage over resulting in loss of a large catch of rain. Occasionally during heavy rains the gage may overflow before it is read. Considering all these sources of error, it is evident that on the average the recorded rain- falls are systematically lower than the true rainfalls. In addition there may be mistakes and falsifications on the part of ob- servers, which are unsystematic in their effect on the results and largely hidden in the averages. An inspection of the daily entries and the reputa- tion of the observer are the only bases for accepting observations as genu- ine, where the stations are not under regular inspection of an efficient na- tional weather service. We have not found any record of inspections by the Danish government, and the U. S. Weather Bureau inspections have been too infrequent to be effective. General Distribution From APPENDIX TABLES 2 and 3 we note that the mean annual rainfall differs considerably at the various stations, ranging between about 35 and 70 inches. The absolute range between driest and rainiest years at these stations is not much larger, however, the extreme annual totals ranging from about 25 inches to nearly 95 inches (APPENDIX TABLE 1). If we had records from ea tremes would be inches. A rainfal The seasonal > in May or June much more prom on record indicat month; even Oct tions (see TEXT sections of St. C rainfall from no west, but from middle was agai shift in the relat south of east, wh peratures and h graphic effects. E. Taylor in 1888: 42) sugg j RICO gage read each inorn- to estimate the magni- v that the results from what lower than they ;oservation at the vari- s and at some stations ht of orifice above the >elieved nearly all the '>een of the standard endix A). The wind .ie rain that should go f 20 per cent too low where with shielded uoes not average over verage from the wind s r6i«rhly equally to rlc i in practical increases as the wind vere storms, hurri- gh wind sometimes of rain. Occasionally read. Considering all : the recorded rain- s on the part of ob- results and largely ies and the reputa- >servations as genu- of an efficient na- of inspections by m inspections have 'in annual rainfall •een about 35 and iest years at these "al totals ranging LE 1). If we had STONE: METEOROLOGY OF THE VIRGIN ISLANDS 21 Ficuix 2. Rainfall nap of St. Croa, 1921-30. (From Shaw, 1932.) records from eastern St. Croix and from the mountain tops, these ex- tremes would be greater, probably reaching from 15 to more than 100 inches. A rainfall map of most of St. Croix is shown in FIGURE 2. The seasonal distribution generally shows two maxima, a smaller one in May or June and a larger one in October. The winter minimum is much more pronounced than the summer one. The lowest monthly amounts on record indicate that severe drought conditions can occur in almost any month; even October has sometimes had less than 2 or 3 inches at most sta- tions (see TEXT TABLE 4). Rose points out that the middle and western sections of St. Croix have somewhat opposite tendencies in departures of nunfall from normal — from 1903 to 1908 the middle was drier than the west, but from 1909 to 1915 the middle was wetter, and after 1915 the middle was again the drier. This may possibly be due to a quasi-cyclic shift in the relative frequency of winds from slightly north and slightly south of east, which would be accompanied by changes in the average tem- peratures and humidities of the trade winds as well as contrasted oro- graphic effects. Forests and Rainfall E. Taylor in his "Leaflets from the Danish West Indies" (London, 1888: 42) suggests that St. Croix formerly had a greater rainfall be- SCIENTIFIC SURVEY OF PORTO RICO cause an early book on the islands by Oldendorp ( 1777) reported a greater amount of forest growtli than is now found. Although a change of climate is possible, the present condition is better explained by the known destruc- tion of the forest by the inhabitants. TEXT TABLE 5 shows no permanent change in the rainfall of St. Croix since 1852. St. John and Tortola have the most forests at present because they are too mountainous for economi- TEXT TABLE 4 FREQUENCY OF .MONTHLY RAINFALL TOTALS GREATER THA.V SPECIFIED AMOUNTS, ST. CROIX Average of 3 stations for 63 years, 1852-1914 (From Ravn) Mont* January February March April \£y June July August September October November December Number of yean with rainfall Over 20 lines (2. SO in.) 25 U 13 33 31 38 44 50 57 60 54 39 Over 40 lines (5.00 In.) I11 5 24 19 1] 22 32 IS 30 11 Over 60 lines (7.50 in.) _ _ — 1 11 9 3i 10 IS 13 4 cal sugar-cane culture, though at one time both were under considerable cultivation. There is no reason to believe that either St. John or Tortola receive much more rain than St. Thomas or St. Croix merely because they are now more forested. Indeed, the rainfall observations (cf. APPENDIX TABLES 2-6) lend no support to that notion. Orographic Effects The rainfall increases with elevation on all the islands, as residents and travelers can readily observe and as one would expect. But rain-gage sta- tion* are Jacking at high elevations, except Pearl, Mafolie. Liliendal, Wint- berg, and Dorothea. Shaw's rainfall map (FIGTRE 2) based on rainfall records (see APPENDIX TABLE 7) of sugar estates on St. Croix leaves no doubt that even moderate elevations are better watered. Yet the rate of in- crease of rainfall with elevation does not here seem to be as large as in the parts of Porto Rico where the mountains rise steeply to 3000 feet or more directly in the path of the prevailing winds. Rose suggests that the rain- fall of the islands is not as great as one would expect from the topography because the winds blow mostly parallel to the mountain trends. The reason a_i01 H xulH I O O OTQ 2 ? ("D T •> -i -, ,'. TEXT TABLE 5 AVERAGE RAINFALL FOR EACH 10-YEAR PERIOD, 1852-1911 (IN INCIIKS)* "St. Croix, Virgin Islands" = (Cliristiunstcd's Fort + KinKs Hill* + l-'u-ili-ricksirtl's Furl)/.! (From L. Smith) Period Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Year 1852-61 1862-71 1872 Sit 1K82 91t 1892 1901 1402 11 Total Average for 60 (1852-1911) • These are From "Ke|iorts t Kings Hill 1.90 .60 1.68 2.11 .65 2.36 285 .33 1.5i : 78 10 1.15 2.16 .45 1.32 2.52 2.31 1.12 14.33 11.45 10.21 years 2.38 1.91 1.70 from the same observations used in TEXT of the Virgin Islands Experiment Station, 3 12 2.06 1.43 3.27 2.15 2.52 15.57 2.60 TA»US 19 10 22 1911". was omitted from the averages for Oct. 1878 to Oct. 1888, 5.53 3.35 4.16 3.22 633 4.26 26.90 4.47 3.76 3.86 4.4S 3.97 460 3.40 24.08 4.01 , here converted inclusive. 3 51 3.10. J.37 406 542 J.47 21.95 365 to inches from i 492 4.18 4.25 4.62 4.58 5.40 28.11 4.70 the "lines' 7 2 6 5 26 5.28 4.92 6.81 6.92 36.45 6.07 1 in which 8.16 7.80 5.11 7.50 5.47 4.6S 39.38 6.56 rainfall 4.43 4.07 6.61 592 546 4.96 31.45 5.23 was measured 2.68 3.40 2.33 3.67 4.08 5.05 21.23 3.53 (8 lines = 48.61 \ 43 00 44.86'\ , 47.50*> \49.87 117.02. 281.35 46.89 1 inch). ..*?.'. 24 SCIENTIFIC SURVEY OF PORTO RICO for this may also be contained in some observations of the writer : on sev- eral occasions during his stay at St. Thomas in June, 1939 when the sum- mit of the island (1800 feet) was visited, he noticed that any large cumulo- nimbus cloud that had been initiated by forced ascent of the wind over the island would lean to the leeward so that most of the rain falling from it would fall on the ocean surface somewhat to the lee of the island. In other words the orographic influence on the rainfall was not fully enjoyed by the island itself owing to its small size and narrow form. This observation is confirmed (oral communication) by Sergeant Davidovic. the Aerographer stationed at the U. S. Marine Corps Fleet Air Base on St. Thomas in 1939. In general the annual rainfall does not seem to increase more than about 10 inches between sea level and 1000 feet elevation, but some of the lower stations have as much rain as places high up on the leeward slopes or in high protected valleys (compare Adrian and Cinnamon Bay, or Barracks and Liliendal, in the same years) (APPENDIX TABLE 2). In generally rainy years or months the rainfall differences between stations of different ele- vation are much greater than in generally dry seasons. At the U. S. Marine Corps station on Lindbergh Bay three rain gages have been set a few hundred yards apart in a line from the water to the foot of the mountain. These gages show a decided increase in rainfall (AP- PENDIX TABLE 12) as the mountain is approached, although they are all about at the same elevation. This demonstrates how sensitive the rain- producing process is to the topography. For this^reason, within the hilly town of Charlotte Arnalie qr_pjf " _ _ probably varies considerably (up to 5 inches ?) from block to block : hence records taken at different spots in such a town cannot justifiably be com- bined as if from one station. Likewise different parcels of an estate often have very different rainfall (e.g., Eden, Emmaus, Caroline; Adrian, Su- sannaberg). We have not attempted to construct rainfall charts of St. Thomas and St. John owing to the non-homogeneity of the records. Shaw's map of St. Croix ^ncintB 2) is based on a homogeneous though short (10 years) series of 26 records from the flatter parts of the island, which should give a reliable and consistent pattern. Year to Year Variation The variability of the mean annual rainfall is of prime economic conse- quence because in over half the years the actual rainfall is well below the normal rainfall,* which is just about sufficient for an annual yield of sugar * It is characteristic of the frequency distribution of either daily, monthly or annual rainfalls, that the most frequent ralue (.modi) i* generally much less than the average, and in some cases the zero value is most frequent. .STO.V/J; ME! cane, long the chief cro discusses this problem low). Du Tertre and C the poor crops of 1841 1923 to 1924 were dut trary to the impressioi evidence that the raini to century (see Forest has not been scientific show long quasi-perio rainfall. These undoui enough to reveal any I near the critical limit f tuations are important understanding of the for the fanners merely attempts to forecast tl derived from analysis for long-range foreca: solutions offered do no plicability, however pr The most successful r places, none of which r The diurnal distribt; greater amount of rair loe's observations at < Tidende", 1888. He gi NIGHT AND Month (13«8) July August September * In lines; 8 lin The frequency of n is probably not so proi heavier. TLi 01- TO RICO STO.VE: METEOROLOGY OF THE VIRGIN ISLANDS 25 ns of the writer : on sev- une, 1939 when the sum- d that any large cumulo- ent of the wind over the the rain falling from it "e of the island. In other not fully enjoyed by the orm. This observation is vidovic. the Aerographer on St. Thomas in 1939. -crease more than about n, but some of the lower ic leeward slopes or in imon Bay, or Barracks •E 2). In generally rainy fations of different ele- ns. .;a B^three rain gages ^ from the water to the icrease in rainfall (AP- although they are all iow sensitive the rain- iason, within the hilly verage annual rainfall n block to block; hence not justifiably be corn- els of an estate often Caroline; Adrian, Su- :s of St. Thomas and Is. Shaw's map of St. ugh short (10 years) id, which should give ime economic conse- :alJ is well below the annual yield of sugar onthljr or annual rainfall*, rape, and in tome cue* the cane, long the chief crop, and the cane yield suffers accordingly (Dr. Shaw discusses this problem with respect to St. Croix, in paragraphs quoted be- low). Du Tertre and Oldendorp mention great droughts in 1661 and 1753 ; the poor crops of 1841, 1864, 1869, 1872 to 1877, 1891, 1892, 1899, 1904, 1923 to 1924 were due to low rainfall (see TEXT TABLES 20 to 23). Con- trary to the impression ot many residents and travelers, there is no real evidence that the rainfall is slowly and steadily decreasing from century to century (see Forests and Rainfall). The question of cyclic variations has not been scientifically studied here, but results elsewhere generally show long quasi-periodic fluctuations of considerable amplitude in the rainfall. These undoubtedly exist here too but the records are not long enough to reveal any but the shortest "cycles". The average rainfall is so near the critical limit for sugar cane that even the small short-period fluc- tuations are important. It does not contribute much either to fundamental understanding of the variations nor to practical precautionary measures for the farmers merely to describe the rainfall curve as quasi-periodic. All attempts to forecast the fluctuations by means of extrapolating "cycles" derived from analysis of past records have been failures. Scientific bases for long-range forecasting are being sought in many directions but the solutions offered do not yet give results of practical value and general ap- plicability, however promising the method or enthusiastic the advocates. The most successful results so far are for certain special conditions and places, none of which have been in the West Indies. Diurnal Variation The diurnal distribution of the rainfall, as at San Juan, shows a much greater amount of rain by day than by night, judging from Mr. A. Wal- loe's observations at Charlotte Arnalie, published in the "Set. Thomae Tidende", 1888. He gives the following figures. TEXT TABU 6 NIGHT AND DAY RAINFALL, CHARLOTTE AMALIE, 1888* Month (1838) Total Bydar Bynicht July August September 38.4 77.2 69.0 26.8 55.9 44.6 11.6 21.3 24.4 • In lines; 8 lines = 1 inch. The frequency of rain is no doubt also greater by day but the contrast is probably not so pronounced because the intensity of the day showers is heavier. T U < Oil 26 SCIENTIFIC SURVEY OF PORTO RICO At sea the rainfall frequency is a maximum at 6 A.M. with a secondary maximum at about 10 P.M. The amplitude of this daily variation is pre- sumably smaller than the one observed over the islands, where the maxi- mum comes in the afternoon. It is very likely that the sea maximum at 6 A.M. affects the islands, or at least their shoreward margins, causing a secondary maximum at that hour. Xo hourly observations are available from the islands but the sunrise shower seems to be recognized by the residents as a more or less regular phenomenon. The daily double period in the rainfall is of course reflected in the cloudiness (TEXT TABLE 17) and in the frequency of thunderstorms. Intensity and Frequency The rainfall in this low latitude and oceanic situation is entirely of the shower type, and therefore it is of great practical importance to know how frequently showers occur, how long they last, how much rain falls per shower, and what are the average and maximum rates of fall over short periods of time. Unfortunately systematic observations using recording rain gages were begun in the islands only very recently, so we are forced to infer much from the usual rainfall observations which give only monthly totals and numbers of rainy days. The average rainfall per rain day (APPENDIX TABLES 10 and 12; FIGURE 10) indicates some important characteristics. The "showers" of the winter and spring seasons are characteristically brief and light, often mere sprinkles, from cumulus clouds of small or moderate size and spaced by large intervals of blue sky (cf. TEXT TABLE 9). Sometimes "norther" effects cause a low overcast cloud deck with driz- zling rain punctuated by occasional heavier showers, which condition may persist a day or two. However, very heavy rains up to j2 or fl ityh^ in a day have fallen even in the driest months. In the "rainy season", from "May to M"vgB^ffTr h^vifr and more enduring showers, w't-h squalls £"" fliunder and Bjfetpioe at times, are to be often : nf r . —— - -- 1| I I - • • • • - • • f"-"V ..111=11. .1L least one shoiwr Of some sort then falls almost every day. Heavy rains lasting as much as 6 or 8 hours, even with brief intermissions, are normally very rare, but passage of a hurricane withinJJO nrjnQjrpjlfs rf*n <•»"«* «»nnr- mous rainfall totals (overJO IhchgsjJflL? flny "r two frpyn virtually *•""- dnuous Hnwflpntirs, The high wind during hurricane weather adds greatly to the destructive effect of the rain. Some significant deductions can be made from the results of the re- cording rain gages, in spite of the short period they have been in use. At the Marine Barracks of Bourne Field on St. Thomas a recording rain STO.VE: METEOROL gage has been operated since 1 TABLE 12 and FIGURE 10) indi and also per rain hour for eact fall during any 24 hours of th teresting relation because in tl places we can assume that tin tabulated by the U. S. Weatlu basis for estimating the averat, Since February 1940. the S< rainfall rates monthly from rei estates on St. Croix. An abstr and 8. Although the period of averages or extremes likely to study of the tables reveals a cb rainfall and the maximum int the average intensities. This i: showers probably have more numerous lighter showers. Tl average intensity to be great' months. It will be noted, howi months appears to be as higl whereas the total rainfall is u the spring. This is a curious the greater frequency of hail the late summer and-autumn. < tensity of rainfall will actual! because of hurricanes. The in: excluded, winter and spring ? tensity as the autumn rains, bv riods, as shown in TEXT TABL greater in the "rainy season" t to infer to what extent this islands, as the topography m well as the totals, but the Bour to show similar features to the Any practical interpretatic Virgin Islands, especially on that a large proportion of the i (see TEXT TABLES 9 and 10). I rain gages and they augment significance for crop growth F PORTO RICO num at 6 A.M. with a secondary ie of this daily variation is pre- er the islands, where the maxi- ikely that the sea maximum at r shoreward margins, causing a )iirly observations are available seems to l>e recognized by the .ienon. The daily double period loudiness (TEXT TABLE 17) and •quency mic situation is entirely of the .ctical importance to know how last, how much rain falls per imi'"i rates of fall over short 01 ,-ations using recording . ery recently, so we are forced bservations which give only The average rainfall per rain 10) indicates some important seasons are characteristically i cumulus clouds of small or - of blue sky (cf. TEXT TABLE jvercast cloud deck with driz- howers. which condition may rains up to 2 or 3 inches in a In the "rainy season", from ing showers, with squalls or ;pected much more often; at nost every day. Heavy rains f intermissions, are normally i or 100 miles can cause enor- v or t\vo from virtually con- rricane weather adds greatly from the results of the re- ' they have been in use. St. Thomas a recording rain STOVE: METEOROLOGY OT THE VIRGIN ISLANDS 27 gage has been operated since 1935. An analysis of the results (APPENDIX TABLE 12 and FIGURE 10) indicates that the average rainfall per rain day and also per rain hour for each month is proportional to the greatest rain- fall during any 24 hours of the corresponding months. This is a very in- teresting relation because in the absence of recording rain gages at other places we can assume that the "greatest rainfall in 24 hours", which is tabulated by the U. S. Weather Bureau for all its stations, gives a rough basis for estimating the average intensity of rainfall per clay and per hour. Since February 1940, the Soil Conservation Service has been tabulating rainfall rates monthly from recording gages at Anna's Hope and Jolly Hill estates on St. Croix. An abstract of the results appears in TEXT TABLES 7 and 8. Although the period of observation is too short to give any definite averages or extremes likely to occur, the figures are already significant. A study of the tables reveals a closer correlation by months between the total rainfall and the maximum intensities than between the total rainfall and the average intensities. This is not surprising because one or two intense showers probably have more effect on the monthly totals than the more numerous lighter showers. There is nevertheless some tendency for the average intensity to be greater in the rainier months than in the drier months. It will be noted, however, that the average intensity in the spring months appears to be as high as or higher than in the autumn months, whereas the total rainfall is usually much greater in the autumn than in the spring. This is a curious fact which we have already suspected from the greater frequency of hail in the late spring and early summer than in the late summer and-autumn. Over a period of many years the average in- tensity of rainfall will actually be greatest in the autumn or late summer because of hurricanes. The important conclusion is that, if hurricanes are excluded, winter and spring showers probably have as great average in- tensity as the autumn rains, but the maximum rates of rainfall in short pe- riods, as shown in TEXT TABLES 7 and 8, are generally two or three times greater in the "rainy season" than in the winter and spring. It is impossible to infer to what extent this conclusion is justified for all parts of the islands, as the topography may greatly affect the rainfall intensities as well as the totals, but the Bourne Field results (APPENDIX TABLE 12) seem to show similar features to those of Anna's Hope and Jolly Hill estates. Any practical interpretation of the average rainfalls reported in the Virgin Islands, especially on St. Croix, should take into account the fact that a large proportion of the rain falls in light showers and brief sprinkles (see TEXT TABLES 9 and 10). Many of these light rains are measured in the rain gages and they augment the total rainfall out of proportion to their significance for crop growth and for vegetation because they barely wet TU" 28 SCIENTIFIC SURVEY OF PORTO RICO TEXT TABLE 7 RAINFALL INTENSITIES MEASURED AT STATION SCS No. 18 F. S. A., JOLLY HILL ESTATE, ST. CROIX, V. I. (From U. S. Soil Conservation Service) Month 1940 February March April May June July August September October November December 1941 January February March April Total Rainfall. inches 0.90 0.52 1.97 7.10 3.05 2.14 5.05 4.19 7.47 7.15 3.47 1.97 0.21 1.33 2.28 Total Duration, hours* 15.02 1.92 6.42 30.00 8.10 5.07 12.37 12.65 22.45 25.37 20.25 5.02 0.80 1.13 9.45 Average Intensity, in./hr. 0.06 0.27 0.31 0.24 0.38 0.42 0.25 0.33 0.33 0.28 0.17 0.39 0.26 1.17 0.24 Maximum Intensity for Different Intervals S rain. 1.00 2.00 3.50 2.00 5.00 3.00 7.00 4.50 5.00 3.10 2.00 1.50 3.75 10-min. 0.75 1.50 2.00 1.50 3.50 1.75 5.00 2.75 3.50 2.25 1.75 1.00 2.50 20-min. 0.35 0.80 1.40 0.90 2.80 0.95 3.40 2.80 2.40 1.60 0.90 0.50 1.40 60-min. 0.13 0.50 1.10 0.55 1.30 0.30 1.40 1.70 1.45 0.85 0.40 0.18 0.56 1 20-min. _ _ 0.28 0.70 0.30 0.65 0.15 0.75 1.05 0.90 0.45 0.20 - 0.30 STONE: METE the vegetation and the t quickly evaporated by th PERCENTAGES OF 1 CHF (Fr Month • Intensities of ten than 0.10 in./hr. are not Included. TEXT TABLE 8 RAINFALL INTENSITIES MEASURED AT STATION SCS No. IS F. S. A., ANNA'S HOPE ESTATE, ST. CEOIX, V. I. (From U. S. Soil Conservation Service) January February March April M?y June July August September October November December Year Month 1940 January February March April May June July August September October November December 1941 January February March April Total Rainfall, inches OJJ 2.09 0.99 1.55 2.8* 1.51 1.17 1.7S 5.24 8.43 6.05 2.36 3.67 0.19 1.05 2.48 Total Duration, hours* 2.77 17.18 4.92 4.20 15.05 4.60 4.23 7.48 6.67 22.05 14.67 14.10 12.25 2.50 2.83 7.25 Avenge Intensity, in./hr. 0.13 0.12 0.20 0.37 0.19 0.34 0.28 0.23 0.82 0.38 0.41 0.17 0.30 0.08 0.37 0.34 Maximum Intensity for Different Interval* 5-min. 10-min. 20-min. 60-min. 1 20-min. _ 1.80 1.00 3.50 2.00 3.00 1.00 3.00 7.00 4.00 7.00 1.50 4.00 — 1.50 4.00 _ 1.25 0.75 1.75 1.50 2.25 0.75 2.00 5.00 3.00 5.50 1.00 2.50 — 1.00 3.00 — 0.75 0.35 1.20 0.80 1.20 045 0.80 4.20 2.00 3.30 0.45 1.60 — 0.50 2.60 — 0.30 0.13 0.80 0.40 0.40 0.13 0.30 2.30 0.80 1.10 0.18 0.60 — 0.20 0.92 * 0.18 — 0.43 0.25 0.20 _ 0.15 1.18 0.50 0.60- 0.38 — 0.15 0.48 AVERAGE AND EXTRE: • Intensities of less than 0.10 in./hr. are not Included. Month January February March April May June July August September October November December Year • These figures are not sunn < in the period covered by the JO SClEXTiriC SL'Rl'EY OF PORTO RICO Evaporation The actual water loss from the ground by evaporation and by transpira- tion of plants is probably high, judging from the general weather condi- tions and from the measures of evaporating power of the air made at the Experiment Station (see APPENDIX TABLE 8). Consequently, the roughly 45 inches of measured average annual rainfall in the Virgin Islands is by no means the equivalent for plant growth of 45 inches of measured pre- cipitation in rainier parts of the West Indies or in the southern United States. Thunderstorms, Squalls, and Hail Thunderstorms occur, as in Porto Rico, chiefly from July to October, according to the records at Christiansted and Bourne Field (TEXT TABLE 1 and APPENDIX TABLE 12). Schoinburgk in 1837 reported that 5 to 10 per cent of the days in a year had thunderstorms, mostly in September and October, which roughly agrees with the Christiansted data, although at Bourne Field more of the storms occur in July and August. Most storms probably occur in the afternoon, as at San Juan. They are apt to be squally and inflict wind damage at times, but lightning damage is usually slight. Squalls are sometimes associated with heavy showers and probably with most thunderstorms. The familiar downrush of cold air under a thunder- storm or tall cumulonimbus cloud can be so violent as to capsize small boats and damage dwellings, trees, and crops. When the observer is located on the sunny side of the cloud, it may appear white until after the squalls reach him, giving rise to the term "white squall" of the West Indian na- tives ; but when the observer is under or on the shaded side of the cloud. it appears very dark and ominous, so the accompanying gusts are called "black squalls". White squalls are also reported without heavy clouds nearby, but these are merely gusts when the trades are blowing strongly. The Wept Indian sailor well knows that the squalls are apt to be especially violent lad dangerous to boats along a coast which rises to high mountains imme^kfcdjr back of the shore. ffaSu rarely reported and most residents spend a lifetime in the islands without seeing any. There are enough authenticated reports to leave no doubt that it falls at least every few years, even several times in some years in which conditions are favorable for it. Much hail, with cold and rainy weather, occurred in Virgin Gorda in January 1833. according to Schom- burgk, who also wrote of hail on the north side of Tortola in November 1829. Knox mentions that hail as big as hen eggs fell in St. Croix on April 13, 1844; and that a Mr. Xissen told him of a hailstorm at St. STONE: METL Thomas on May 13, 18. St. Thomas in 1938. Alt early summer, the cases ter and spring; perhaps thus more likely to be rei Chemical analyses of Station from 1911 to 1^ tained an average of 9 nitrogen in the form of These figures varied gi The amounts do not see appear to depend on the that they are related to t These chemical constitt soil and the nourishmen W Owing to the small at ration, and the few per obtain domestic water < and stored in cisterns, a crete to catch rain for strict economy in use ot Shallow dug wells arc pumped for flushing t stocked with "mosquit spread chiefly by most of La Grange plantatio St. Croix was started but not on a scale suffic not yet been tried. Stor on which it was used f o Temperatures in th Porto Rican stations < small land area availal RICO T. CHOIX, V. I. STONE: METEOROLOGY OF THE VIRGIN ISLANDS 29 the vegetation and the top of the soil and do not sink into it, and so are quickly evaporated by the sun and wind. for Different Intervals ™°- W-rain. 120-min. 30 40 J.90 ' 80 )S 10 '.0 0 60 0.13 0.50 1.10 0.55 1.30 0.30 1.40 1.70 1.45 0.85 0.40 j.ia 0.56 TEXT TABLE 9 PERCENTAGES OF DAYS WITH SPECIFIED AMOUNTS OF RAINFALL. CHRISTIANSTED, ST. CROIX, 1852-1907 (From Willaume-Jantzen and Ravn) 0.28 0.70 0.30 0.65 0.15 0.75 1.05 0.90 0.45 0.20 0.30 Month January February March April May June July August September October November December 0-5 mm (0-0.20") 67 64 66 55 56 46 55 54 45 44 48 52 > 20 mm (0.79* or more) 5 3 4 16 10 14 10 If 15 18 12 8 > SO mm (1.97- or more) 0 0 0 2 4 3 2 4 4 7I 2 Year 54 11 Caoix, V. I. Different Intervals '• 60-min. 120-mio. TEXT TABLE 10 AVERAGE AND EXTREME NUMBERS OF DAYS WITH RAIN, CHRISTIANSTED, ST. CROIX, 1852-1907 (From Willaume-Jantzen) 0.30 „.,. £8 g-3 0.40 0.20 0.13 0.30 o.lS f§ °» UO 0.60 0.60 0.20 0.92 0.38 0.15 0.48 Month February March Anil M.7 June July August September October November December Mean 11 9 6 7 11 10 11 11 13 12 14 13 Highest in any one year 20 23 14 13 26 20 17 17 19 19 20 19 Lowest in aay one year 1 0 2 3 4 4 4 6 6 4 6 Year 128 177* * These fifures are not sums of toe columns above, but are the extreme totals on record for ujr one year in the period covered by the table. t").t 16 REFERENCE NO. 5 CLIMATOGRAPHY OF THE UNITED STATES NO. 60 Climate of Puerto Rico and Virgin Islands noaa NATIONAL OCEANIC AND /ENVIRONMENTAL/ NATIONAL CLIMATIC CENTER ATMOSPHERIC ADMINISTRATION/DATA SERVICE / ASMEVILLE. N.C. REPRINTED JUNE 1982 TUT 002 01.1^ Due to the small size of the islands and the location of all stations within a few miles of the water, the mean daily range is quite small. It varies from 9.1° at Charlotte Amalie to 15.1'F at Wintberg. For these same reasons extremes of temperature are not as great as they are in Puerto Rico, and relatively few days have temperatures of 90° F or above. Since the extent of land areas is small, the air passage over land is quite short and there is not sufficient time for extreme heating to take place. On St. Croix, Annas Hope has had a temperature as high as 99° F. During the warmest months, maximum temperatures average about 87° to 89° F, with nighttime temperatures falling to about 74° to 78° F, and a little lower at the higher elevations. In the winter, daily maximum temperatures are generally in the low 80's and nighttime minima in the high 60's or low 70*s. The highest mean maximum temperatures are found in August, while the lowest mean maxima fall either in January or February. The lowest mean minimum temperatures are observed in January and February, and the highest mean minimum temperatures are generally in July or August. DROUGHT - Drought in the Virgin Islands occurs about as often and is just as damaging as it is in Puerto Rico. None of the three islands has any significant running rivers or streams and only St. Croix has an underground water source in a few sections. Water for irrigation is not available in quantity at any time. Large storage reservoirs do not exist so the Virgin Islands are, to some extent, more at the mercy of "Mother Nature" than is Puerto Rico where there are adequate facilities for water storage. HAIL - In the U. S. Virgin Islands, hail is even less frequent than in Puerto Rico. In January of 1969 a severe local hailstorm with hailstones up to 1 1/2 inches in diameter occurred. This was the first hailstorm on record in the U. S. Virgin Islands. 20 TUT 0-rographic lif tingof the moisture laden jlr over the hilly terrain of these islands is the most frequent cause of~rain£aj.l«' However, due to the smaller el«vatIons"and smaller size of the islands, there is a less marked variation in annual amounts. The larger mean annual totals are between SO and- 60 inches at the higher elevations, and the variation between the greatest and least average value is not as marked as it is in Puerto Rico. Clouds formed by forced ascent of the wind over small and narrow islands, as is the case for St. Thomas and St. Croix, lean to the leeward, so that most of the rain from them falls in the ocean to the lee of the island. Easterly wave passages are important contribu- tors to the rainfall of the Virgin Islands during the months from May through November. Like Puerto Rico, the U. S. Virgin Islands lie in the path of the tropical storms and hurricanes which form over the ocean to the east of the Lesser Antilles. As in Puerto Rico, they are relatively infrequent. While cold frontal passages affect the rainfall regime of the Virgin Islands, the frequency of fronts is less and their intensity is more likely to be diminished and less effective than in Puerto Rico. Annual rainfall values indicate differences in rainfall from location to location with higher elevations generally receiving greater amounts. On St. Thomas and St. John, on the basis of the limited data available, annual ^averagga of v>afut»qn_40_and 60 inchesjigpear reasonable. On St. Croix there is a more noticeable variation from place to place. This Island has the greatest annual rainfall, in excess of 50 inches in the northwestern corner. There are some indications that stations in a small area along the central portion of the southern coast of St. Croix receive about 40 to 45 inches. A narrow, finger of between 25 and 35 inches extends northeast to southwest over the flatlands south of the hills in the western portion of the Island. Annual rainfall averages less than 30 inches in the eastern end of St. Croix, possibly as low as 20 inches. As in Puerto Rico, there is no sharply defined wet-dry season relation- ship. Records available for the three islands indicate a relatively wet-relatively dry season distribution similar to that found in the southern portion of Puerto Rico. The relatively dry period extends from about December through June. Occasionally, quite heavy rainfall occurs during the so-called drier months. The driest month of St. Thomas and St. John usually is February or March and the wettest month September or October, as in the southern sections of Puerto Rico. On St. Croix, the month with the heaviest rainfall, on the average, ranges from September through November. The number of days with measurable rainfall over the Virgin Islands, baapi on a few known-to-be reliable stations, ranges from a little less than 200 days annually at the higher rainfall stations to less than 100 days annually at the stations with lowest rainfall. As in Puerto Rico, one of the most striking features of the temperature regime in the U. S. Virgin Islands is the relatively small variation from the coolest to the warmest months, ranging from about 5° to 7°F. 19 TUT comfort or discomfort, between economic success or failure, or between safe and compatible building design can be a delicate one. Through effective planning and intelligent application of climatic considerations to life in the Caribbean, man can truly say he has found his tropical paradise. U. S. VIRGIN ISLANDS Location; The U. S. Virgin Islands are composed of three major islands, together with a number of smaller islands and cays totaling about 50. The three of primary importance are: St. Thomas, where the capital is located; St. Croix, the largest; and St. John, the smallest. These islands follow Vieques Island and Culebra Island in the path of the Lesser Antilles toward South America. St. Thomas lies some 38 miles east of Puerto Rico and about 1,500 miles southeast of New York. St. John lies a few miles east of St. Thomas and St. Croix is located about 40 miles south of St. Thomas and St. John. With an area of about 28 square miles, St. Thomas is the second largest of the U. S. Virgin Islands. This island lies between latitudes 18°23'N and 18°18'N and longitudes 65°03'W and 64°50'W. It is about 5 miles from its northernmost to its southernmost points and a little more than 12 miles from its eastern to western extremities. The smallest of the three principal islands is St. John, with an area erf only about 20 square miles. It is also the least populated. St. John lies between latitudes' 18°23'N and 18°18'N, and longitudes 64°48'W and 64°40'W. This island extends about 5 miles from its northern to southern- tips and about 8 miles from its easternmost to westernmost points. Somewhat apart from the others, the largest of the three islands is St. Croix which has an area of 84 square miles. It lies between lati- tudes 17°47'N and 17°41'N, and longitudes 64'54'W and 64°34'W. The Island extends some 19 miles from east to west and 6 miles from north to south. Topography: sj^jninmqg tiff" an^ejctremely^irregular^oastline and is very hilly with practically no f latlandT^ The~ Highest hills are generally found nreaf the-center of the Island, with Crown Mountain at 1,550 feet the highest point. The Island is relatively small and many of the peaks rise above 1,000 feet. This results in rather steep slopes over all the island, so that rainfall runoff is quite rapid and there are no per- maneni.• 14^1 1 ' •;») Ji Thomas, St. John has an extremely irregular shoreline and a very Hilly topography. It has a number of peaks over 1,000 feet, topped by Bordeaux Mountain at 1,297 feet in the eastern portion of the island. Slop«» *r« quite steep over all of the island, and there are very few areas of flatland. There are no permanent rivers or creeks. 17 St. Croix is the largest of the three U. S. Virgin Islands. The topog- raphy is somewhat different from the other two with a broad expanse of low, relatively flatland running along the southern two-thirds of the Island. A range of hills, ranging in elevation from about 500 feet to more than 1,000 feet, .topped by Mount Eagle at 1,165 feet, runs along the northern coast. In the eastern end of St. Croix is found another group of slightly lower hills with a maximum elevation of about 860 feet. The relatively small area covered by hills on St. Croix results in rather steep slopes down to the Caribbean in the north and to the level areas to the south. Agriculture is not as important in the U. S. Virgin Islands as it is in Puerto Rico. St. Croix is the only one of the U. S. Virgin Islands with any sizable expanse of flatland suitable for farming. Here sugar cane, which was the principal crop, has been abandoned. Subsistence crops are now a minor effort. Some cattle are raised for milk and meat. In St. Croix, industrial growth has become a significant factor in the island's economy. With the downgrading of agriculture, industrial complexes have been expanded to include the petrochemical industry and refinement of aluminum. Light industrial plants and the manufacture of rum are the other industrial activities in St. Croix and St. Thomas. St. John has no industrial development and remains primarily a National Park. Tourism is the biggest factor in the Virgin Islands economy. It has, over the past years, undergone a vast increase in the numbers of cruise ships, especially at St. Thomas and St. Croix. Hotel facilities have been increased on both islands. One of the principal causes of concern in the U. S. Virgin Islands is the short supply of water. Rainfall, while above 40 inches annually over most of the area, is insufficient. This is due partially to a high evaporation rate and the rapid runoff from the steep slopes on St. Thomas and St. John and, to a certain extent, on St. Croix. In an effort to utilize available water efficiently, most hones and business establishments catch rainwater on the roofs and pipe it to cisterns. The runway at the airport at St. Thomas is also used as a catchment area. On St. Thomas and St. John it is common to see the entire side of a hill cemented to act as a catchment area. Generally, during the drier portion of the year, it is necessary to carry water by barge from Puerto Rico. Installation of a sea-water distillation unit on St. Thonaa and St. Croix has helped alleviate the water shortage but water still mains a significant factor in the development of the island's eco*My. Rainfall in the U. S. Virgin Islands is of the same nature as that in Puerto Rico, falling most frequently in the form of brief showers. The rainfall-producing mechanisms are essentially the same as in Puerto Rico except in the matter of degree. 18 TUT 002 01.22 REFERENCE NO. 6 K TAT-02-F-04642 TUTU WELL SITE POTABLE WATER ALTERNATIVES REPORT ANNA'S RETREAT, ST. THOMAS, U.S. VIRGIN ISLANDS Prepared For: Carlo* E. O'Neill, P.E. OSC Luis E. Santo*, OSC Air and Hazardous Substance staff Caribbean Field Office U.S. EPA, Region II Santurce, Puerto Rico and Bruce Sprague, Chief Incident Response and Prevention Section U.S. EPA, Region II Edison, Wev Jersey 08837 Prepared By: Rodolfo Hafner, TAT II Ja»es Kanfreda, TAT II Region II Technical Assistance Team Weston/SPER Division Edison, New Jersey 08837 December 1988 0124 appear to be sufficient land available to increase the cistern volumes laterally. The only way the volume could be increased is by making deeper cisterns. This operation would require the shoring of the existing homes and apartments, therefore, the possibilty of structural damage to these residences. 2.0 SITE DESCRIPTION AMD CONDITIONS 2.1 Site Background and Conditions The Tutu Hell site is located at the eastern end of the Island at the Anna's Retreat Section of St. Thomas (see Figure 2-1 page 5). Most of the wells are used for public drinking water supply. The wells appear to be drilled into the Turpentine Run aquifer. On, or about July 7, 1987, Mr. Eric Tillett, contacted the U.S. Virgin Islands (U.S.V.I.) Department of Planning and Natural Resources (DPNR) regarding an odor emanating from the raw well water on his property located at Anna's Retreat, St. Thomas, U.S.V.I. On July 16, 1987, the USEPA received a request from the DPNR in St. Thomas, for sampling and analyses of several wells in Tutu. On July 21, the USEPA and its Technical Assistance Team (TAT) contractor, Roy F. Weston, Inc., mobilized to St. Thomas, to perform sampling on the drinking water wells suspected of being s contaminated. These wells were also reported to have a strong, unpleasant odor and were found to be contaminated with hazardous substances. The EPA and its Technical Assistance Team (TAT) in coordination with DPNR, initiated sampling of wells in the affected area in July 1987. The test results showed the presence of high concentrations of gasoline and chlorinated organic compounds. Four wells: Elgin, Four Winds, Harthman, and Virgin Islands Housing Authority (VIHA) were closed down by order of DPNR due to high VOC concentrations. Several of the wells in this area are major commercial well services used for public drinking water supply, therefore, the incident was classified as major, and the DPNR Commissioner requested the EPA to assume the role of Lead Agency. The well locations can be seen in Figure 2-2 page 6. A Texaco station, located opposite the Tillet Well, is suspected as a possible source of contamination. A Petrotight test conducted on the underground storage tanks at this facility indicated leaks in two of the three tanks. These failures may have contributed GREAT NORTH SIDE FRENCHMANS BAY IUT OO2 0126 SPIU. PREVENTON. EMEflGENCY RESPONSE DIVISION la to. andCi i wvalCF ItrdMolofr lac. CC>>o«o« * ^ •Mm GARLOS O'NZILL TATm R. HAFNZK FZ60XX 2-1 SITS LOCATION HAP ! TDTU ST. THOKAS \ U.S. VIRGIN ISLAKDl 13.4 •1X2 •1+ •19 2.3* 3.1. NO. WELL NAME NO. WELL NAME I 2 3.1 &2 H 4.J 4J5 4.3 3 6 I ? « » 10 11 BRYANS BOOBICUCS HARTHUAN BAKERY BABTSUAN BAKERY BABTHMAN BAKERY CENT ECUN 1 GENE ECUN 2 GENE ECUN 3 BARVEY-S S^^C^£*S MA7BUS-S SMITH'S FRANCOIS TTLLETS RAMSCy-S T^"r»VT/»mr i xi 12.: 12-2 13.1 13-2 13.3 13.4 14 19 16:?.i 1T^ 17.3 18 19 ie> •34^ 4 VINOS 1 4 VINOS 2 VTRA i VIRA2 VZHA3 TOA 4 AL?EA LEONARD OEMITBf OENCS OEVCON 1 OEVCON 2 OEVCON 3 OEOB LOOCHABT ^PN , wP 8*' I7J IB _ HOOK :MANC i •** i<7T«aMMmar *«e- CCXw^wi *.' cvOx , tac. CARLSS 0'!TErLL TUT 002 0127 7.^B^S^S^S^ •^••MiMMH I7IGO8Z 2-2 jWgLL LOCATIOH )CL? ITLTU ST. THOMAS U.S. VTRCIN ZSZAMT to the groundvater pollution problem, resulting in the contamination of nearby veils. Another suspected source of contamination is the Tutu Esso gas station. This facility stores waste oil in an underground storage tank. The facility has had problems in the past with leakage from their underground gasoline storage tank and is suspected of using solvents in the mechanic shop. At the time of inspection, the nature of the problem) had not been determined. Both the Texaco and Esso gas stations are upgradient from the affected veils which are being supplied vith vater. EPA continued its efforts towards the identification of; affected veils in the area, customers vhich had received vater from contaminated veils, and possible alternate vater supplies and remedial action alternatives. A testing program of veils located outside of the known area of contamination was conducted to evaluate those areas as possible alternate water supply sources. Sampling of cisterns served by the contaminated wells was also performed. EPA directed the Emergency Response Cleanup Services contractor (ERCS) to; clean and disinfect the five (5) cisterns which had tested positive for PCE, modify the existing hove plumbing, disconnect the contaminated wells, and dispose of the contaminated water. At EPA's direction, ERCS also contracted a local water hauler to deliver uncontaminated drinking water to the cisterns by tank truck. A well sampling program was established by the EPA to monitor the wells at the Tutu site for a OIM year period. Nine potential responsible parties have been identified. These facilities included three gasoline service stations, two vehicle maintenance repair shops, two territorial government agencies, one dry cleaner and one abandoned gasoline service station. EPA has identified Texaco as a viable potentially responsible party, based on the results of a soil/gas survey conducted on the Texaco Property under order from OPNR and under the supervision of EPA. The survey found total hydrocarbon concentrations up to 690 ppm of benzene. EPA is continuing its efforts to identify potential responsible parties. 2.2 Topography and •St. Thomas is the most northwest island of the U.S. virgin Islands and the second largest. The island is approximately 14 miles long and 2 to 3 miles wide and has an area of 32 square miles. The land surface is almost entirely sloping and extend seaward from a central ridge, 800 to 1,200 feet high, running the length of the island. The slopes, which commonly exceed 35 degrees, are dissected by numerous stream courses of steep gradient. The general appearance is a panorama of steep interstream spurs an rounded peaJes. Flat inland is confined to the Charlotte Amalie area and a few small alluvial-filled \ embayments. The only variation in the general » topography is in the upper valley of Turpentine Run in : eastern St. Thomas. The valley has relatively gentle topography consisting of rolling hills in a basin surrounded by steep slopes and sharp ridges. The Tutu Formation, the youngest rock exposed on St. Thomas is composed almost entirely of angular debris derived from the Louisenhoj Formation (an older volcanic formation) and minor limestone debris from thin limestone deposited contemporaneously with the Tutu Formation. The rocks were subsequently tilted to form a northward- dipping homocline. Dips range from 15 to 90 degrees and average about 50 degrees. Locally the formations are overturned. The permeable zones that these rocks once may have had after deposition have been destroyed by metamorphism or by deposition of minerals in pore spaces. Groundwater movement is now limited to openings along joints and x fault zones. The homoclinal structure is cut by sets of faults trending N 45*11, M 55'B and north. Three well-defined joint sets parallel each of the major fault directions. The valleys of the island have similar trends and are apparently the result of selective erosion of rock weakened by faulting and jointing. Prime zones of groundwater availability, therefore, follow the valleys. Small alluvial deposits ranging from Pleistocene to Bolocene in age, lie in the valley of Turpentine Run in east-central St. Thomas and the larger coastal embayments. The alluvium of Turpentine Run lies in a narrow band seldom more than 200 feet in width along the stream. Maximum thickness of the alluvium is about 40 feet. Most of the alluvium, which is composed of silt, fine sand, and clay and contains discontinuous beds of sand and gravel 2 to 3 feet thick; lies in the Mt. Zion-Tutu area of the upper basin and in the narrow valley from Mariendal to Mangrove Lagoon in the lower basin. The alluvium extends out under the lagoon near the mouth of Turpentine Run. Although composed predominately of fine-grained material, the alluvium readily infiltrates TUT 002 012V 2.3 streamflov when the groundwater level is below the base of the stream. As such, the alluvium forms a readily rechargeable aquifer, although it is of small extent and yield. SOB* coastal embayments headed by intermittant streams contain small deposits of alluvium similar to that of Turpentine Run. Maximum thickness of these deposits is estimated to be 50 feet, and their areal extent seldom is greater than a few acres (an exception being the Long Bay and Airport areas near Charlotte Amalie) . Near the sea, the alluvium interfingers with calcareous sand and at times contains lenses of mangrove swamp deposits. Therefore, the deposits are of minor significance as sources of water".*1' "Rain is the only natural source of fresh water to replenish the water resources of the island. Rainfa] is seasonal, with a rainy season in late summer and early fall and a secondary wet season usually in May. Nearly half the rain falls during August -November. RaJ.ns exceeding 1 inch in 24 hogry cop*. «*r in hour period about nnee every 2 years in large storms. xnese rains can occur In any month , but are more like during the hurricane season (August-November) . About 50_jgercent of the time a"*w*i rainfall j« between 40 Sjbincfies; Less than 10 percent of the time annual rainfall is under 35 inches, which usually means a major deficiency during the normal wet season and drought. The cumulative departure from average and the 10-year running average of rainfall shows that at this time of writing (1967) the island may be entering a period of deficient rainfall. With the exception of a few years in the late 1940's and early 1950's, rainfall in the past 30 years has been below average. There has been a long-term decline of about 10 inches in annual rainfall since the peak of the surplus rainfall period in the early 1930's. The most severe droughts on record occcurred in 1964 and 1967, when only 27 and 24 inches of rain fell, respectively. Areal distribution of long-term rainfall, is controlled by topography and the prevailing easterly to northeasterly winds. However, individual storms may or may not show the effects of orographic control or prevailing winds and the areal distribution of the storms can be very irregular".*1' See Figure 2-3, page 10, for average yearly rainfall. 2.4 Sampling Results The Tutu veil site has been sampled repeatedly over the last ten months and found to contain definite contamination. The initial assessment was conducted in July through September of 1987. Subsequent sampling and analysis has proceeded on a monthly basis. The initial assessment considered 26 wells and approximately 50 cisterns. Of these veils and cisterns; 24 veils and 5 cisterns vere found to be contaminated. The 5 cisterns vere cleaned and disinfected by the ERGS contractor. Subsequent monitoring has been considered for the 24 veils that shoved some type of contamination. Table 2-1 pg. 12, lists the veils included in the current sampling program. Tables 2-2 and 2-3 , pages 13-16, shov the volatile organic analysis results of the contaminated veils and give the highest concentration of organic contamination found during the last six months. The sampling, and most of the preliminary Photovac portable GC screening, vas conducted by the U.S. EPA Region II TAT. Drinking vater laboratories have performed formal analyses to verify the photovac screening results and to cover the entire spectrum of possible hazardous contaminants. Although, the concentration of these contaminants fluctuates monthly, it is notevorthy that the major contaminants have been 1,2-trans-dichloroethylene (DCE), trichloroethylene (TCE), tetrachloroethylene (PCE), toluene (TOL), benzene (BEN), tertbutyl methyl ether (TBME) and various metals. Their high concentration in four veils; Tillet, Harvey, Smith and Steele has been evident from the initial assessment. These veils shov concentrations of volatile organic* (VO) in excess of 1,000 ppb. The major and most consistent contaminant appears to be PCE. The Tillet veil has also shovn very high DCE and BEN contamination. Four other veils; Francois, Mathias, Four Winds, and Elgin; vere confirmed to have >50 ppb VOCs. The last confirmation analysis conducted during October 1987, included the entire Hazardous Substance List (HSL), (consisting of approximately 150 chemicals). At that time, significant levels of TBME up to 470 ppb, and methylene chloride up to 120,000 ppb vere detected. Some samples have also shovn traces of vinyl chloride, chloroform, 1,1,1-trichloroethane, bromodichloroethane, xylene, and ethylbenzene. Finally, the HSL analysis also shoved the presence of 11 TABLE 2-1 CURRENT WELL MONITORING PROGRAM AND CLASSIFICATION AT TUTU WELL SITE WELL NAME CLASSIFICATION OPEN/CLOSED 1. Dede Public Open 2. Steele Private Closed 3. Elgin II Conercial Closed Elgin 12 Conercial Closed Elgin 13 Conercial Closed 4. Four Winds Conercial Closed 5. Smith Private Closed 6. Bryan Conercial Open 7. Harvey Private Closed 8. Tillet Conercial Closed 9. Harthman Estate Private Closed 10. Devcon fl Conercial Open Oevcon 13 Conercial Open 11. VTHA II Institutional Closed VTHA 13 Institutional Closed 12. Dench Commercial Pump/No Power 13. Ramsay Private Open 14. Harthman Crusher Commercial Closed 15. Alpha Leonard Private Open 16. Francois Private Open 17. Demitris Commercial Open 18. Rodriguez Auto Private Open 19. Harthman Bakery Conercial _ Closed 20. Mathias Private Open Definition of Classifications Private: Wells which serve one or two houses. Commercial: Wells that are used to yield water for sale. Institutional: Wells owned and operated by a non-profit institution or governmental agency. Public: Wells that are for public use. 12 TUT REFERENCE NO. 7 S-728 101:1501 FISH AND WILDLIFE SERVICE LIST OF ENDANGERED AND THREATENED WILDLIFE AND PLANTS (50 CFR 17.11, 17.12; As shown in Code of Federal Regulations, Volume 50. Revised as of October 1, 1983; 48 FR 46057, October 11, 1983; 48 FR 46331, 46336. 46337, 46341, October 12,1983; 48 FR 49248, October 25, 1983; 48 FR 52742, 52746, November 22, 1983; 49 FR 1058, January 9, 1984; 49 FR 1994, January 17, 1984; 49 FR 2783, 2786, January 23, 1984; 49 FR 6102, February 17, 1984; 49 FR 7334, February 28, 1984; 49 FR 7394, 7397, February 29, 1984; 49 FR 10525, March 20. 1984; 49 FR 14356, April 11, 1984; 49 FR 21058, May 18, 1984; 49 FR 22329, 22334. May 29, 1984; 49 FR 27514, July 5, 1984; 49 FR 28565, July 13, 1984; 49 FR 29234. 29237, July 19, 1984; 49 FR 30201, July 27,1984; 49 FR 31420, August 7,1984; 49 FR 33885, 33892, August 27, 1984; 49 FR 34494, 34500, 34504, 34510, August 31, 1984; 49 FR 35954, September 13, 1984; 49 FR 40038, October 12, 1984; 49 FR 43069. October 26,1984; 49 FR 43968, November 1, 1984; 49 FR 44756, November 9, 1984; 49 FR 45163, November 15, 1984; 49 FR 47400, December 4, 1984; 50 FR 1056, January 9, 1985) t Title- 90—Wildlife and FWMrim CHAPTER I—-UNITED STATES FISH AND WILDLIFE SERVICE. DEPARTMENT OF THE INTERIOR SUKHAPTtR •—TAKIN«J. POSSESSION. TRANS- PORTATION. SALE. PURCHASE. BARTER. EX- PORTATION. AND IMPORTATION OF WILD LIFE PART 17—ENDANGERED AND THREATENED WILDLIFE AND PLANTS Arthartty: Pub. L. 93-205. 87 Sut. S84; Pub. L. 94-359. 90 Sut. 911; Pub. L. 95- 632. 92 Sut. 3751; Pub. L. 96-159. 93 Sut. 1225; Pub. L. 97-304. 96 Sut. 1411 (16U.S.C. 1531 eneq.) [Amended by 49 FR 21058, May 18. 1984: 49 FR 22329. 22334, May 29, 1984; 49 FR 27514. July 5. 1984. 49 FR 28565. July 13, 1984; 49 FR 29234. 29237. July 19. 1984; 49 FR 30201, July 27. 1984; 49 FR 31420, August 7, 1984. 49 FR 33885. 33892. August 27. 1984; 49 FR 34494. 34500. 34504. 34510. August 31, 1984; 49 FR 35954. September 13. 1984: 49 FR 43968. November 1. 1984; 49 FR 44756, November 9. 1984. 49 FR 45163, Novem- ber 15. 1984: 49 FR 47400. December 4, 1984; 50 FR 1056. Jaavcry 9, 1985] $17.11 wiUUft. (a) The list in this section conuins the names of all species of wildlife which have been determined by the Services to be Endangered or Threatened. It also con- tains the names of species of wildlife treat- ed as Endangered or Threatened because they are sufficiently similar in appearance to Endangered or Threatened species (see 517 50 ei seq.) (b) The columns entitled "Common Name." "Scientific Name." and "Verte- brate Population Where Endangered or Threatened" define the species of wildlife within the meaning of the Act. Thus, dif- ferently classified geographic populations of the same vertebrate subspecies or spe- cies shall be identified by their differing geographic boundaries, even though the other two columns are identical. The term "Entire" means that all populations throughout the present range of a verte- brate species are listed. Although common names are included, they cannot be relied upon for identification of any specimen, since they may vary greatly in local usage. The Services shall use the most recently accepted scientific name. In cases in which confusion might arise, a synonym(s) will be provided in oarentheses. The Ser- vices shall rely to the extent practicable on the International Code of Zoological Nomenclature. <c) In the "Sums" column the follow- ing symbols are used: "E" for Endan- gered. "T" for Threatened, and "E (orT) (S/A)" for similarity of appearance species. (d) The other dau in the list are non- regulatory in nature and are provided for the information of the reader. In the annu- al revision and compilation of this Title, the following information may be amend- ed without public notice: the spelling of species' names, historical range, footnotes, references to ceruin other applicable por- tions of this Title, synonyms, and more current names. In any of these revised entries, neither the species, as defined in paragraph (b) of this section, nor its sutus may be changed without following the procedures of Part 424 of this Title. (e) The "Historic Range" indicates the known general distribution of the species or subspecies as reported in the current scientific literature. The present distribu- tion may be greatly reduced from this historic range. This column does not imply any limitation on the application of the prohibitions in the Act or implementing rules. Such prohibitions apply to all indi- viduals of the species, wherever found. (0(1) A footnote to the Federal Regis- ter publication! s) listing or reclassifying a species is indicated under the column "When Listed." Footnote numbers to Sil7.11 and 17.12 are in the same nu- merical sequence, since plants and animals may be listed in the same Federal Register document. That document, at least since 1973. includes a statement indicating the basis for the listing, as well as the effective date(s) of said listing. (2) The "Special Rules" and "Critical Habitat" columns provide a cross refer- ence to other sections in Parts 17, 222. 226, or 227. The "Special Rules" column will also be used to cite the special rules that describe experimental populations and determine if they are essential or nonessential. Separate listing will be made for expenmenul populations, and the sutus column will include the following symbols: "XE" for an essential experimental population and "XN" for a nonessential expenmenul population. The term "NA" (not applica- ble) appearing in either of these t»o col- umns indicates tfcat there are no special rules and/or Critical Habitat for that par- ticular species. However, all other appro- priate rules in Parts 17. 217-227. and 402 still apply to that species In addition, there may be other rules in this Title that relate to such wildlife, e.g.. port-of-entrv requirements. It is not intended that tne references in the "Special Rules" column [S«c. 17.11(1X2)) Pubun«d ey THE BUREAU OF NATIONAL AFFAIRS. INC.. Washington, o c. 20037 29 ENDANGERED WILDLIFE S-713 101:1511 Alligator. American -_.. Alligator miuiuippie . .do. , Mnimn »> a FR AUM. Ocuaii 12. IM)| US.A (FL«nd (XOA. SCI . USA (LA. TK) E •' 11 il.i , »C in ' JO 47 I SO ill ;• T(S/A| ,. 4: I 51 i : »C '•• • incapacity ' TIS/A) • .- nAaroar (ound ' «< in NA ' I7*aai A*CUO> CMrm* BOO.MW* . .... Caa PVC-K Mce Boa. Mem* Wand [-0 '; AH-^ijr «gn«M* 1 CIM . ...... .... .. : uS.A <PU»IC *>JB ~~'*ft *»nd) VWMM nanjMut ! two** «ar/vfua ..... . ?irt»-» «fe.ucannMi ———————————._ £«•»•<« »r»"K yytfl I •!•! ll•»••,» • tlMfleix.'ui new . tacai* ' iVocoaio. A!.«ar •.. CraeodM. Amanun | USA C-^vTO fls-3> | 30 . . ...... ... i inoan Ocvan ! Mdwi Ocaor. Uiu-n-.-i . i, i; S me Bman v>;{x inanoi.. u i ... ac ... - ... do . ... . I ..==. A. « ........| 90... .1 K ..... ; CneetHM c*\+*J»n» . ' CafMnmutj*' Cmc&dM. Co>v; OMar docadM. Cuan CrocjMW MOMNXI . . OocaJn. i«igg.r......... CraeaM. Nia .. ....... OooodW. Onnpco Cneyttr OCOV» lOMMMrl ......; o ' f>r«x*^*a ., C-oaxs*« | OjpaMa i»»iini» 1 C'i«u<«*« ftntui ' Mcuco ........._.... ... ... ... .... . i ..do . ' w*atAirca........... .. . . . ' ao • *••«••" »K oai*» A»x> . ' 97 ..' (JSA. |Fu M««u. Soo* *_-,*•_*. C*n- i ..do . I »« Amanca, i*ta.^ i | ... v Lama ............. .. - ... .. ' .. «o . .. -1 Cof»> *<>*> tmnff.... ..... . . . . . . . .....ao ....; Ct*a.._..._............................. . . . . . . ..da. . ,i .... as . ... | _.. no .....' ..... O3 ! So>* A-^nt. 0-voca ^-var law......_..! ... ..do . 1 naa. ^umnn. nan »».<v«J»«n .., **ca. •*i... , f 'j 'oiv^a 00 J4--IJ iOlir. «d«n Ucoor, IMutrjui ....... . USA (Pum* Moo) .............. 00 do iguana. ATani Cm, ta>» A AnafUa irs^id ._.. \Ctune* do.. w»: ineia*. 6<-. t^aUtAWVM MM I D iS"r.^ir.i:'.:.zJ z» ::...z..zz...::: bur* IAI» ; ;c>«»w< TV)M>.. .... .. . ...... ... ...J _..._.........___.._.._! wwai i • _............. .... ..........J do ii a*a.. .......... .| u.SA (C UIX Puarta Mea: Mana Kanai WaM mat Tn*a and Cawca .. Jo . :.1.i2:- .! ... oo . I ... ao ' ......do • Cam* [Added b\ 49 FR 7397. February 29. I984J E E i t , f E E ! E E C E C C e E E E i E E E F ; E : £ , T T i T 1 T 1 is i7-.S(.. 3 KA 33 ! I - 55,.-, ' ; >>i* i M NA 1 NA is ' 1§ 1 15 3 0* IS S »? i i* : it 21 3 ! IS ' ST ' 3. ?f i 3 1 U4 • 3 ! 124 ' \K . !l» ; 1?9 ' 3 1 «Jf i 1» , 1 13* i NA : '.A ' NA , NA i SA NA '-* NA 1 NA N* NA ' NA ' NA SA N» N4 HA NA ) NA NA NA 1» !Jt NA 33 "MCI' >Zt NA : !Z» NA N»- Ui : [Added by 49 FR 7397, February 29. 1984) s» NA N» »A N* NA N* M N« NA K* hA (•« NA NA NA NA NA NA NA NA NA NA KA NA NA NA NA f.A NA NA NA NA NA NA NA NA NA NA NA NA 10-12-64 PuMthM Dy THE BUREAU OF NATIONAL AFFAIRS. INC.. WMlungton. 0 C REFERENCE NO. 8 MUS CORPORATION TELECONNOTE CONTROL NO: DATE: TIME OISTHIIUTION: 0)0 7 S*to i •ETWCEN: OF: PMONE: AND: INUSI OMCUSSION: OLc u T-l-c r \ ACTION ITUM: I REFERENCE NO. 9 EPA REGION II SCANNING TRACKING SHEET DOC ID #64413 DOC TITLE/SUBJECT: TUTU WELLS SUPERFUND SITE TABLE-1 DESCRIPTION OF WELLS AND SEPTEMBER 11, 1987 WATER-LEVEL MEASUREMENTS IN TURPENTINE RUN BASIN, ST. THOMAS, U.S. VIRGIN ISLANDS 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 REFERENCE NO. 10 Uncontrolled Hazardous Waste Site System A Users Manual (HW-10) Originally Published in the July 16,1982, Federal Register United States Environmental Protection Agency 1984 TA1LI 2 FII1BUBII.ITT OF GEOLOGIC NATKUAU* Approxlaata taaja of Aaaigaed Typa of tut •rial______________Hydraulic Conductivity_____Valua Clay, coapact till, stela; uafracturad <10~7 ca/aac 0 aataaorakic aad igaeoua rock* Silt, loaaa, ailty clays, cilty 10~3 - 10~7 ca/aac 1 loaaa, clay loaaa; laaa paiaaabla liaaatoaa, doloaltaa, aad aaadatoaa; aodatataly paaaabla till fine aaad aad «ilty aaad; aaady 10~3 - 10~5 ca/aac loaaa; loaay aaada; aoaacataly paxaaabla liaaatoaa, doloaitaa, aad aaadatoaa (no karat); aodazataly fraetaiad tgaaoua aad aataaorpUe racka, aoaa coaraa till Crawl, aaad; hl«Bly fraeturad >10r ca/aac igaaoua aad aataaorphic rocka; paraaabla baaalt aad lama; karat liaaatoaa aad doloaita •Darivad froa: Davla, S. •.. Baroaity aad ParaaabAlity of fctural Hatariala ia Floir-Tbrootk Poroua Madia. t.J.M. DaWaat ad., aeadaaic Praaa. Maw York, 1969 Fraaaa, l.A. aad J.A. Cherry, CreaaaHatar. Praatica-lall, lac., tew York, 1979 15 REFERENCE NO. 11 The Geological Society of America Memoir 98 CARIBBEAN GEOLOGICAL INVESTIGATIONS By H. H. Hen, Editor Dtft. Otology, Princtton Unotrtity, Primuton, Note Jtrsty CarlO. Bowin Woods Hob Oetanogrtfkie Institution, Woods Holt, Mossatkusttts Thomaj W. Donnelly Dtft. Otology, Rut Umotrtity, Houston, Ttxas John T. Whetten Dtft. Gtolofy and Octanagraplty, Umotrsity of Washington, Stattit, Washington E. R. Oxburgh Dipt. Otology and Mintralogy, Oxford Unutrrity, Oxford, England 1966 it *'* f, 94 CARIBBEAN GEOLOGICAL INVESTIGATIONS the final base map. have good shore-line detail. Mapping on St. John was done on 1:20.000 enlargements of the 1:40.000 U.S. Coast and Geodetic Survey map. Aerial photographs of approximately 1:30.000 scale were use- ful for some structural interpretations. Exposures along the shore lines ranged in quality from excellent to very poor. Those inland, except in recent road cuts, were almost invariably very poor. The best ou|HMjtiMttMlk St. Thomas and St. John are sleep cliffs, which are in P'^^MBHliP '"verse. More sheltered shore lines are easily walked, but rw^flMMWAere are much poorer. laboratory iiwcsiigaiMMHPHMlmilMwdy of several hundred thin sections, X ray diffraction examination of rock samples and mineral separates, about 300 partial chemical analyses, and numerous mineral determinations by optical examination of crushed samples. About a doien feldspars were determined by measurement of index of refraction of grains oriented on the universal stage, according to the method of Smith (I960). Approximately 100 additional plagioclase samples were determined by measurements of indices of refraction of unorieiued grains. An extensive optical study of the feldspars, completed after this manuscript was first submitted, has been published elsewhere (Donnclly. IOCS). Pyroxenei were determined by meas- urement of n, and 2V, according to the method of Hess (19-19). SUMMARY OF STRATIGRAPHY OF ST. THOMAS AND ST. JOHN The rock units of St. Thomas and St. John (Fig. 2) can be divided into three major groups: the Water Island Formation, which consists of kera- tophyres and spilites; the Virgin Island Group, which consists of andcsilic pyroclastic rocks and sediments; and one or more diorilic plutons. The \Vater Island Formation possibly is late Lower Cretaceous. The Virgin Island Croup is probably Albian (although the Hans Lollik Formation could be Eocene), and the diorites are early Tertiary. The oldest rocks in the Virgin Islands are the keratophyres and spilites of the Water Island Formation. These volcanic rocks are predominantly flows and (low breccias, but keratophyric py roc last ic rocks are widespread. A few of the fine grained tuffaceous beds conuin well-preserved Radiolaria of undetermined age. Noteworthy in the Water Island Formation is the ab- sence of terrigenous sediments. This characteristic, together with their ap- parently igneous mineralogy, has led the writer to the conclusion that they are probably volcanic rocks which were extruded on a relatively level ocean floor, prior to the existence of a trench or island platform. In contrast to the postulated abyssal environment for the Water bland volcanic rocks, most of the overlying pyroclastic rocks of the Virgin Island Croup were extruded suhacrially. Both the volcanic and sedimentary locks exhibit slump structures, and some megabieccias contain limestone blocks up to 100 feet long. The bulk of the sedimentary lorks in the Viigin Island T. W. UONNELLV—ST. THOMAS ANU SI . JOHN, |l. S VIKC.IN 1*1 AM)> 'J'l Cioup are co.use wackes consisting almost eniiicly of slightly utJilii.ic.cl debris derived from the andesilic pyiorljstic rocks The deposition ol ihii group may have .icrninpanied the formation of (he initial isl.ind plaifniiii and trench. HANS LOLLIK FORMATION ("0.000 feel * I AUSlTE-ANOCSlTE e«lCCU tut TUFF Ucwr ,nt lo»tr caitlac'l n<"! Mil TUTU FORMATION (6000 f e e l ' ) TuFfACEOUS VnACKE Includii mar lh« bait lti« Cokl Point Megobreccio lilhofocies N.ar if.. ia» i> ir.« Congo Cay Limtslont Mtmber (200- 300 feel): COIHSLLT CRYSTIHINI LIMCSIONC. T»p •! fermonaii not ••ijoica' m U S iiljr OUTER BRASS LIMESTONE (200 - 60O ktl) PAArULLT SILIClFlCD, TUFFACCOUS. HAO.OIAHUN LlMCSrONE. LOUISENHOJ FORMATION (14,000 feet (W SI Thomas), 4000 leet (E Si Thomas). 7000 feel (W SI John)) AUCITC-ANDCSITE sntcci* M4 TUFF IBiUf tfACH >l CLEVEI Utar Iht »>«• it it» Cabes Point Conglomtrale lilhofocies Wlk »<bb«l •»< C*kblM (I W4IEM ISLAND FORMATION lllh«le«r UNCONFORMITY• WATER ISLAND FORMATION (15,000 fe«l+) KCmroPHTNE FLOWS. FLOW ancccus. wd TUFFS. •ilk JClLITt FLOWS and mln«r NAOlOLAMirES lulrydid br dikfi a»d plu|l ol KERATOPHTRE. 2. Slraiigrapliic ICilioti fni M. 'I IIOMI.II and Si. John. Vii^m Folding after deposition of die froindillcicnii.il vertical movement . ing from 15* to 'JO'. The associated of less than I mile. Although COMI.ICI emplacement of diorilic pinions arc Thomas and the southern third of St. Virgin Island Cioup louluil l.ngcly and pioilucnl .cvei.ige ilips of 11)', i.mg sliike slip faults h.itc lioiKonl.il oll><.is mclainoiphic cllccls icsiiliing from die extensive, the western luo thirds of Si John are essentially iiiiincijniorplio»e<l I 'JO CARIBBEAN GEOLOGICAL INVESTIGATIONS WATER ISLAND FORMATION GENERAL STATEMENT The Water Island Formation of possible late Lower Cretaceous age consists almost entirely of keraiophyre. spilite, and radiolarian lull. The ex jx>scd thickness of this formation u 15.000 feel, based on project ion of (he highest and lowest hoii&avgu*.,A reasonable correction for Icniiculariiy might lower the line thkliijp|f *• wposed section to 8000 or 10.000 feet. IVatcr Island, in the haiUt of <2foffcMie Amalie. St. Thomas, has been selected as ihe tyjie locality because ol the great variety of rock types there ami the general excellence of exposures, although excellent exposures crop oiii extensively along the south shores' of St. Thomas and St. John. "Keratopl>)rc", as used here, is an extrusive or hypabyssal intrusive vol- canic rock consisting prodiminantly of albiie and quariz. with cliloritc. micaceous mineials, and iron oxides. Nearly all of the Virgin Islands kerato ph)re| contain considerable free quariz, commonly as conspicuous phcno crysis. Those with cpiartz plienocrysts could be called "quartz keraio- ph>rc" bui many aphaniiic rocks here called "keiatophyrc" are chemically identical to the so called "quartz keratophyres" and the simplest term is pic- ferred for all these rocks. A striking feature of keraiophyrcs is the absence of phenocrysis (or pseudooiorphs) of pyroxene, aniphibole. and mica. Keralo plijric Oows and crysial tuffs are sodic. with a very low potassium contciii. but some apparently vitric tuffs are slightly more potassic. Keraiophpc in- trusive rocks have a higher potassium content an ' commonly contain sec- ondary monoclinic K feldspar. "Spilite" is a greenish seemingly altered extrusive or hypabyssal intrusive loci, consisting of chlorite and albiie, with variable amounts of epidoic. prehnite. and cakite, Fresh phenocrysis of clinopyroxene are generally proem; amphibole and olivine were not seen in the Virgin Islands spilitcs. Amvgdulcs arc abundant and commonly contain most of the calcium con- tent of the rocks as epidote. calcite. or prehnite. with quarti and chloiiie. These spiliics contain about the same amount of Na,O as the atigiic aiidcsites of ihc Louiscnjoj Formation, and about 0.5 per cent more than Virgin Islands diabase dikes. Included with the spilitct here is a partially albiiiied augile andesite which occurs near the top of the formation. The name spilite hat been applied in the past 10 many diverse rock ty|>cs. some of which may be low-grade regionally metamorphosed andesites or basalts. Other spilitcs appear 10 have been unusually hydrous nufic intru- sive rocks, and many ate deuterically altered basalts or andesites. However, iheie is an impressive body of evidence that many so called spilites. notably certain Oidovkian, Devonian, and Cretaceous geosynclinal spiliies, have characteristics which can be best explained by assuming an essentially mag- ma tic origin for these rocks. It is to this laller group of rocks that the Water Island Formation spiliies belong. 1. \V. l>l>.V\ll L» — M. IIIOMt) AMI Jl Jl'II.N. I' .1 \IK|.|N I.I IMP, •!, Such spiliies may be thought of as locks which h.ive funned by alhm/.i lion of andesiies. However, this process is believed to occur dining a late stage in the solidification of a hydrous mafic magma and is not caused by later metamorphism. Given a ceriain combination of physical and cliciiin.il conditions, spiliiiiation of mafic extrusive rocks is inevitable. Hence the term, applied in an admittedly restrictive genetic (hence subjective) seme, is a useful one and should be retained. 'I lie author admits that lowgi.i.l. mcinmoipliism may obliterate the mincialogical criteria neccssaiy fur tin recognition of spilitu.ilion. Chemical anal)sis ci( a l.n^e and caicfully selected suite of specimens might icve.il whether or not the IMCI.IIIIOI j.bu rocks in question had been originally spilui/cd. bin such anal)iis might alin fail to do so, and the term should be applied with i.ne KI siuh lock build Kl KA IDI'IU HtS l iln lillriiiliiiliny iliili'iiicnl. Kei.no|ib)ie iniiljiii^i .ilioul funi li \ValcT Island l-di ni.nioii Most Leialopbyic occin* a> llmvs ami llou hieni.ii. with minor tnfls. bulb ciysl.illinc and viliii (the l.illti .iln.ijb ilet in iliecl) .mil. rarely, volcanic biecci.n Kei.ilophyiic inlriisixe loiLi aie not HIM .minion, they oicur .is both dikes anil plug), commonly with vei y we II <levcl<>|Hil columnar jointing. Kci.ilnjihyi ic fluus .11 L gcun.clly Km of feel in lliuLiioj I c \v iliul lluu^ are completely exposed from lop lo base; those which aic well exposed aie striking only for their lextnral uniforinity. Haling ami chilling phcnonien.i aic absent. |-'low bamling. imi.illy somexvh.il contoitcil, is seen hxally (PI X fig. I). Comae is between (low units aic commonly dillicnlt to identify a> such, and altitudes of the flows aic not always easily astcil.iiued One thicL Lcralophyic flow neai the base of the section, on Ram lle.nl. St. John, shows gogd field and peuographic evidence of veitical diffcienda lion The flow is about IG5 feel (hid, and near the center i> icihlislt giay. grading logieciiish gray downward and iipw.nd. I'etiogi.iphic dilfcicticcs will be discussed later. The color change observed in the held would appeal in bo lelaled to a dilfeienli.il drgice of oxidation of iion within the flou which is probably lelaled lo iclative loiicenlr.ilion o( volniles in the lloiv center during cooling. Kcraiophyrc flow bieuias, oiciiriing as disciete beds, aie piobably mou common ihan flows in ihe Leraiophyie sequence bin aie difficult to dis- tinguish fiom Hows. 'Ihe maliix of the How breccias can fieipiently l» tlislingiiishcd fiom the fragments only by careful sciuiiny of the ontiiop; ihe patina of we.ilhciing which covers most kcratophyies effectively obscincs the fine details ncccssaiy to lecognile these rocks. Fragments in flmv brctcias aie subangnlai to subionnded. The matrix is almost identical 10 the fiag menis in polished section; however, the matrix wc.ulieis moie ia|<iilly. ami in outcrop a flow breccia will appear i (Higher in gioss uxinie than a flow. A few flow breccias consist of both Lerlophyrc and spilitc fragmenis. One —( y8 CARIBBEAN GEOLOGICAL INVtSTICATIONS such occurrence (sample GSJ-2. near the west end of Great St. James Island) is a 100 foot iliick bed of keraiophyre and spilile rubble with a few lime- stone fragments set in an apparently igneous matrix. The minor rccrysialliza- lion of the limestone suggest! a low temperature of extrusion. No conglomer- ates were identified within the Water Island Formation, although many flow breccias have rounded at wtUfi angular fragments and. when weathered, resemble conglomerate*. jAUHKilfc* (wmple ST-274. Lisenlund, Si. Thomas) would undoubie^HvflPtil a conglomerate by most field geol- ogists, but unweathered iptOMM found a short distance eastward along the su ilc show the igneous matrix very clearly. Tulfs and volcanic breccias form minor but distinct uniis in the forma- tion. Tuffs (grain sue leu than 32 mm) are much more common than breccias and occur as beds only I or 2 feet in thickness. None of the lull units could be demonstrated to have a horizontal extent greater than about half a mile. Grading is visible in the luff beds, although this grading is commonly interrupted by ilia si ems representing the action of water currents on the sea bottom. Slump structures, generally in the form of com or ted betiding, arc uncommon. Many luff beds are silicificd. although the original py roc LSI ic gioundmass is recognizable in thin section. Apparently the origin- ally vitric groundmass of many tuffs has altered to fine-grained mica minerals; muico\itc is the most widespread, and celadoniie and stilpnomelane have been recogni/ed. One of the best exposures of a keraiophyre breccia is on the cast shoic of Lameshur Bay. St. John (sample SJ-7). Here a bed several tens of feel thick consists of angular fragments of keraiophyre a few mm to 5 cm in a reddish, hcmatiiic matrix (PI. 4, fig. 4). The hematitic matrix contrasts with the more neutral colors of most other keraiophyre flows and luffs in which hematite is generally subordinate to magnetite. Dikes and shallow plutons of keraiophyre occur throughout the fiuin.i- lion, but are most conspicuous in the hills southwest of Charlotte Amalic. St. Thomas (llaypiece Hill. Grambokola Hill. Sara Hill. Cabriiaberg). in the vicinity of Nazareth Day. St. Thomas, and in the vicinity of Hodman and Mi. Zion, St. Thomas. (Mt Zion itself, however, is underlain by another type of intrusive lock.) These bodies commonly exhibit columnar jointing |>upcndicular to the cooling surface, and examination of the joints pro- vides a means of reconstructing the shape of the intrusive body. The hills around the Submarine Base on Si. Thomas (Cabritabcig. Giani- bokola, Ha>piece, and Sara hills) are underlain by one or two intrusive bodies known collectively at the Submarine Bate Pluion. The accompanying map and sections (Fig. 3) show that the form of the intrusive body is irregular. The pattern of joints around llaypiece Hill strongly suggests the presence of an intrusive funnel beneath this hill. The joint pattern bcncuth eastern Sara Hill, on ihe other hand, would appear to suggest lhai the floor of the intrusive body is siibhorizoiiial, irregular, and shallowly dipping here. The intrusive extrusive contact near a probable vent at the southern end of 1. W. UONNLI I.V — II. IIIOMAS ANU SI. JOHN. II i VIKI.IN !•>! -»NI)1 '.)'• Cr-iinhokola Hill is inodeuu-ly sleep. On Cal>iil.il>rig Hill ilir column.n joints arc nc.uly lioii/onul or sh.illoul) dipping iiiu.inl ilic iiinilnin c-iul of the intrusive body, bin are nc.nl) venic.il j|>|>io\iin.iul) 300 li-c-t muili of the southern contact An outcrop of exmisiie rink, cvidunl) omniin^ FICUIC J. Map anil (ion iciiiom ol'ihc. SiiLinjiinc H IH pluii I'liic I lor location. i. Si I IMMII..I K. I, i just underneath the inirnsivc bixly. un he ittn almiy die ilunc jnsi ionili of the Caribbean Hole). Hue the inumivc body was probably fed through a sleep conduit al its southern end, and spread nonliwanl .is j longlil) conformable sheet. Ii i> not known whether or not ihis inirn^ivc Ixxlj connects with the othei one at shallow depth. . The occurrence of intrusive keraiophyre in model jicly l.nge liodici i« ward the lop of the section may rcllcit a subtle upwaitl change in luholog): 114 CARIBBEAN GEOLOGICAL INVESTIGATIONS lure optics), and rare biotiiic mica and a mafic mineral which has altered completely 10 a hue grained, very red substance. Ibis could be either iddingsiie. bowlingite. or some other clay mineral or combination ol minerals. 1 he glass fragments have diffuse outlines and could be shards. In no case, however, has the degree oi preservation revealed the outlines uf the original glass liagniCMk TltC appearance ol these beds in thin sec- tion it veiy similar to tht ttiptpty 4evilrified lullaceous beds, [omul in ex- plosive rli)olilic suiles.< but tfcctr explosive origin is nut established by petiographic evidence. SIRAIIGMAPIIIC VARIATIONS The Water Island Koimaliou it icmarkably uniluiiu. consisting thiough out o( about one lilth spilitc and the remainder keratophyrc. 'I he lower por- tion ol the formation, seen best at Ram Head, St. John, and on Cicat St. James Island, consists doiuinanily ol thick kciatophyre Hows with inter- calated spilites. Breccias and pyioclasiic rocks are minor and form only very thin units with a limited later.il extent. The upper portion of the for- mation, seen best in the vicinity oi Charlotte A ma lie, St. Thomas, and on Water Island itself dilleis principally in the greater percentage ol pyroclastic units. Aionnd the intiusive bodies of llaypiece Hill. Orambokola Hill, and Cabiiubeig. the foimaiion is dominantly pyroclaslic, with only a few thin kcratophjric flows. On Flag Hill, straligiaphically slightly lower than these p)ioclastic tocks, a strikingly thick pyroclastic unit is intercalated in a dominant!) flow sequence. No mincralogical distinctions between the lower and upper pot lions of the formation can be seen except that near the lop of the formation theie is one occurrence of oligoclase and albile with high-temperature optics, and theie are three occurrences of albite with optics which deviate significantly from the low-temperature state and which have been called quasi low icntpci jtnre optics (Donnelly, IOCS). ENVIRONMENT The most striking (eatuie of the Water Island Formation is the complete absence ol terrigenous sediment: the entire exposed thickness consists of volcanic rocks only slightly reworked locally by water. The second impor- tant feature of this unit is that most of the volcanic rocks, except for the uppermost 5 per cent of the formation, are flows. The pyioclasiic rocks themselves consist entirely of relatively eqnanl, angular fragments, and shards or pumiceous fragments are not seen. The quiescent eruption of appaienily hydialed magmas must indicate that these magmas weie erupted under a confining pressure of superincumbent sea water approxi- mately equivalent to that of the deep sea bottom, which is sutlicicnl to pic vent the explosive expansion of a maginalic gas phase, llydrated magmas erupted in this environment will experience separation of volatile! if the T. W. DONNILLV—ST. THOMAS AND SI. JOHN, U. S VIKHIN 1st ANDS ||5 partial pressure of these volatile* exceeds that of the sea water (about 500 aim at 15,000 feel). The expansion of these volatiles. however, will be in the order of a few limes, not many thousand limes, ns would be the case if the magmas were erupted subaerially or in shallow water. Abyssal pyioclasiic rocks will not be formed by explosion but by relatively quiet expansion <>l volalilcs and sudden chilling by sea water. Dispeis.il of pyiotl.islii haginc-nit will probably be effected by slow moving bottom cur mm. in conxeciivt. currenis initialed by the release of he.it into the sea water. The absence <>l terrigenous sedimentary locks indicates that there were no cincigem islands which could have served as llic soiuic of wc.ilhcicd denims Slump structures or oilier evidences of deposition on slopes are picsciil Inn jie not abundant; in couiiasl, near the top of the formation ilieie .ire sevc-i.d soiling orcunences of evenly layered pyroclaslic keramphyir with no bed ding disliubanccs. Evidently (his formation accumulated not only in abys sal depths but also on i.tlher II n sea bottom. The appearance of slightly more explosive cinptives only ul ihe very top of the Foimaiion shows that the sea bottom may have been subsiding during the gi cater p.ni of the ac cumulation but that subsidence was not rapid enough to maintain .1 con slant water level at the eruptive (enter of the accumulated \uli.tnic deposit Alternatively, regional uplift near the end of Walci Island lime could ha\ been res|x>nsihle foi the appaicnl shallowing of watci VIRGIN ISLAND GROUP lOUIStNIIOJ KIIIM.MION Inlroiluiluiy sliilniicnt. Uni onfoimalily nu-il^ing ilii \\.un Island Foimaiion and cropping out on about hall the land .HIM of St. Thomas and Si. John is the l.ouisenhoj (Loo e' /an hoi) Foimaiion, n.iiiicd loi excellent ex|K»uics in road cms in llic vicinity of I iniiscnlioj, just noiili of Cli.ii loin Auialie, St. Thomas. [Tins iltick_sctjiieiKe is picdomiiunily aui;iie nndcsiif and varies in mode of deposition fiom pyroclaslic to epid.isiic. The inaxi mum appaienl thickness liavcisrd is about IJ.OOO leel. but a leasonahle correction for lentilnl.iiily mighl icdiue (his compnied thickness by a ihiid or more. Clete (IH7I) called this lock type "llhie llc.ifh and iliK iianic II.IN |>eisisted: all of the natives of tin Viigin Islands an- l.niiili.n uiil, ' |l|u< Itiich" or "Illuc Kit." The formation is thickest and almost enliiely pyiui l.istic (loull) ic-uoiked luff beds arc considcted essentially pyroclaslic) in westein Si Thomas. In eastern St. 'I homas (he Iniiiialion is nun h thiiiim (HUM) (cei) .mil is <om posed almosi eiiliiely of ut.nse ^lumpc'd and lewoiled p)iiul.isiii deluis. probably oii|;inalin<> liom a sm.dl subaeiial cone In WTSICIII Si |nlm the (ormalion is thicker (7(MIU feel iiiiniiiiiuii) and con>isls pn dumin.inily ol CO.use cone dc-biis. l-igmc- (i shows an inleipielalion of llu condiiions \\huli resulted in this disliibnlion of lock types and (hie knesses, l-.vidciuc lot ilu '— r 116 CARIDUEAN GEOLOGICAL INVES1ICATIONS T. W. DONNCI.I.r—ST. THOMAS AND ST. JOHN, II S VIRGIN ISI ANI'S I 17 postulated I'illsbury Sound eruptive center is based on the coaisencss of volcanic ejccia in nearby western St. John and eastern Si. Thomas, on die presence in Pillsbury Sound of a diorilic plutou, and on the necessity ol finding the nearest teasoiiable souice for the lithic (laments in the Louisen lioj Foini.itioii ol western St. Thomas. In western Si Thom.is (15 miles (KIIII the presumed eiupiivc ceniei) occasioiul angular Murks G iiuhcs in diam- eter are found in the ash bcd>, which themselves lange fioni fine iiilf to fragments about I inch long. The coarse cone dcbiis is most suiting in western Si John .mil t.niem St. Thomas. In ivcsic-iu Si. John -1 fool blocks of what mini have been subaeiially deposited ash fioin I lie slopes of the (ones aic found mixed in coaise conglomeratic beds. Near Mandal in eastern Si. Thomas l.ngc flag menll of what may have been j suhaerial andesiic- llnu- ate teen in birtii.is of debris eroded fiom the cone. Ai one totality fragments o( lluw up to 2 feet long rest in a matiix of finei ni.iteii.il Many of these liagmeiiis bioke apart just piioi to cessation of iraiispon, and their bioken oinlines can be matched in oulciop. This is the only piob.ible How m.ileiial ideiilified in diiv formation Ac the ly|>e locality the foimalion consists domin.intly of beds of (o.nse andesilir luff which, like most of die tnlf seen, was .ippaicnily w.uerlaid The beds are typically 0-12 feet thick and have f.iii grading u-iih the to.nscsi material (rarely coarser than about 3 imhes; a leu- Mocks i<> I foul) ne.n the base. These beds commonly show l.miin.ir slumping (I igs. 7. H) I he nio5i striking feaime of this slumping is the ;ihuml.ime of "pull .i|i.ui>" .md the frequent inieiiupiions and leveis.ils ol die gi.nliuv,' I In-, l.iiniii.n slumping is a veiy chaiacterisiic fe.iline of ihc I.ouiii nhoj I oiiu.iiion ami apparently fonned as follows: an :ibh fall was deposilcd miileiu jh i (I ig 7A) on a slope and developed fair grading, inicirupied («i.isioiull) by a luge angular block which depiesscd the bedding below it 1 he fine ash on top became cohesive more rapidly than did the roaiser ash below I lie le^ cohesive, coaiser material below slumped (Fig. 711), tarrying on ii and en- veloping within it fragments of (he more cohesive. Finn giained inalrii.il above. The (low was rarely rapid enough to become tuiIndent; the pulled apart beds have nearly all ict.iincd an oiieiiiation parallel 10 the bedding. During this process of slump ihc grading lost its original airangenient, and the coarsest maiciial is commonly found somewhat :ibo\e (he base of ihe unit. Additional evidence for dep<»ili«n on a slope is (lie nr.nl) uliii|iiii<im dump structure* seen in fine-giaiiied lulfs in the (oimaiion. Purely pyrocl.iilic beds are not always easily distinguished fiom lull b<d> which have slumped and fiom beds which have been moic or less reworked by water currents. Coaisci pyioclasiic rocks usii.illy exhibit die li.iguienl angularity, the uniformity of lilhologies, and the appairiidy igneous matrix which one associates with ash deposits, whereat finer ash In'ds re- semble volcanic wacke. Ihe over-all aspect of this formation suggests aeiul transport and subaqueous deposition of pjroclaslic debiis. TransputU- 120 CARIBBEAN GEOLOGICAL INVESTICATIONI Cain I'oint Conglomerate Inliolacid. Near the base of the formation in the vicinity of Ciui Bay. Si John, and Cabes Point. Pearson Gardens. and Bunker Hill. Si Thomas, conglomerates are inteibedded with andcsi- tic (i)roclastic and epiclastic locks. These conglomerates consist almost entirely of well-roiindetl ketatophyre cohbles and (nbbles derived from the underling Water Island Formation. At Cnu Hay. however, these conglom- erates are more or less mi*** **$ Midesitic debt is. suggesting that sub ac.ial erosion of (he cone*fj|*|j& *«l lhat of the umlcrlying keratopl.y.c bed* were sin.ulianeous. Ai &*X* Will the conglomerate is composed of well-rounded and laiily wcNwrlcd keratophyie and spilite robbles and pebbles These coiigloineiate beds appear to have been deposited in shallow water, and were not products of uibidily current dcjiosiiion. They aic well sorted, ate not graded, and have relatively little maim. Their presence indicates subaerial erosion, transpoit. and deposition of older roils dui ing early l.ouisenhoj time. ll'airr Island I ouiicnhoj contact. There are few places where the lunlaet between the Water Island and l.o.menhoj Formations is well exposed. In St. John there is one excellent exposure of the contact along the west shore of Monic U.iy. and there arc poor ex|K>surcs at Klein Bay. The cxposme on Mome Bay shows a conglomerate of the Loiiisenhoj overling a spiliie bed. The spiliie is quite fresh at the contact, and the over I)ing conglomerate contains a wide assortment of Water Island lilhologics iiu hiding, however, very few rocks identifiable with the underlying spiliie. At Calvary Bay. St. John, iheic is an exposnie of a conglomerate of the l.ouisenhoj Formation overlying keratophyre. On St. Thomas the contact itself is poorly exposed, but an extensive ex- posurc of Louisenhoj beds above the contact at the headlands between Brewer's Bay and the airport is of great interest because of the extent of apparently contemporaneous weathering displayed here. The Louisenhoj beds here consist dominantly of subaerially, varicolored andesilic ash inter bedded with conglomeratic Water Island detritus Some of the ash units are brick red and consist solely of albite. hematite, and a little illite (X-ray diffraction) The albiiiicd plagioclase phenocrysts evidently withstood the weathering almost perfectly, but ihc entire mafic part of the rock has been converted to oxide. Other units consist of varicolored fragments ranging from deep red to green, evidently reflecting differential susceptibility to weather- ing Still other units consist of greenish or grayish fragments in a uniformly puiplish matrix. The basal subaerially weathered unit is less than 100 feet thick and was found ai only this one locality. The color of the beds somewhat resembles that of the weathered hydrothermally altered rocks (discussed in a following section), but the latter grade into whitish unweaihcred rock within a few feet of the suiface and are mincralogically quite distinct. The exient of ihis weathering is completely unlike any recent weathering of any rock types in these islands and undoubtedly reflects weathering contempora- neous with original deposition. T. W. DONNK1.LY— ST. THOMAS AMI ST. JOHN. II S \ IRC.IN ISIAMiS I '.' I Another occurrence of conieinpoi.ineoui weathering is poor I) i-\pn>cd .11 Wintberg Hill, St. Thomas. "1 lie pool natural cspninm. ulmli .ne <>l lightly metamorphosed rock, weie oiiginally thought to lie <>l li)clioiliri mally alleied rock However, iccent (1 903) exc.ivalimis Im io.nl innsiinc linn revealed the originally weathered n.iinre cif these i«i Lv Mineralogy o\ mo/it fragment). 'I he piincipal iimui.iK loiunl in in.ilu fragments are plagioclase. clinop)io\ene. cliloiiie. anil |HMII|H ll)iic, anil aliu matrix and opaque minerals. HANS ————————— TUTU O tOLLIK fM FM OUTER 0 I ° 0 ° I 80 r x JJ Mony _/j Somplcs LOUISCNHO Spililittd Aug WATER ISl O BRASS LS. O dD • 0 » J FM c - - tie Andesile AND FM O Mony O ~) Somples -O o 0 0 An, An20 An 40 "60 "80 An100 O LT ond OUT (Oonnelly. I9C3) optics • HT optics 1'icuu 10. Coiiipoiiiioiii of plJfioclJU) aiiJiigril accouling lo nurigupliii |>ixiii»ii FLACIOCLASE: Most phenocrysts.of the l.ouisenhoj andesitrs arc labiailoiiic. about An,» (Fig. 10). Near the base of the formation many pyrotl.isiic lotks contain a distinctly more calcic plagioclase (An,, to about AII»:). Some of these pyroclastic rocks contain both bytownilic and labradoritic fragments, but a few contain only bytownilic (or anorthilic) fragments. The feldspars are sharply euhedral and slightly toned. They show abundant simple twinning and some albite twinning. Ciounclmass plagioclases and pl.igiotlases in the matrix of coarse pyroclastic rocks .iic very fine giaineil and cloudy. M.niy are distinctly more soclic than the phenocrysts and range in c.ilcium content down to An,,. In many lapilli tulfs, ihc only feldspar found is alljite (An,); 170 CARIBUtAN GEOLOGICAL INVESTIGATIONS composition uf die more siliceous dilleienliates The experiments of Yodcr jnd Tillcy (1062) show clcaily (hat at water pressures greater than about 1000 bais. material of basaltic composition should If. convened to a mix uirc of liuinblcnde and plagioclasc at sublujiiiiltu temperatmcs. As the temperature rises the material will begin to melt, with the plagioclase being consumed fust. The first liquids produced will be highly felsic and siliceous. The composition^ tfflMl •! liquids produced at successively higher tempei.nines hai IjjjjIiigHppMttrimenially dciermincd, bin a com- paiison with the anj|q^0l4"lpHli!§>' '" anhydrous cases (generation of basalt) suggests thai liorBJhi&im^ll lake the place of diopsidc as the dominant mafic phase being consumed during the greater part of the incit- ing. 1 he h)diuus liquid might, llierefore, be more enriched in Si than would compaiable liipiiils coexisting with diopsidc in the anhydrous case. 'I he extent to which residual hornblende might control the composition of the liquids will not be easily evaluated until these hornblendes can be tollccicd and analyzed, but this consideration might prove lo be pivotal. Tire quantity of keratophyric magmas generated is perhaps the only really serious objection to the hypothesis of generation of this entire suite from the upper mantle. The quantity of siliceous rocks is unknown, but geological inference (exposed aica of Water Island Formation, which is about 80 per cent kcratophyre) combined with geophysical information (seismic refraction and gravity) suggest that the Water Island Formation is a pi ism about 5 km thick, extending perhaps 40 km in an east-west direc- tion, but quite possibly thinning lo the east, and extending perhaps 20 km in a noitli south direction. This volume—4000 cu km, or 3200 cu km of Uiaioph)ic-is piuh.ibly a in.iximum, because possible thinning lo the cast and 10 die soiuli was ignored in the calculation. If fusion of 10 per crni of the upper iimule might yield » keralophyric liquid, then 32,000 in Irn of upper mantle wtie fused during this igneous episode. If the depth of fusion was 10 km and the cast west hoii/ont.il extent of fusion 40 km, linn the liori/ontal dimension of the fused zone in a notth south direction must have been 80 km. These figuics may be off by an order of magnitude or moie. but they emphasize one problem: the generation here of siliceous magma fiom the upper mantle may require the partial fusion of more ma- terial than can directly underlie the vent, unless the fusion extended to great depth The explanation for this seerning paradox is as follows: Dining the orogenic process compression and thickening of hydrated Caribbean mist and u|>|>cr mantle carried this material into the orogen from .1 con- siderable distance perpendicular to the axis of depression. The orogenic iiugm.iiic process then can be compared to a mill lo which is fed fresh, hy- dialed UPJKT m.mile, and from which two products, magma and mafic le minimi, aie icmoicd. the first ilnoiigh ascent and eruption and the second lliioiigh giadual displacement downward and eventually laterally. The .uiioiini ol kriaioplme eiupieil might ha\e lequiied lateral shoi(cuing of .ilinui 60 tin in this .ire*. The ipi.uitiiy of siliceous igneous roik seen licic i» f^r in excess of any that has been recorded in similar orogenic ;oncs, and T. W. P O N N I I L V — ST. THOMAS AND ST. JOHN. II. S. V I K C I N |sl ANUS 171 the Virgin Islands may be an extiemc example of a piotess which has oc currcd to a lesser extent in many places at many limes, (.'leaily our know! edge of the composition of upper m.iiule is loo limited .11 iliis lime lo assess this problem further. 'I he writer (Donnelly, 1964) also pointed out that the generation of a second, strengihless phase (aqueous, or h)diatcd silicate niell) during orogenic thickening would have profound structural implications. The volume in which this phase was generated would become essentially sirengihlcu, and the structural process would be expected to change fiom a relatively mild thickening to a more violent movement along an exten- sive shear. The consequences of this movement would be thai the island platform would be raised to an emergent level, and possibly an adjoining oceanic liench would be funned. The effect on the generation of igneous melts would be that the rate of depression of mantle material (ami the rate of healing) should be increased gieally. After (his profound structural episode, the generation of magma will be relatively rapid, and the propoi- lion of mafic lo fclsic magma high. The restriction of abundant siliceous magmas to the early stages of oiogenic evolution is consistent with this idea. In conclusion, the following points seem well established: (I) Two types of chemically uniform magmas were generated throughout the span of geologic histoty of these islands. (2) Time has been inleradion of erupted magmas with the environment in the case of alkali exchange in extrusive kcralophyres. Other passible exchanges have not been established, except that a few samples of highly metamorphosed keratophyrcs h.i\e been im povcrished in alkalies. (3) The siliceous magmas repieseiit tein.ii) ((.> Ah Oi) melts derived by partial fusion in a dominantly sodic cm mmmriii. and most probably, in an environment with considerable calcium. I lie l.iiei behavior of this presumed calcium remains one of (he important anomalies This parent materi.il, for diverse reasons including geoph)sical ami chemical eu dence, is considered to be upper mantle. (I) The mafic magmas are cheiui cally similar to so called high alumina basalts typical of erogenic regions generally. The high magnesium of the spililcs results from its generation 1 from a material largely depleted in iron by abstraction of keratoph)re (5) The increase in aluminum with lime and the higher noiin.inxc Ab/Q ratio of the later quailz-andcsinc porphyries of the second group may indicate generation at increasing depth with lime. (6) Crystal settling and assimila- tion of wall rock were probably of little importance in ihe grnei.ition 01 differentiation of this suite. SUMMARY OF GEOLOGIC AND TECTONIC HISTORY OF THE NORTHERN VIRGIN ISLANDS Tlie tectonic evolution of the 1'iieito Kico Vii^m M.iinU .IK.I li.i> .il icady been discussed by the writei (Donnelly, 1961) 'I he following account summarising the geologic histoiy of the nonliein Virgin Islands elucidates v r ~1—^ ->~~1 1/2 CMdUIICAN CtOIOCICAL INVfSIICAIIONS these ideas hut introduces no new concepts. The major east-west fault deduced largely (loin gravity evidence was not recogni/cd at the lime that paper was picpjred; however, its existence requires no modification ol tin ideas presented The keratophyies and spilites ol the Watci Ul.md Formation weic cxlinded on a relatively flat tea bottom, as indicated by lack of leiiigenous deliilal sediment ami paucfeK«i~t|«liil|> structures in most lullaceons units A major c.isl-wesi Iiigh-a|f0|fj!f|||p||'ipfeired liorn gi.uily data was prob- ably the locus of eioption «f ides* magmas as well as most of the later magmas. Movements along (tin fault simultaneous with eruplion led in accumulation of the Water Island locks in a basin with a sharply defined northern edge. There is some evidence of shallowing of llie water level towaid the end of Water Island time in the greater ptoportion of lnff.i< cons keratophyres at the very lop of the section. The end of Water Island lime was marked by abrupt emergence, possibly in part along llie major east west fault noted pteviously This movement, as well as subsequent movements along' this fanli. was of an opposite sense 10 the original movement: the northern side went down. Overlying basal Louisenlioj beds weic deposited snbacrially and weathered lo form a brick red soil completely unlike any that are forming at the present lime. Intercalated conglomerates of pic dominant!) keratophyric clasts which are especially abundant near lire base of the Louisenlioj show that there was a rather persistent emergent source aiea of older rocks exposed at this time. Slow subsidence after e.nlv Louiscnhoj lime is reflected in the gradual diminution in abundance ol conglomeratic units, the finer grain size of the pyroclasiic deposits and theii rcuoikcd equivalents, and the increasingly excellent grading of the lull beds toward the lop of the founaiion. The overlying Outer Hi ass Lime- stone represents almost complete volcanic quiescence and subsidence below the level of effective wave erosion of the older rock units. The beginning of Tutu lime was the beginning of renewed dificic-niial xcilical movement, with newly Cleared or rejuvenated sleep slopes shedding ivjckcs into water of unknown depth, tmeigemc of pail of llic sotnce area is seen in the abundance of partially wcalheicd Louisenlioj fiagmenls among the denilal component of the Tutu Founaiion ami ii; lire irrlei calated blocks of fossiliferous limestone of the Coki I'oint Megabicrcia lithofacies. A brief period of ncai-cmeigcncc is seen in the Congo Cay Limestone Member The iccryslalliralion of this unit is too extensive lo have preserved any of the diagnostic peirogiaphic ciileiia which might have revealed something of iis environment ol deposition, but its massive- ness and iH.nl) pnie cahilic ((imposition shows that il nnisl have been a bank deposit of neatly pine skeletal debt is Renewed vnlcanism after Tulu time is seen in the thick augile andesitc p)ioclasiic rocks of the llans Lollik Foim.ilion. Mineialo*;ically this andesile appears lo be identical lo dial of die Louisenlioj Formation. I'osl Hairs Lollik Founaiion history is obstnre in die American islands T. W. DONNLI I V—SI. IIKIMAS AND SI. JOHN. II. S VIKI.IN 1st ANUS | 7!) and has been treated in moie ilctail by llelsley (I'JOO thesis) in the Iliitisli Viigiu Islands. A dale of Muldlc I occne near the lop of the 'loiml.i I-'01111.1- lion (which includes the Ham Lollik Formation, called by HeUcv a member, in (he llrilish islands) establishes the age of the upper pail of tin Virgin Islands Gioup The l.nye li.uholilh in the Iliilish islands iniunlo llie Toilola Formation and is app.nently conieiiipoiaiieoiis uiili the mm fossililcious Keeker Koimaiion. llori<onlal forces of any oiieiil.iiion 01 sense cannot be shoun in h.iu- played an ini|>oiianl iole at any stage dining the evuliiintn ol this .ne.i Neaily all the sliurluial relalionJiips obsetved. as vvell as llie ph)>ii.il Slialigiaphic di.uai lei of the lot I units, can be mine c-asily explained on (de- basis of dilleieniial vcilK.il inoveinenis. M.my fault planes atios> ivhiih such movements oiiinied may have continued to be the loci of fault dii placemrnts fiom Oelaceous lo eaily Teitiary lime, ami even In the pus ent.* The pioblem of the geiieialion of the magmas is iueMiic.ibly linked u-iili that of the sniiclnial evolution of the aic. The geiieialion of all of ihe magmas is considered to have occulted as a result of the. moie or less par lial fusion of hydratcd upper mantle inaleiial, ideniical lo ih.it piesenily found beneath the Caiibbean Sea at depths between 5 and lf> 01 20 km below the sea floor. The large volume of siliceous keratopliyie, and to a Icssei extent, the volume of later mafic locks, leqiiiies the fusion of np|" i mantle over a hoiiiontal extent considerably greater than the piesc-nt di meiisions of the omcioppiirg rock units. If llic fusion vc.is limited to the hydiatetl 10 lo 15 km of upper mantle, then tlie only adecjiiate expl.ni.i lion for the volume of magma erupted is that hoii/ontal movements n.m> ported adjacent, unfnsed m.inllc into the orogen, where il was depressed. healed, partially fused, and then its refiactoty lesiclmmi slnuly clispl.Keil downwaid and laterally. The evolution of this poilion of the UVsl Imlies is basic.illy llie (espouse of juxtaposed, physically contrasting plates of crnsl arid upper mantle 10 an applied horizontal force. Fnilme along llic join between these plates resulted in thickening and clownwaiping in the initial stages (Water Island lime), followed by compressive faihnc, the formation of a major r e v e r s e fault system, and rapid uplift, which foimed an emergent island pl.ufoiin (Louisenlioj lime) and, most probably, an adjoining oceanic tieriili Knrilu-i application of compressive foiccs caused further thickening and continued emcigcnce of llie island platform. 'I here is no evidence in the V'iigin Islands that submergence of any magnitude ever occuned alter U'aiei Island lime. Magma was generated by the partial fusion of hvduud upper mantle; the proportion of siliceous and mafic magmas at any time reflects the rale of deformation and lire i.ileof lemperaiuie lise. The eastern Greater Antilles is a unique exhibit of the s.dicin (t.iiini-s •s>« (iNiuioir 2. j'Jgi- MO T i —j —j ____ __^ _ __ __ ^ _ ___ _ . .__ _^ _ „_ I - ^^_^j V __ _;• *"*•• ___^ **„ 17-1 CABIObLAN CLOLOCICAL INVESTIGATIONS ol the caith's island arcs. This area has never been blanketed with the thick teriigcuous sediments which have modified and later guided the iituciur.il evolution of most oiogenic legions; it repiesents instead the diiect interaction of oceanic oust and erogenic forces. Ihe failure of these rocks to have been metamorphosed und their subsequent cxhuni.iiion in a neatly pristine condition at* ptptably the result of a lucky geologic.il accident—the development ijf wr^fetcnsivc strike slip fault system south of the island platform along wftf»l»^8lre resolved the bulk of the post-Eocene cleforinative forces. \Vilhiu the bland phlfoim. the <lomin:ini tectonic forces have been differential vertical movement* caused hy thickening ill depth Although none of llie structural or pelrologit conclusions dctived from this study can necessarily be applied to any oilier sjKcific area, nevertheless certain observations cannot fail to raise serious questions con- cerning long standing geological hypotheses which have not been seriously ijucstioncJ in icccnt years. REFERENCES CITED UocbiLB. O. B. 1907. Oio Dansk-Vcsiindicns Ceologi: Ceogranik Ttdsskiifl. Kon. Uansks. Ceograph. Sclskab. v. 19. p. 6-11 (Translated by Mil Edith Theile. Torlola. H VI. and eiatuined by the writer) Duf.tr. f.. 1956. ZoniCcacion microlaunislica de lai caliiai cielacicai del esie dc Mexico: Dol AUK. Pciiol Men . v. 8. p 389-187 UUHIN. N. I... and Tumt. O. F.. 1950. The S)siem NaAISi.O, KAISi.O. II.O: Jour. Ccol ogy. v 54. p 489-511 Hii.uiNiroi. A. F.. 1959. Cianiie cniplaccnu-nl with special icleieiice lo N'onls America: An cuj) it lies.: Ccol. Soc. Ameiica Dull., v. 70. p. 671-748 Cij.ii. Pia Tiouou. 1871. On Ihe geolufy of Uie noiiheaslern Well India Islands: Slock,- holm. Kungl. Svcnska Veiensk.-Akad. lljndl.. no 12. p. 1-18. —— 1881. Outline of the geology of the noiiheaslern Wcsl India Islands: N. V. Acad. Sci. Annali, v. 21. p. 185-192 CuHMUUl, II P., 1951. /ur Fiage der Absalibcdingunden dcr Radiolaiile: Ccol. Rund.. Bd 38. p 216-221 UU-.MIH. T. W. 1959, The geology of Si. Thomal and Si. John. Viigin Islands: 2d Caribbean Ccol Conf. Tuns. (Ma)aguci. Pueilo Rico), p. 153-155 —— 1962. U'jirakitc in West Indian spililic rocU: Am. Mineialogisl. v. 47. p. 791-802 —— 1963. Gcnois of albile in eaily oiogenic volcanic rods: Am. Jour. Sci.. v .261. p. 957- 972 —— 1961, Evolution of eastern Antilleaii island arc: Am. Assoc. Pctioliom Geologists Hull, v 48. p 680-696 —— 1965. Sea bottom morphology suggestive of post Pleistocene tectonic activity of the eastern Greater Antilles: Ccol. Soc. America Bull., v. 76. p. 1291 -1291 —UL.CJIASSAING. P.. and MiCJitLOTTi, C.. 1861. 1166. Memoire »ur let Coralliariri del Antilles: Men. Acad Tuiin. 2d ser. v. 19. p. 279-S6S; v. 23. p. 199 EAIU. K XV . 1924. 1 he geology of llie milish Viigin Islan.li: Ceol. Mag . v 61. p. 339- 351 Inc. W. S, 'It KM*. F. J. and VIKIIOOCCN, J.. 1958. Meumoi|>hic teactions and men inorphic facies: Ceol Soc. America Memoir 73. 260 p. • Not eiaiained by the writer T. W. DONNEILV—ST. THOMAS AND ST. JOHN. U. S. VIRGIN lit ANDS | 75 HAMILION. W . 1964. Origin of high alumina basalt, andesite. and dacitc magmas: Sciciue. v. 146. p 6J5 637 MlMiiir. J. J. 1959. Some mliieialogit.il equilibria in the ijiicm K;O AI,O. SiO, II.O Am. Jour Sci. v. 257. p 241-270 lliMlir, J J.. Mint. C.. ami Rtciitn, D. II. 1961, Some jlirniion nj.iions in the lysiem Na.O AI.O. Sit), II.O: 1). S Giol Suuey I'liif I'jji. r 4211). |i. 3'JH 310 IliiS. II. II, 1'JI'J. Chemical composition and o|'liul |>i«|>ciiui ol common clinii|>)in\i m v Paul: ^n Mineialogiil. v. 34. p 62l-6l>6 HCM.IMJM, A. C. 1905. 7ui Peliogiaplm- iler Mi hit n Annllcn (l|.u|j. Hull (,i.,l I., i Univ . v 6 (I902-IU03). p 214-232 •IIOKNsiii.il, II n, 1810. Noglc UeinaeiLiiinyer oiei !>t 1 IH.IIUI (,I,,I.H,IH MJII.|IHJVJ>|.I NaiuilorsLcics. '.'del Mode, p 361-368 •—— 1816. llebcr die inincralischcn Vorkommniiie Jill d< i Intel Si I |II>IIMS. Kiel. 2hli Veil der Natuif. und Aerite. p. 262 261 KtMr. J. F.. 1926. Geology of the Viigin Islandi. Culcbta. and Viiijues: Inlioduciion and review of ihe literature: N. V. Aci.l Sci. Scientific Survey of I'orto Rico and llie Viigin Islands, v. 4. |>t I. p. I-6'J KiNNUv. C. C.. IU50, PICUUIC volume temperature relations in water at elevated Inn- peiaiuics and pretsuies: AID. Jour. Sci, v. 248. p. 540-564 •K.MOI. Rrv. J. p., 1852. A hiitorical account of Si. Thoniu, W.I : New Voil, Chailes Sciibner and Sons. p. 207-213 LEMMUIN. C. C.. and Kcivrsov. P. W.. 1956. (The rclaiionship of the theioiodynaniical paiaroclcil P-T-V for II,O and 30% aqueous NaCI solutions): Mm Sue. U S S R Tram. v. 85. p. 529-534 I.IOIAK, E. C.. 1965. Penology of andesitic, ipililic, and keraio|>h)iic flow toil., nonh central Puerio Rico: Ceol. Soc. America Dull. v. 76. p. 57 88 •MACtUM. W. 1817. Observations on Ihe geology ol (he West Indij ivlands li,<m lljil,j,l,-t 10 Santa Ciui, inclusive: Philadelphia, Jour Arid. Sii. v. I. p 151 HO Mctuiiorr. II. A.. 1926. Geology of Ihe Viigin Islands. Culil.u. and Viei|iu> I'l.jnog raphy: N. V. Acad. Sci., Scientific Suncy of I'ono Rico ami the Virgin Itbmh. v 4. pi. I. p. 71-141; pi. 2. p. 1-219 Niciiotu. C. U.. 1959. Automelasomatisni in ihe lower Sfiilitcs of the Uuilcli lolcann. series: Quail. Jour. Ceol. Soc. l/mdon. v. 114. p. 137-162 Noctourt, S. R.. and AIUN, R.. 1953, The gcochcmisliy of some igneous rock series. Ccocliim. el Cosmochim Acia. v. 4. p. 105-142 Orricm. C. D. EWINC, J. I. HSNNION. J. F.. IUm«jot«. O. C . and Milieu. I). E. 1959. Ccoph)sical investigations in ihe cjstcin Caribbean: summary of 1955 and 1956 cruises, p. 17-109 in L. II. Ahicns, F. 1'icss. K Rankama. anil S K Rnncoin. E.lilot,. I'hysici and Chcmistiy of ihe Earth. Volume 3. London, Pugjinoii Pros, •)<>( p. OIVIILC. P. M.. 1963. Alkali ion exchange lietwim vapor and fcldipai plusc: Am Jour Sci.. v. 261. p. 201-2)7 OS«O«M. t. F.. 1959. Hole of ov)(jfn pieuuic- in (lie cr)sialliiJii»n an<l dilleieniuii,,ii i.l basaltic magma: Am. Jour Sci. v. 757. p. 609-617 Rdstlt. II. J.. I960. Zur Pcliographic. Ccocheinie und Cenesc dcr Magiiuinr nnd l.a|;ri slillcn del OUidevoni und Unterkarbons in Onihiirinurn: rreil/<igit luixliunj; C 92. p. 1-275 SCIHMN, K., 1962. Semi-quanlilative anal)iis of chloritcs by X iay iliHrj<IH..I \m Mm eral^ist. v. 47. p. 1384-1392 •ScilOMiutc*. R II.. 1837. Die Jungfian Inicln. in geologitchei unit Lhn.n nlm llnnulii Berghaus' Almanach liii Erdknnde. p 367H55 Siuriao. L.. and BXNNOCK. W. W.. 1962. Rapid analpis of silujte, cjiLuiutr. Jiul ),!,„> phaic locks: U. S. Ceol. Suvey Hull. 1141 A. 56 p. SIIUUCT, C. L, Woniri, J. L.. and EWINC. M.. 1956, Gravity measuicmrnis in the Virgin Islands: Ccol. Sue. America Bull. v. 67. p. 1529-1536 ift I L E G E N D Quaternary Alluvium U Cretaceous L Tertiary Dike* and Plugs: qo« quartz-andesine porphyry; ah* andesine-hornblende porphyry Contact Fault, showing displacement Cretaceous (Albion ? ) a. 3 O o Khl i g i • > Kl tf Dioritic Rocks Hans Lollik Fm.: Augite andesite volcanic breccia and tuff • Tutu Fm: Volcanic wacke. X-cp outcrop of 1 Coki Point Megabreccla -1 Ktcc - Congo Cay Li. Member 1 Outer Brass Ls.:Thin-bedded, siliceous Is. Louisenhoj Fm.. Augite andesite volcanic t and tuff, with minor conglomerate Attitude of bedding Attitude of fault Attitude of intrusive contact UNCONFORMITY in § a>oo Quartz keratophyre dikes and plugs O 0) o Water Island Fm.: Quartz kerotophyre flows, flow 11 I breccias,and tuffs; radiolarites, spilite flows M1PPCO BT THOMAS W DONNELLT (l»5«-1*571 SOUIHWCtT TOUTOL* BY C ( HILSLCf (!•»*) REFERENCE NO. 12 ISSN 0500-4780 CLIMATOLOGICAL DATA ANNUAL SUMMARY PUERTO RICO AND VIRGIN ISLANDS 1987 VOLUME 33 NUMBER 13 I C E R T I F Y THAT THIS IS AN O F F I C I A L P U B L I C A T I O N OF THE N A T I O N A L OCEANIC AND ATMOSPHERIC A D M I N I S T R A T I O N AND IS COMPILED FROM I N F O R M A T I O N R E C E I V E D AT THE N A T I O N A L CLIMATIC DATA CENTER, ASHEVILLE NORTH CAROLINA' -<i 28801 DIRECTOR NATIONAL CLIMATIC DATA CENTER noaa NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION NATIONAL ENVIRONMENTAL SATELLITE. DATA AND INFORMATION SERVICE NATIONAL CLIMATIC DATA CENTER ASHEVILLE NORTH CAROLINA TOTAL PRECIPITATION AND DEPARTURES FROM NORMAL (INCHES P U E R T O R I C O A N D V I R G I N I S L A N D S I 9B7 S T A T I O N V I R G I N I S L A N D S • ' , .3 ST T H O M A S 01 D O R O T H E A A E S E S T A T E F O R T M r L N E H E S T A T E HOPE R E D H O O K B A T T R U M A N F L O F A A A P M 1 N T B E R G - - D I V I S I O N A L D A T A - - - - - - - > ST CRO 1 X 02 A L E X H A M I L T O N F L O F A A A N N A L V A N N A S HOPE B E T H UPPER N E H W O R K S C H A 1 S T I A N S T E D F O R T C O T T O N V A L L E Y 2 E A S T H I L L E S T A T E T H E S I G H T F O U N T A 1 N F R E D E R I K S T E O 1 SE G R A N A R O HAH B L U F F L - H S TN n O N T P E L L 1 ER - -01 V 1 S 1 O N A L D A T A - - - - - - - > ST JOHN 03 C A N E E L B A T P L A N T A T I O N G A T H E R 1 NEBURG C O R A L B A T C R U Z B A T E A S T E N D L A H E S H U R B A V - - D I V I S I O N A L D A T A - - - - - - - > -/ JUL PHECIP / ' ' \ .92 9.04 I . •• 1 . 22 . 99 . 93 1 40 1 . 22 2 . 28 i ao 1 92 2 . 28 2 . 50 1 . 4 6 2 . 20 3 . 00 2 3 1 1 . 5 7 1 . 95 2 . 5 5 2 . 06 1 . 7 4 2 . 02 1 . 7 4 1 . 5 9 2 . 1 0 1 . 6 5 1 . 6 1 DEPARIURE - 1 85 - 2 . 1 4 - 1 . <? 2 - 1 . 1 7 - 2 . 1 1 - 1 . 4 4 A U G PRECIP 2 7 2 2 . 76 2 96 1 . 69 2 . 4 1 1 . 5 3 2 2 2 6 3 60 . 25 32 . 66 H . 1 3 . B 1 . 9 1 2 . 09 . 45 . 62 . 38 1 . 5 2 2 . 1 5 2 20 1 2 . 2 7 1 . 8 8 1 . 90 2 . 0 8 DEPARIURE - 2 38 - 2 84 - 3 . 1 2 - 3 . 0 8 - 2 . 0 2 - 2 . 5 2 S E P PRECIP 2 . 5 7 . 40 2 . 90 1 . 6 6 1 . 4 2 1 . 4 3 1 . 5 0 2 7 9 2 . 09 1 . 50 2 . 02 1 . 4 3 H 1 . 4 5 1 2 3 1 . 5 0 2 92 1 . 1 8 1 . 4 2 2 . 1 0 1 . 80 2 2 3 1 . 2 2 3 . 6 5 2 . 4 2 2 . 0 6 H 2 . 3 2 DEPARTURE - 4 60 - 2 64 - 4 5 3 - 4 30 - 3 . 5 5 - 3 76 OC T PRECIP 4 . 5 3 4 . 3 2 4 . 5 7 3 . 9 7 4 35 3 . 5 3 4 . 1 4 2 65 2 80 4 1 0 M 2 5 5 3 7 6 3 8 6 5 1 3 4 86 3 . 00 2 52 3 . 1 7 M 2 . 3 3 4 . 6 3 3 1 a . b B 5 . 0 7 5 . 2 7 3 . 56 3 . 7 5 3 . 08 H 3 . 0 8 4 . 1 5 OIPARIURE - 1 2 7 - 2 60 - . 9 7 - 1 . 7 3 - 1 . 3 7 - 1 . 2b NO V PRICIP 1 8 4 7 1 7 3 7 1 2 9 1 1 1 4 9 1 0 3b 1 0 4 3 1 3 b 2 1 3 2 5 1 5 0 3 1 1 4 5 1 5 2 7 1 5 4 8 10 17 1 3 . 8 0 1 4 . 5 1 1 5 . 2 3 1 5 . 7b M 1 b . 95 1 3 7 6 1 4 2 2 1 2 6b 1 3 . 0 8 1 1 5 2 8 . 5 4 1 0 . 3 9 1 0 . b 4 1 1 . 1 7 OCPARIURE 8 5 1 8 2 3 5 8b 9 1 1 4 0 3 6 0 6 D E C we IP 4 . 4 3 5 . 6 5 4 . 2 7 2 3 2 2 99 4 1 3 3 SO 4 9 4 3 . 5 2 M 4 b2 3 7 3 2 39 3 1 9 2 9b 5 5 0 3 7 4 M 2 . 9b 4 4 2 3 . 8 2 3 "JO M 4 4 2 4 5 6 M 3 6 7 4 0 4 4 0 4 DEP«R1UR( 1 ^ 9b 04 2b A N N U A L PRfCIP 7 0 . 1 7 6 7 . 6 6 4 1 . 3 7 4 2 . 8 4 5 0 . 0 8 5 3 9 7 M 5 0 1 0 58 1 fa M 4 8 . 8 S 5 5 5 1 5 4 8 S 5 8 . 1 0 b 1 . fa 7 5b . 75 M 5 9 . 0 2 5 8 7 B 5 5 . 2 1 4 8 2 2 M 4 9 4 7 40 bl 4 4 Sb DEPARIURE < 1 0 2 3 « n 1 1 4 7 1 2 2 S E E R E F E R E N C E N O T E S F O L L O W I N G S T A T I O N I N D E X 7 AVERAGE TE S T A T I O N O U T L T I N G ISLANDS 07 HONA ISLAND 2 V1EOUES ISLAND 12 VIRGIN ISLANDS ST THOMAS 01 DOROTHEA AES RED HOOK BAT TRUMAN FLO FAA AP - - D I V I S I O N A L D A T A - - - - - - - » ST C R O I X 02 •LEX HAMILTON FLO FAA ANNALT BCTH UPPER NEU WORKS CHRISTIANSTED FORT ST JOHN 03 CATHERINEBURG CRUZ BAT J A N 1 175.7 It 4 75 7 1 1 78 8 78 3 178 3 1 1 177 8 78 1 174 3 177 7 7b 0 * T 1 7 1 5 - b EEB i 4< 75.5 75 b 75.5 75 b 1 79. 1 77 8 77 a 1 1 7b a 77 3 175 9 77 2 7b b S 1 2 . 7 0 1PERATURES AND M A R £ 1 ft 7b 3 7b 5 7b 3 75 b 1 78 9 77 5 77 9 1 171 1 1 74 5 175 1 77 7 7b 4 S s 3 -2 7 - 8 A P R £ 1 * 79 e 78 7 79 8 78 b 1 81 7 80 2 81 3 1 1 1 81 3 178 3 181 0 79 7 5 S i a 3 9 1 3 M A Y m; ft 80 4 179 5 80 4 78 7 1 81 4 80 1 80 b 1 1 1 80 b 177 7 181 3 79 5 S 3 3 8 - 3 DEPARTURES EROM NORMAL (° JUN § s i 79 1 179 9 1 82 4 81 2 82 b 1 1 1 82 b 178 4 182 7 80 b S' - 2 1 2 - a JUL « * 83 2 80 0 83 2 181 4 1 83 8 82 b 83 9 1 1 1 83 9 178 9 183 2 81 1 ' B 2 1 - 7 A U G « * 84 4 81 7 84 4 82 5 1 85 1 83 B 184 7 1 1 1 84 7 180 b 184 5 82 b - 1 9 2 8 7 S E P s/ s 83 4 81 9 83 4 82 1 1 85 1 83 7 84 1 82 1 1 (84 3 83 5 181 9 83 8 82 9 s 2 3 2 1 1 5 OC T I s 1 BO B 81 4 1 83 9 82 7 83 4 1 1 82 8 83 1 179 b 183 2 81 4 g ; 1 8 2 2 - i PUERTO R I C O AND - J V I R G I N ISLANDS N O V s * 1 79 0 78 9 1 82 3 80 b 82 2 1 1 180 b 81 4 177 3 81 B 79 b ae z 1 3 2 1 3 D E C i 179 7 7B I 79 7 7b 5 1 81 0 78 8 81 0 1 178 5 79 4 79 b 17b 2 1 7b 2 3M1VP430 1 3 2 1 1 3 ANNUAL I mi 178 9 1 1 B2 O 80 b 181 5 1 1 1 80 9 1 7 7 9 1 79 4 f 1 2 1 5 0 SCC RCrCMNCC INKS FOUOHIM SUIION INOCI 5 REFERENCE NO. 13 ESTIMATED WATER USE IN 3L THOMAS, U.S. VIRGIN SUNOS, JULY 1983 -JUNE 1984 By Heriberto Torres-Sierra and Rafaei Dacosta Prepared in cooperation with the CARIBBEAN RESEARCH INSTITUTE COLLEGE OF THE VIRGIN ISLANDS ST. THOMAS. U.S. VIRGIN ISLANDS DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY WATER RESOURCES DIVISION OPEN-FILE DATA REPORT 84-721 • in OO 7 016.1 ESTIMATED WATER USE iN ST. THOMAS, U.S. VIRGIN ISLANDS, JULY '983 • JUNE *984 By Heriberto Torres-Sierra and Rafaei Dacosta INTRODUCTION Water use data (withdrawal and return amounts) has always been the ~ost difficult element co define in the nydroiogic cycle. The need to determine the amount of water used to meet public, commercial and domestic p.eeds among other uses is essential where the available supply is inadequate. In St. Thomas, U.S. Virgin Islands, where streamflow occurs mostly during periods of intense rainstorms and ground-water resources are limited (Jordan and Cosner, 1973), water-use information is critical. In 1983, the U.S. Geolog- ical Survey, Water Resources Division, in cooperation with the Water Resources Research Institute of the College of the Virgin Islands, began a general- ized inventory of water use in St. Thomas. St. Thomas is located about 20 miles east of Puerto Rico (fig. 1). The island's popula- tion increased from 16,000 in 1960 to more than -^7,500 in 1984, paralleled with an in- crease lit water production to meet tPlK public water-supply demandiKfe. 2). vater demands have increased also in response to tourism development. Although the production of water increas- ed with the installation of a large-scale seawater desalina- tion plant by the Government cf the U.S. Virgin Islands, the demand has not been satisfied. '•nlv loout -•) rercsnt -f the vater produced is accounted for, mostly uue ;o losses from leakage in ihe distribution system installed in 1949 (Priede- Sedgwick, Inc., i979). Other losses are jue co unauthorized connections, faulty meters, and uncontrolled public faucets (fig. 3). WATER SOURCES AND USES The principal sources and uses of water in St. Thomas are shown in -ig. •+. Seawater, rainfall collected from residen- tial roof-top catchments, and ground water are the main water sources in the island. Thermo- electric-power generation, pub- lic-water supply, and domestic and commercial self-supply are the principal uses. Seawater is used indirectly as the source of condenser-cool- ing water by the Virgin Islands Water and Power Authority (WAPA). The waste heat from the Island thermoelectric facility (fig. 5a) is used by the seawater-de- salination plant (fig. 5b). Desalinated water from storage tanks (fig. 5c) is distributed to the urban areas in Charlotte Aroalie (fig. 5d), by the Virgin Islands Public Works Department (VIPWD). Areas outside the public-water supply distribution system, such as the Donoe housing project at N'ew, (fig. 5e) can be classified as self- supplied users. These obtain their water supply from rainfall catchments, wells, or from com- mercial water haulers (fig. 5f). U.S. GEOLOGICAL SURVEY WATER RESOURCES DIVISION 'TUT The main urban area of Charlotte Amalie is also served by a seawater system. This system supplies water for fire fighting and flushing of toilets and open drains. Areas outside the seawater system depend on "gray water" (wasteuater from other household uses) as their source of water for flushing toilets or irrigation. Where aquifers yield significant water to wells (10 gal/trin or more) these are also tapped as a source of water, even if saline, as feed tor reverse osmosis units or for flushing. Bottled water produced locally or imported is an important drinking water source. Bottled water costs approximate- ly SI.25 per gallon. In 1979 importation of bottled water was estimated at 1,600 gal/d (Peebles, 1979). There are no reliable figures for current imports. Publlc-Wattr Supply Production of desalinated water during the study period averaged 2.4 million gallons per day (Mgal/d). Only about 0.9 Hgal/d (38 percent) was accounted (revenues from sales) by the VIPUD. About 1.5 Mgal/d was unaccounted for as previously indicated. A recent investiga- tion showed that leakage in tht distribution system represents 30 to 40 percent of the total losses (CH2M Hill Southeast. 1983). The production of desalina- ted water for public supply increased to a peak of about 2.4 Mgal/d in 1975, declining thereafter to less than 0.6 Mgal/d in 1980. Since 1981. WAPA has Installed three new desalination units with a total rated capacity of 3.1 Mgal/d. At present only two units are being operated. Full production capacity will be required when the East End Transmission System becomes operational (fig. 6). This distribution system was constructed in 1977 but haa not been utilized. Water pumped to the seawater distribution-system averages 1.0 Mgal/d. Only about 0.3S Mgal/d of this amount is accounted for at the public sewage treatment plant serving Charlotte Amalie. The remainder may be lost through leaks in the: seawater-distrlbutlon system. However, various storm drains in Charlotte Ana He are continuously flushed to the ocean by taps from the seawater- distribution system. Discharge from two of these taps were measured and had an average flow of 0.08 Mgal/d each. Five of these taps would account for !s of the unaccounted flow.. The cost of potable water to WAPA from the desalination units is about 59.00 per thousand gallons (S9.00/kgal). This does not include amortiza- tion costs of the desalination units (Ajayi and Conez, 1983). The actual costs charged by VIPWD to consumers connected to the distribution system is S14/kgal (VIPWD personal communi- cation, 1984). Generaf/on Thermoelectric-Power Gene- ration is the largest single water use category in St. Thomas. Total use was about 67 Mgal/d. This was essentially seawater, except about one percent freshwater obtained directly from the desalination plant for boiler feed. Domtftlc S»lf-Suppll«d - ffa/nra// About two-thirds of the population in St. Thomas is not served by the potable public water supply distribution system, and thus classified as domestic self-supplied. Rain- water collected from rooftop catchment systems and stored in cisterns, and withdrawals from ground water are the sources for domestic self-supply. Estimated water use for this category was about 0.75 Mgal/d. Of this amount, 0.60 Mgal/d (80 percent) vaa supplied from rainfall. This indicates that rooftop catchments are a major source of water for most private homes especially in the more humid areas of the Island (fig. 7). Virgin Islands law requires all dwellings, apartments and hotels to have a minimum cistern storage of 10 gallons for each square foot of roof area for one story buildings, and IS gallons for each square foot of roof area for two or more story buildings. All other buildings ea*oo' 0163 ATLANTIC OCEAN E2. Ill 0. a O •00'- are required to have cisterns with a minimum useable capacity of 4*5 gallons per square foot of roof area except churches and warehouses, which are not required to con fora to this standard (Jordan and Cosner, 1973). A comparison of yields bf" "en rooftop-rainfall catch- «• at a high rainfall (Doro- th»—, and at a low rainfall area (Red Hook), was made using data from July 1983 to June 1984. The comparison was made for a family of four using 25 gallons per capita per day (25 gpcdl with a roof area of 1,000 ft and an initially full cistern (10,000 gal). The family would have required the services of a water hauler only once If they lived in the Dorothea area, and twice if they lived in the Red Hook area. Rainfall could have supplied about 50 percent of the total water needs in the Dorothea area, but only 31 percent at Red Hook. The cost of water produced by household roof-top cistern systems Is estimated at $17 to S19/kgal (CH2M Hill Southeast, 1983). The major cost is associated with construction of a cistern. Domestic Self-Supplied - Ground Wtter Ground water withdrawn for domestic self-supplied use was about 0.15 Hgal/d. Ground-water withdrawals by the Virgin I- ds Housing Authority (V1HA) w •stimated at 0.10 Hgal/d. Ari^-additional 0.05 Mgal/d was used by other domestic self- supplied users. Ground water for domestic use is available In nearly all parts of the island. There are only a few areas where yields to wells are large enough to warrant the development of public supplies. In their study. Jordan and Cosner divided the island into five ground-water areas according to their poten- tial yield and water quality (fig. 8). The potential yield ana waier quaxity 01 tnese areas are limited by excessive depth to water, seawater intrusion, waste-water contamination, and contamination from seawater mains. Commercial Self-Supplied Condominiums and hotels used about 2.0 Hgal/d of saline water. This is used principally for cooling, flushing toilets, and swimming pools. Small desalination plants produce about 0.1 Hgal/d freshwater. About 0.2 Mgal/d of the commercial water-use is ground water. This is used mostly for flushing toilets. In some areas, where the ground water is of good quality, the waste water is used for irrigation of lawns (Mahogany Run). However, most of the commercial facilities are located near the coast and pump saline-ground water. Water haulers supplied an estimated 0.07 Hgal/d of desalin- ated water from the VIPVD standplpes to commercial users. The average price of water delivered by water haulers is $55/kgal (AJayi and G6m«t-C6mez, 1983). An estimated amount of 0.05 Hgal/d was obtained from rooftop rainfall catchments. Public Wette-Water Treatment There are seven public waste-water treatment facilities in St. Thomas (fig. 9). The airport plant, serving Charlotte Amalie, discharges about 0.5 Hgal/d to the ocean. Instantan- eous flow rates measured in June 1984 ranged from 0.16 to 1.4 Mgal/d (fig. 10). Specific conductance measurements Indica- ted that about 70 percent of the effluent was seawater. The other six waate-water treatment plants serve mostly public-housing projects. These discharge about 0.20 Mgal/d to streams and the ocean. SOURCE, DISTRIB FIOUHe tt. Seaeiefer Intuit at rae T*»rmo»lt1trlc Pover Hmmt tt Krmm *ajr (Sub ••••;. < d. Oe»eatfc aad coataierclaf vaerf »t Caarfotr* Aatafla area. [~~| Area terved Pipeline Insulted but not operational as ol July 1«*4. Aree* not Mneit 0 1 2 3 4 MILES Ban (0. FIOU*e f. Area* terretf by r»e /race-water dlttHbutlon «?«rem. F/Ol 0 1 2 3 4 MILES FlOUne r. A*»r*o*-*mt**l r*l»t*ll. In /«»•« /Prepared », K.J. CeJm»ert. (HWS) HO A A.) FIOUHE 3. Comemrlfoa ot Ih* qututlty ol wmttr antrlbmtd REFERENCE NO. 14 A T L A N T I C O C E A N C A R I B B E A N S E A U.S. Virgin Islands Dept. of Planning and Natural Resources Coastal Zone Management Program Preparation of IM* HMp WM flninccd Mi part under UM CowUI ZOrw MMwgcnwnl Act ol ItTI, *d<ntnMMwl by UM Otftc* ot CoMlM ZOM M«n»g»in«m, NMtoMl OcMnlc and AUmwprM<1c AdmmMMIen. ZONING DISTRICTS LEGEND Low Dentilv. Retid«nti«l low Ontitv. Retideniul Oeninv, ftmdentitl Dtnttw. Rmdentul High Dentitv. Rmdentul Ctnlrtt Buti Secondarv B Scattered Bu COAST At LAND AND WATER USE PLAN I Preservation M Conservation Recreation, Traditional Uses I 1 Protection, Residential Low Densilv | Residential. Medium Density | Residential, High Density Lj Water Dependent & Related Commercial Marine Facilities | Water Dependent & Related Industrial Marine Facilities fm Commercial [J Industrial 5^3 Excluded Federal Land R-1 It-2 R-3 It -4 R-5 8-1 1-2 8-1 8 4 C Commefcul 1-1 A 1-2 Ughi and H«jw induttru1 W-1 W-2 Waterfront - Pleasure Wateftroni • Industrial Puot ic 'Government ST 'OH '3* DATE: JAN 06 UNITED STATEb ENVIRONMENTAL PROTECTION ACacNCY REGION II Preliminary Assessment and Confirmation of Authorization of ">JECT: CERCLA Removal Action Monies for the TUTU Well site, Anna's Retreat, Saint Thomas, U.S. Virgin Islands - ACTION MEMORANDUM FROM: TO: Carlos E. O'Neill On-Scene Coordinator Stephen D. Luftig, Director Emergency and Remedial Response Division THRU: George H. zachos, Acting Chief Response and Prevention Branch I. EXECUTIVE SUMMARY — On July 15, 1987, Mr. Allan Smith, Commissioner of the Department of Planning and Natural Resources (DPNR), U.S. Virgin Islands, verbally requested that the U.S. Environmental Protection Agency (EPA) provide analytical support in the sampling of one well which was reported to exhibit a strong unpleasant odor. This well is a major source of commercially provided potable water supply for the eastern portion of St. Thomas. The well is located on the eastern part of the island in the Tutu Section of Anna's Retreat./ This verbal request was followed by an additional request for EPA to assume the role of Lead Agency after sampling results indicated that several commercial wells were found to be contaminated with hazardous substances. This verbal request was followed by a ^~ formal request in writing by DPNR on August 10, 1987. In July and August of 1987, EPA confirmed by sampling and analysis, the contamination of groundwater with volatile organic compounds. A major contaminant in the groundwater is tetrachloroethylene (TCE). The EPA 10-Day Health Advisory Level of 175 ppb was exceeded in three (3) of twenty four (24) wells sampled, with two of the three contaminated wells being private residential wells. ^ The concentrations found ranged __ from 240 to 7,600 ppb with seven (7) additional wells being below the EPA 10-Day Health Advisory, but above the U.S. virgin Island's interim maximum permissible concentration levels set on September 1, 1987, by DPNR for volatile organics in drinking water in tfc* Turpentine Run Aquifer (50 ppb for a single com- pound or 190 ppb for total volatile organic compounds). Three of the previously mentioned seven wells were residential wells. REQION II FORM 132O-1 (•/Ml -2- This Action Memorandum will document funding authorized for phase I of the Tutu Well Site CKRCLA Removal Action. Phase I addresses only residences having contaminated drinking water wells with volatile organic compounds above levels established by the U.S.V.I.'s interim maximum permissible concentration levels for potable water. This action did not include wells where water is used primarily for commercial, business, industrial and/or trade purposes. It also did not include wells contaminated solely by gasoline or gasoline by-products which are not hazardous substances within the definition of Section 101(14) of CERCLA. This action includes the decontam- ination and cleaning of residential cisterns contaminated by hazardous substances, the modification of plumbing, the delivery of water by tank trucks as a temporary alternate water supply, and a well water monitoring program. The total project ceiling authorized for a 52-week period is $100,000 of which $40,000 is estimated for mitigation contracting; $45,000 for TAT's extramural costs; and $15,000 for EPA's intramural costs. This memorandum will confirm your prior verbal authorization of Trust Fund monies, issued to the Chief, incident Response and Prevention Section on September 1, 1987, to initiate the removal action at the subject site, and subsequently revised to the current project ceiling of $100,000. II. BACKGROUND A. Historical Information A request for EPA analytical support for one well in the Tutu Section of St. Thomas was made verbally on July IS, 1987 from DPNR. On July 31, 1987, a verbal request for EPA to assume the role of Lead Agency was made, and this was followed bv a written confirmation of the request, dated August 10, 1987 (received by the Emergency and Remedial Response Division on August 19, 1987)* The initial request was based on a report that one well was reported to have a strong odor, characteris- tic of a petroleum product. This well is a major source of commercially orovided potable water for.the eastern portion of the island. IKPA's preliminary investigation commenced on July 21, 1987, witfc a field reconnaissance and sampling of this one well and six £44itional wells identified in the immediate area. Several of tfe£«* wells are also major water suppliers of public drinking wat«tfvt« the eastern part of the island. -3- Laboratory results from this survey indicated that the initial well was highly contaminated with gasoline and chlorinated organics, and the additional six wells contained elevated levels of chlorinated volatile organic compounds. Based on these results, DPNR declared that an imminent health threat existed, which could affect approximately 20,000 people living in St. Thomas. In addition, an indefinite number of tourists who vacation in St. Thomas were at risk since these commercial wells supply water to major hotels and restaurants. DPNR issued orders to close these seven commercial wells to protect public health. 'Subsequent to this action, EPA expanded their sampling plan due to the threat of greater contamination to drinking water wells in the area. EPA along with DPNR, identified other wells within the Tutu Water/Turpentine Run Aquifer which may be impacted by the hazardous substances identified to be pres- ent in the groundwater. A second round of groundwater well sampling took place on August 10 and 11, 1987, which included a total of twenty-four (24) wells identified in the Tutu Section of Anna's Retreat. All twenty—four wells were sampled and analyzed for volatile organic compounds. Following these results, DPNR closed the five private wells which- service two three-family hones and one apartment building housing twelve studio units. B. Site Setting/Description The contaminated wells are located in the Tutu Section of Anna's Retreat, St. Thomas, U.S. Virgin Islands. The five (5) private wells recently ordered closed are located in the Tutu residential area. At the present time, the affected area is not serviced by any public water supply. EPA sampled a total of twenty—four (24) wells in the Tutu area and found five private wells and eight (8) commercial wells seriously contaminated with up to 7,600 ppb of PCE. (See map attached). C. Quantity and Type of Substance Present EPA sampled Mp-. Analyzed for suspected volatile organic com- pounds on J«npl2 and August 10, 1987. Listed below are the maximum conc4pl&Btions of the hazardous substances identified in the drinking water wells: -4- Contaminant Tetrachloroethylene Trichloroethylene Maximum Concentration Found (ppb) 7,600 61 Statutory Source of Hazardous Substances under CERCLA Clean Water Act Section 307(a) Clean Water Act Section 307(a) Benzene 1,400 Clean Water Act Section 307(a) The results of the sampling are contained in Tables I and II. PCE contamination ranged from non-detectable to seven thousand- six hundred parts per billion (7,600 ppb). Sampling results adequately document 3 wells with contamination above EPA's 175 ppb PCE 10-Day Health Advisory Level and eight (8) wells above the DPNR's interim standards for maximum contaminant levels of volatile organic compounds in drinking water. III. THREAT A. Threat of Public Exposure Direct contact with PCE may cause eye and nose irritation along with dry scaly and fissured dermatitis. Acute exposure through absorption, inhalation or ingestion, may cause central nervous system depression, hepatic injury and anesthetic death. PCE has been found to be carcinogenic. This is a case of actual contamination in excess of the EPA 175 ppb PCE 10-Day Health Advisory Level for a three-family house and one apartment building housing twelve studio units. In the other three family apartment dwellings, the well con- tamination exceeded the interim DPMR drinking water standard of 50 ppb for any single volatile organic constituent. In addition to the exposure via consumption of the water, or eating food prepared with this water, showering with water contaminated with volatile organics can contaminate the air to significantly unhealthy levels. -5- The location, direction and dimensions of the plume are af- fected by variations in water table depth, rate of pumping of the wells, duration and intensity of rainfall, and inter- mittent releases of chemicals from one or more sources, all of which are unknown at this time. Given the above variables which affect contaminant strengths in any well within the plume may vary randomly. On September 2, 1987, DPNR issued three (3) orders to close wells and issued two (2) advisory letters to homeowners not to use well water for drinking, bathing and washing. B. Evidence of Extent of Release Investigation, sampling and analyses by EPA have identified contaminated groundwater, as described above, and containing contaminates, as described in Tables I and II. C. Previous Actions to Abate Threat No mitigative action was taken by any Potentially Responsible Party prior to EPA's recent activities. D. Current Actions to Abate Threat v EPA has commenced an investigation of the Tutu Water/Turpentine Run Aquifer by establishing a cooperative agreement with the U.S. Geologic Survey to define the characteristics of this aquifer and to determine the extent of contamination. EPA and DPNR have also completed Aquifer and a monthly well monitoring program is being developed. V DPNR has issued a total of ten (10) orders/advisories to well owners to close sixteen (16) wells. A local dry-cleaner has been identified as using and storing PCE. Handling, storage and disposal practices from this facility are unknown at this time. DPNR has proposed to issue an advisory to local dry cleaning establishments instructing them to properly store and hold all waste for proper disposal by an industrial waste hauler. VoPNR with the assistance of EPA is conducting an assessment of at least nine (9) facilities identified to b« potential sources of hazardous waste and/or substance releases in the Tutu area. -6- EPA has cleaned the homeowner's cisterns that have been contam- inated by hazardous substances from the groundwater, modified the existing home plumbing to terminate well connections, and intends to continue to deliver clean water via tank trucks on a regular basis, and establish a surveillance program for all wells in the area by a monthly groundwater monitoring program. This Phase I, short-term removal action will mitigate the threat to public health by providing a temporary alternate source of water for affected consumers. IV. ENFORCEMENT The contaminant plume is generally believed by both DPNR and EPA, to have its source from past and present improper handling and disposal practices of organic solvents, possibly from dry cleaners and auto repair shops operating in the area. This site has been referred to the Site Compliance Branch for enforcement action. An attorney and enforcement project officer have been assigned to this case. EPA issued Request for Information letters to all Potentially Responsible Parties. V. PROPOSED PROJECT A. objective of the Phase I Removal Action The primary objective of the Phase I of the removal action is the mitigation of the threat to public health by providing a safe potable water supply to the affected residences. Two three-family homes and one apartment complex housing twelve studio units were identified as being dependent on groundwater from their own private wells. Their respective wells were ordered closed-down by DPNR for exceeding interim drinking water standards. To reach the objective of providing a safe interim drinking water supply and protect the health of the public at risk, the following removal action was initiated. Hater storage cisterns, which received contaminated groundwater from affected wells, were cleaned and sanitized. Cisterns were filled with clean, safe, drinklag water. Water tank trucks from local water haul- ers will be providing water for the affected cisterns on a reg- ular basis. Plumbing modification was made to disconnect water lines from the contaminated wells which provide groundwater to the cisterns. -7- An attempt to connect well water directly to toilets for flush- ing will be made, if physically and economically feasible. A well surveillance program will be implemented involving all the wells in the Turpentine Run Aquifer, thru monthly sampling and monitoring. The longer term, Phase II objective will require the provision of a permanent alternate water supply in lieu of the temporary trucking of water to the threatened consumers within the plume area. Upon completion of an analysis of the alternatives for permanent water supply to these residences, a recommendation will be made for Phase II. B. Project Estimated Costs Water consumption per person per day on the average is thirty (30) gallons. it is estimated that the one apartment building /- has twelve studio units with the average of two people per unit. The two other private homes are three-family dwellings with the average of ten people in each. The cisterns in the three family houses are small and, therefore, a supply of water must be deliv- ered every two or three weeks, respectively. The delivery period is currently estimated to be one year or when a permanent alter- nate water supply can be provided, whichever occurs first. PROJECT COST (PHASE I) Cisterns Clean-Up; Provide labor, material and equipment including one vacuum truck, pressure water spray guns, water tank truck, etc., to drain and dispose contaminated water and to clean and sanitize identified cisterns....... $13,000 Modification of plumbing including Labor and Materials............................. $ 5,035 Refill cisterns with clean and safe drinking water........................................... $ 2,665 provide 64st*rns with clean and safe drinking water on regular basis according to a pre- approved schedule............................... $15,000 Contingency (10%)............................... $ 4,300 Total Mitigation Cost................. $40,000 -8- Extramural TAT Cost TAT Monitoring and sampling program (Including travel and per diem)................. $35,000 TAT Technical and administrative support (including travel and per diem}......... $10.000 Total TAT Cost $45,000 Intramural EPA Cost (Including travel and per diem)..................$15,000 ESTIMATED TOTAL PROJECT COST..........$100,000 This figure represents the estimated total for Phase I. It could be reduced significantly, if a reliable and permanent alternate water supply is found sooner than the proposed 52-weeks delivery period; might be increased, depending upon the identification of new drinking water wells found to be contaminated with hazardous substances within the affected area. C. Project Schedule Project initiation of cistern clean-up and safe water de- livery has already been implemented based on verbal funding authorization. Safe water delivery period is currently estimated not to exceed one year or when a permanent alternate water supply can be provided, whichever occurs first. V. RECOMMENDATIONS Conditions at the Tutu Well Site meet the requirements of Section 300.65 of the National Contingency Plan (NCP) for a CERCLA/SARA removal action. EPA has determined that there is a threat to public health at the site (Section 300.65(b)(1). This determination was based on: 1) RQS*n exposure to unacceptably high levels of acutely toftie substances (section 300 .65(b)(2)(i), and 2) Contamination of drinking water supply (Section 300.65 (b)(2)(ii) . TUT -9- The resident population at risk currently relies on well water as their source of potable water. pri va te This removal action complies with Section 104(b)(2) of CERCLA, as amended by SARA, in that it is consistent with the efficient performance of long-term remedial measures, by providing an interim supply of potable water to the public until a permanent water supply can be secured. This is a written confirmation of the initial and revised verbal approval of up to $100,000 for the total project ceiling estab- lished on September 1, 1987, by the Director of the Emergency and Remedial Response Division to the OSC for the CERCLA removal action at the Tutu Well Site. The mitigation contracting ceil- ing is estimated at $40,000, with an additional $45,000 for TAT costs, and $15,000 for EPA costs. Your authority to authorize these funds Administrator Alvin Aim's memorandum of is pursuant to Deputy Delegation Number 14-lA dated April R-ll-1200.6 15, 1984, of August APPROVAL: Dewling's Redelegation Order DATE: -TH DISAPPROVAL: DATE: cc: (after approval is obtained) C. Daggett, 2RA R. Salkie, 2ERR-DD S. Luftig, 2ERR G. Zachos, 2ERR-RP B. Sprague, 2ERR-RP J. Czapor, 2ERRD-SC G. Pavlou, 2ERRD-NYCRA J. Marshall, 2OEP P. Gelabert, 2CFO R. Gherardi, 20PM-FIN T. Sullivan, PM-214F (EXPRESS MAIL) T. Plaids, WH-548B P. McKechnie, 2IG TUT MO. r/21/87 r PHOTOVAC SAMPLING RESULTS TUTU WELL IITB 87. THOMAS, U.S. VIRGIN ISLANDS SANPLt LOCATION SANPLt DATE DATE VUXBf* fANPLtt ANALYZED SOURCE BEN TCI PCI TOL DCI CCHS HAXTMNAN CRUSH 07-473 07/22/07 HARTHNAN SAKER1T 07-474 07/22/07 4 IINOS VELLI1 07-475 07/22/07 4 VINOS VELLfI 07-471 07/22/07 TILLIT 07-477 07/22/07 flHA 07-470 07/22/07 E6LIN 07-470 07/22/07 TILLfT 07-400 07/22/07 FIELD BUUnC 07-401 07/22/07 07/30/07 II 07/30/07 IV 07/30/07 CV 07/30/07 CV 07/30/07 CV 07/30/07 IV 07/30/07 CV 07/30/07 CV 07/30/07 11 0 07 7 133 IS 3 «t*0 0 7 0 It It OSt11 711 0 102 3 (4 <1 200 4 31 SO 2040 41! 0 1 3 I 32* 1 ( .T .T f .T ) .T TABLE I HELL SAMPLING RESULTS TUTU NELL SITE ST. THOMAS, U.S. YXRGIM ISLANDS SAMPLE DATE DATE WI8ER SAMPLED AMALXED SOURCE BE* TCt PCI TOL DCt OCMS 4 flMOS II OOIA ffGLXM MELt 01 002* EGLXM IELL 02 003A EGLIN IELL 03 004A KARTHXAN IAKERY OOSA HARTHttA* CRUSH OOIA HAXTHMAI ESTATE 007A RODRICUE1 AUtO OOOA SRTAM 009A ALPHA,LEOMARO I10A SMITH.LUC1TA 01U OtVCOM 03 012A DEVCOi 01 013A 0101 OUA DEMITM 020A VXNA MILL 03 021A TIHA MILL 01 022A RAMffl 030A tTEEL 031A HARVET 032A MATHIAS 033A riANCOXS 034A OUCH 03U TILUT 03IA T1LUT OUf 037A flELO SLAMI 040A 00/10/07 00/13/07 CI 00/10/07 00/13/07 CM •0/10/07 00/13/07 CI 00/10/07 00/13/07 Of 00/10/07 00/13/07 XI 00/10/07 00/13/07 XI 00/10/07 00/13/07 It 00/10/07 00/13/07 XI 00/10/07 00/13/07 CI 00/10/07 00/13/07 Pi 01/10/07 00/13/07 Pi 00/10/07 00/13/07 Of •0/10/07 00/13/07 CI 00/10/07 00/13/07 MA 00/10/07 00/13/07 CI 00/10/07 00/13/07 XI 00/10/07 00/13/07 XI 00/10/07 00/13/07 XI 00/10/07 00/13/07 II 00/10/07 00/13/07 PI 00/10/07 00/13/17 It 00/10/07 00/13/07 PI 00/10/07 00/13/07 ft 00/10/07 00/13/07 CI 1301 00/10/07 00/13/07 CI 1401 00/10/07 00/13/07 MA 1 2] 11i: 11 i * 1! i H ( > ( > 24 1 i I 72 1 i 30 \ 43 i 07 3 31 1 1 0 1 120 0 00 2• 11 7 ) 270 i 7MO 1 II 1 120 1 0 1 240 •( I 120 3! 1 • ( L 213 13 71 II 1 1! 0 li 1 1! 14 1 144 4 1 174 1 124 1 4 1 1 1 i L I \ L . L . I . 1 . ) . 1 . i « 1 . ) . t P T TABLB XX 13. VIHA (,2-) 19. Lockhart 14. Leonardi.0 15. D.mitri 16. Dcnch 17. DevconO) 18. D«d« Hell Location Hap: 1. Bryansk) 7. Mathlas 0> 2. RodriguczO) 8. Smith Vi) 1. Harttman (3) 9. Francois >. Eglin 13) 10. Tillet 5. Harvvy lO 11. Ransey U 6. St««l« (,') 12. 4 Hinds f \ \ \\ REFERENCE NO. 16 U. S. Geological Survey Water Resources Division Caribbean District Open - File Report A SURVEY OF THE WATER RESOURCES OF ST. THOMAS VIRGIN ISLANDS I I UNITED STATES DEPARTMENT OF THE INTERIOR IN COOPERATION WITH THE GOVERNMENT OF THE VIRGIN ISLANDS OF THE UNITED STATES ABSTRACT St. Thomas, with an area of 32 square miles, is the second largest of the Virgin Islands of the United States. The island is mountainous, and slopes commonly exceed 35 degrees along a central ridge 800 to 1,200 feet high running the length of the island. The general appearance is a panorama of numerous steep interstream spurs and rounded peaks. The island is made up of rocks of Cretaceous age, mostly volcanic flows and breccias. A thin limestone and tuffaceous wacke complete the sequence of major rock types. All the rocks have been tilted and dip about 50 degrees north. Water in Charlotte Amalie, the capital, is supplied by sea-water desalting and water barged from Puerto Rico and is augmented by hillside rain catchments and individual roof catch- ments. Rainwater augmented by water hauling and a few wells is the source of water for the rural areas. Streamflow is meager—2 to 8 percent of the annual rainfall— and is predominantly storm runoff. Runoff after rainstorms seldom exceeds 5 percent of the rainfall. Runoff is rapid, however, and flash floods occasionally occur. Test drilling has shown that water can be obtained from fractured volcanic rocks in nearly all parts of the island. Wells will yield, generally, less than 1,000 gpd (gallons per day). In the upper Turpentine Run Valley and the Lovenlund Valley, short- term yields of individual wells are as great as 100 gallons per minute. Estimates of potential yield from these areas are 300,000 and 100,000 gpd, respectively. Two smaller areas—Long Bay and Lindberg Bay on the outskirts of Charlotte Amalie have estimated ground-¥M|pr yields of 70,000 and 30,000 gpd, respectively. Fully developed^* tbe surface- and ground-water resources of the island could yit$j$jt.3 million gallons of water per day. Ground water is slightly saline, commonly containing more than 1,000 milligrams per liter dissolved solids. The principal source of the minerals is bulk fallout of sea- and land-derived dust from the atmosphere. Solution of minerals from the rocks of the aquifers is the second largest contributor. Nitrate and some of the bicarbonate content of the water is probably derived from vegetation and animal and human wastes. Surface water is similar in mineral content to ground water during base flow. TUT 002 O: Caribbean District Open-File Report UNITED STATES DEPARTMENT OF THE INTERIOR Geological Survey A S U R V E Y OF THE W A T E R R E S O U R C E S OF S T . T H O M A S , V I R G I N I S L A N D S by D. G. Jordan and O. ]. Cosner Prepared in cooperation with the Government of the Virgin Islands of the United States 1 9 7 3 A S U R V E Y O F T H E W A T E R R E S O U R C E S O F S T . T H O M A S , V I R G I N I S L A N D S by D. G. Jordan and O. J. Cosner LOCATION AND GENERAL SETTING Location The Virgin Islands, forming part of the Antilles Island Arch separating the Caribbean Sea from the Atlantic Ocean, are about 1,400 miles southeast of New York and almost 1,000 miles east southeast of Miami. St. Thomas, the northwesternmost island, lies about 50 miles east of Puerto Rico (fig. 1). St. Thomas ts the second largest of the more than 50 islands and cays constituting the Virgin Islands of the United States. The island is approximately 14 miles long and 2 to 3 miles wide and has an area of 32 square miles. Lying within a few miles of the coast are nearly 40 smaller Islands, ranging in area from slightly less than a square mile to a few hundred square feet. ATLANTIC OCEAN .MMBAV C A R I B B E A N S E A Figure 1.—Location of the Virgin Islands of the United States.. Population Climate St. Thomas has about 17,000 permanent resi- dents and a transient population of tounst and im- ported laborers of about 8,000. The majority of the population is urban—about 20,000 people live in Charlotte Amalie, the only city and also the seat of government of the Virgin Islands. The permanent population is increasing rapidly and is expected to double by 1980 (unpublished data, V.I. Planning Board, 1964). Topography The land surface is almost entirely sloping and extends seaward from a central ridge, 800 to 1,200 feet high, running the length of the island. The slopes, which commonly exceed 35 degrees, are dissected by numerous stream courses of steep gradient. The general appearance is a panorama of steep mterstream spurs and rounded peaks. Flat land is confined to the Charlotte Amalie area and a few small alluvial-filled embayments. The only variation in the general topography is in the upper valley of Turpentine Run in eastern St. Thomas. The valley has relatively gentle topography consisting of rolling hills in a basin surrounded by steep slopes and sharp ridges. Land Cover and Use At one time almost all the land, including that characterized by steep slopes, was under cultiva- tion, primarily for grazing or growing sugarcane or cotton. Agriculture, however, has declined almost to extinction. A few square miles of land are still devoted to grazing in the eastern part of the island, and about 10 acres are used for truck gardening in the north central part. The remainder has been allowed to revert to brush and secondary forest. Now, land us* l«.efcinging rapidly, much of it brought on by the }4MM||| and its rapid mass trans- portation. IncreMM£pDpulatlon, in part caused by development of-JH^pod as a retirement haven and by tourism, r»Si&jt'fa more land being used for urban and suburban development. The increase in population not only makes new demands upon the water supply, but also the changes in land use could very well affect the available quantity and quality of the water resources. The average annual rainfall is about 45 inches and the average temperature is only 80°F, but the prevailing impression of the climate is one of dryness, especially in the winter. This is espe- cially true of the east end of the island, where, because of orographic effects, rainfall is only about 80 percent of that elsewhere. Rain is seasonal, nearly half falling between August and November. February and March are the driest months and September and October the wettest. Most of the rain occurs as short, intense showers lasting but a few minutes. Rains exceeding 1 inch, with accompanying overcast, cloudy skies, come but six or seven times a year. Thus, there are few days when the sun does not shine. Although major rains are rare, their volume is noteworthy. The greatest rainfall of record was 18.0 inches September 13-14, 1928, during a hurricane. The last great rain in recent years was 10.6 inches May 8, 1960 , the result of a stationary tropical depression. The island lies in the path of hurricanes and occasionally receives heavy rains and high winds from passing storms. The incidence of direct hits is low—damaging storms having a frequency of about one every 33 years. The last hurricane to cause extensive damage was in September 1928. The direct rays of the sun are very hot, but air temperature is modified by the almost constant trade wind. Air temperature (table 1) ranges from a mean low of 72 .0°F in February to a mean high of 87 .8° F in August. The highest daily temper- ature of record was 95°F and the low, 63°F. The prevailing wind direction is from the east. Northeast and southeast winds are relatively common, but west winds are rare. Monthly average wind velocity during 1953-58 at Harry S. Truman Airport is given in table 1. A wind rose for the same period is shown in figure 2. Relative humidity is high owing to the proximity of the sea. At Harry S. Truman Airport during 19S3-58 relative humidity was highest, averaging 81 percent,in the early morning hours, and lowest, averaging 66 percent, in the early afternoon. Average daily humidity is given in table 1. JT -(••29 ATLANTIC C E A N Gromlic rock* I I / I / l i t / I I I J ^"Yo / / / / / / / / V / I / / / I nr'i / / / / l / 1 l 7 }* \7^J. '.'. i. i. '. t. '. f ' ' ' ' > ' ' i ^•^^a^ I I / I I I / ruAPIATTC AUAI \F~T / / C~> CARIBBEAN SEA CO • 9*00' I S milt* • 4*99' Geology gtnefolutd oiler T W Donnclly, I960 64«SO' I EX PL A N A T I O N 0,6 E* 3s: ALLUVIUM-Silt, cloy, and thin, discontinuous beds of sand ond gravel. Includes beach sand. Estimated maximum thickness 50 ft TUTU FORMATION -Tuffaceous conglomeratic mixture derived from older rocks Contains some limestone, especially near the top Maximum thickness greater than 6,000 ft. OUTER BRASS LIMESTONE-Thin-bedded siliceous limestone and a few thin beds of tuff Estimated maximum thickness 600 ft. LOUISENHOJ FORMATION-Water-laid tuff, breccia, and a few thin beds of limestone Maximum thickness known 13,000 ft WATER ISLAND FORMATION-Lava flows, flow breccia, and water-laid tuff intruded by dikes and plugs Maximum thickness greater than 15,000 ft Contact Inferred fault, dotted where concealed Figure 3.--Geology of St. Thomas. Geology The general geology of St. Thomas (fig. 3 1 has been studied for many years, but only recently have the geologic formations been named and described ;n detail (Donnelly, 1960, 1966). The names of geologic formations used in this report are after Donnelly. The names have not been adopted by the U.S. Geological Survey. The volcanic and sedimentary rocks of St. Thomas are of Cretaceous (and older?) age. The oldest rocks, those of the Water Island Formation of Donnelly (1960) are predominantly lava flows and flow breccias deposited at great depth on the sea floor. Uplift and subareal erosion followed deposition. The LouisenhoJ Formation overlying the Water Island Formation was extruded from a volcanic center probably sited in what is now Pillsbury Sound between St. Thomas and St. John. Near the presumed location of the volcanic orifice the roclcs are mostly very coarse reworked cone debris. Farther from the orifice, coarse material lessens and tuffs predominate. Near the base of the LouisenhoJ Formation is a conglomerate composed chiefly of rock from the Water Island Formation. The Outer Brass Limestone was deposited on the flanks of the LouisenhoJ volcanic cone during a period of volcanic quiescence. It consists of 200 to 600 feet of thin-bedded graphitic slliclfied radlolarian limestone and a small amount of included tuffaceous material. The Tutu Formation, the youngest rock exposed on St. Thomas proper,is composed almost entirely of angular debris derived from the LouisenhoJ Formation and minor limestone debris from thin limestone deposited contemporaneously with the Tutu Formation. The rocks were subsequently tilted to form a northward-dipping horaocline. Dips range from 15 to 90 degrees and av*nv« about 50 degrees. Locally the formatt4Mi£ra overturned. The permeable 4&M* that these rocks once may have had after deposition have been destroyed by metamorphism or by deposition of minerals in pore spaces. Ground-water movement is now limited to openings along joints and fault zones. The homoclinal structure is cut by sets of faults trend- ing N 45°W, N 55° E and north. Three well- defined Joint sets parallel each of the major fault directions. The valleys of the island have similar trends and are apparently the result of selective erosion of rock weakened by faulting and jointing. Prime zones of ground-water availability, therefore, follow the valleys. Small alluvial deposits ranging from Pleistocene (?) to Holocene in age he in the valley of Turpentine Run in east-central St. Thomas and the larger coastal embayments. The alluvium of Turpentine Run lies in a narrow band seldom more than 200 feet in width along the stream. Maximum thickness of the alluvium is about 40 feet. Most of this alluvium, which is composed of silt, fine sand, and clay and contains discontinuous beds of sand and gravel 2 to 3 feet thick, lies in the Mt. Zion-Tutu area of the upper basin and in the narrow valley from Manendal to Mangrove Lagoon in the lower basin. The alluvium extends out under the lagoon near the mouth of Turpentine Run. Although composed pre- dominately of fine-grained material, the alluvium readily infiltrates streamflow when the ground- water level is below the base of the stream. As such, the alluvium forms a readily rechargeable aquifer, although it is of small extent and yield. Some coastal embayments headed by intermit- tent streams contain small deposits of alluvium similar to that of Turpentine Run. Maximum thickness of these deposits is estimated to be 50 feet, and their areal extent seldom is greater than a few acres (an exception being the Long Bay and Airport areas near Charlotte Amalie), Near the sea, the alluvium interfingers with calcareous sand and at times contains lenses of mangrove- swamp deposits. Therefore, the deposits are of minor significance as sources of water. OCCURRENCE AND MOVEMENT OF WATER Water moves through a cyclic pattern—the hydrologic cycle—in which there are three storage areas : the sea, the land, and the atmosphere. On the land, surface water and ground water depend on: (1) the amount, intensity, and areal extent of the rainstorms; ( 2 ) the slope of the land; ( 3) the moisture content of the soil and vegetal coven ( 4} the infiltration capacity of the soil and underlying rocks; and ( 5) the size. number, and interconnection of openings in the aquifer. Rainfall Rain is the only natural source of fresn water to replenish the water resources of the island. Rainfall is seasonal, -.v;th the rainy season in late summer and early fall and a secondary wet season usually in May. Nearly half the ram falls during August-November ( fig. 4t. Rams exceed- ing 1 inch in 24 hours come six or seven times a year. Four to 1 5 inches of ram falls in a 48-hour period about once every 2 years m large storms. These rams can occur in any montn but are more likely during the hurricane season (August- N'ovember) . About half the time annual rainfall is between 40 and 50 inches ( f i g . 5). Less tnan 10 percent of the time annual rainfall is less than 35 inches, which usually means a major deficiency during the normal wet season and drought. The cumulative departure from average and the 10-year running average of rainfall shown m figure 6 shows that at this time of writing (1967) the island may be entenng a period of deficient rain- fall. With the exception of a few years in the late 1940's and early 1950's, rainfall in the past 30 years has been below average. There has been a long-term decline of about 10 inches in annual rainfall since the peak of the surplus rainfall period in the early 1930's. The most severe droughts of record occurred in 1964 and 1967 , when but 27 and 24 inches of ram fell, respec- tively. Area! distribution of long-term rainfall, shown m figure 7 ( see letter "a "), is controlled by topo- graphy and the prevailing easterly to northeasterly winds. However, individual storms may or may not show the effects of orographic control or pre- vailing winds and the a real distribution of the storms can be very irrwjular ( f i g . 7—letters "b" to "f"). ;•• The soil zone over most of St. Thomas is not more than 1 foot thick. Where of sufficient thick- ness it has, however, the unique property of absorbing large volumes of water—as much as 12 inches m 24 hours ( R. Scott. SCS, oral commun., 1963) . Examination of the soil zone wnen dry shows it to be coarsely granular, owing to clump- ing of clay and silt particles. Prolonged satura- tion is necessary oefore the granules creak down. As a result, the soil r.as a r.igh permeaoihty until well saturated, but, once saturated, it becomes poorly permeable and retains water in tne pore spaces between particles and rejects any excess. 0 Dservaticr.s aurir.g rainstorms indicate t?.at the typical soil zone will aosorb aoout I mcnes of water before some water is rejected or moves to tne underlying oedrock. Fully saturated, trie soil will probably retain 3 inches ot water per toot of depth. The capacity of the soil to hold large volumes of water, together with infrequent rr.ajor rainstorms and a high evapotranspiration rate, seriously reduces ground-water recharge and storm runoff. Eva potra ns pira tion Most of the water trapped m the soil zone returns to the atmosphere by evaporation or tran- spiration by plants (evapotranspiration). On St. Thomas this process is active throughout the year, and 90 to 95 percent of the rainfall is returned to the atmosphere. The tendecy of the soil to granu- late is also conducive to evaporation. As water is evaporated from the surface of a saturated tight soil, the soil again becomes granular and exposes the soil at depth to the circulation of air. Con- sequently, further rapid evaporation of soil moisture results. Transpiration is a major means of water loss from the soil zone and also from the upper part of the aquifer, if the water table is near the land surface. Grasses and shallow-rooted plants can transpire water only from the upper few feet of the soil zone, but many kinds of trees, such as deep- rooted false tamarind, transpire water from depths of more than 20 feet. The effects of evapotranspiration may be seen m the channel of Bonne Resolution Gut below the gaging station. The gut flows in a predominantly bedrock channel a few feet wide for about 1, 500 feet before reaching the alluviated embayment at Dorothea Bay. Base flow of the stream, when less than l O . O O O g p d (gallons per day) , disappears in this reach. The loss is attributed principally to transpiration by the dense growth of brush and (0 (o) overage onnuol (b) March 25-26. 1963 (d) May 9-13, 1963 («) August 28-29. 1963 0 1 2 1 4 9 MILES (0 Dtcerober 10-13. 1965 Figure 7 .—Isohyetals in inches of the long-term distribution of rainfall (a ) and of individual rainstorms (b-f) on St. Thomas. trees bordering the stream, from tne appearance of the vegetation in a dry period, only the vegeta- tion in a strip about 100 feet wide with a total area of about 3 acres benefits from the stream. A minimum water loss of 10, 000 gpd, 3. 6 million gallons annuallv, would indicate an evaootranspi- ration rate of 1.2 million qallor.s cer acre per year, or 44 incnes. Bowden t 1968 ) computed monthly potential evaporation ana soil-moisture deficiency at six stations on St. Croix using the method devised by C. '.V. Thornthwaite. Potential evaporation ranged from 58 to 69 inches and averaged 62 inches per /ear. Actual evapotranspiration (denved from potential evapotranspiration and change in soil moisture) ranged from 41 to 46 inches and averaged 43 inches per year. Bowden's data shows a soil- moisture deficiency 9 to 11 months of the year at the different stations. Surplus soil moisture occurred only in the months of Septemoer to November. The authors believe that conditions are similar in St. Thomas. Streamflow The 5 to 10 percent of rainfall not returned to the atmosphere by evapotranspiration from the soil zone either recharges the ground-water reservoir or runs off to the sea. Annual runoff in a time of average rainfall ranges from about 2 to 8 percent of the rainfall. Most stream channels on St. Thomas are dry and carry only storm runoff. Only two streams on the island have perennial reaches. In these reaches, about one-half to three-fourths of the flow is storm runoff, and the remainder is base flow (ground- water outflow to the streams ). From 0.5 to 2 inches of water annually reaches the sea as storm runoff. The amount of storm run- off varies from basin to basin, depending upon topography, soil mofcttur*, exposure, and vegeta- tion. Base flow ol t*j» streams with perennial reaches , while ofHfffjfc$B»l in volume to storm run- off, seldom reacn*J&l|fR.,sea• The flow usually infiltrates into alltffMftttposits in the lower reaches of the stream*! Ground Water From 0.5 men to as much as 5 inches of the rainfall annually infiltrates the sou and rocks to reach the ground-water reservoir. '.Vater in the ground-water reservoir or aquu'er moves by gravity toward the sea. '.Vhere the water taole is intercepted by the land surface, -.vater is dis- charged as a spring or as case tlow tc a stream. 'A'here it is near the land surface, =ucn as along stream cnannels and :n coastal ernbayments , large volumes of water are trar.spirea by plants whose roots tap the ground-water reservoir. The transpiration by plants directly :rcm the water table is so great that only minute quantities of ground water ever reach tne sea, oitrier as stream- flow or as seepage directly t.-.rougn tne so.l and rocks. fresh- Salt-Water interface fresh water in the aquifers Mono :ne coast is m contact with salt water in a dynamic £/3tem. So long as water levels grade seawara , fresh water will discharge to the sea at the snore. During times of ground-water recharge, the fresh- water lens thickens, displacing the underlying, heavier, salt water downward and seaward. Dur- ing times of no recharge, the fresh-water lens thins, as ground water discharges to sea. Salt water, which moves into the normally fresh zone :t water during times of no recharge, is not entirely flushed out by fresh water when recharge occurs. Some remains behind, where it mixes with mfluxing fresh water. The interface zone of brackish water is thick where fluctuations in the size of the fresh-water lens are large. In some coastal areas, where the fresh-water lens is thin because of lack of rainfall or unfavor- able topographic or geologic factors, the under- lying interface zone may extend inland several hundred feet at depths of but a few feet below the water table. The balance between salt water and fresh water in coastal aquifers is delicate and can easily be disrupted by man's quest for water. Salt-water encroachment can readily result by removing more water from the fresh-water lens than is being replaced by recharge or by pumping a well at an excessive rate, in which case the fresh-water head is lowered, and movement of salt water upward or horizontally into the fresh-water zone is induced. 10 TUT 002 0192 '.VATER SOURCES Fresh water has always Seen in critical supply in St. Thomas. Rain collected en roofs ar.d stored in cisterns is still the source of water for most rural ana uroan domestic supplies. 2efore 1960 r.illside rain catchments and a few dug v/eils were the major source of water for puolic supplies. Since then, desalted water nas oecome tne major source of water for public supplies, and water carged from Puerto Rico is a close second. Charlotte Amahe Charlotte Amahe nas a aual public water system. Fresh water is used for drinking and general house- hold needs, and saltwater is used for sanitary and fire-control purposes. The fresh-water supply, obtained from salt-water distillation plants, hill- side rain catchments, and a well, is supplemented by water barged from Puerto Rico. Potable water use and the sources of the water in figure 8 not only show the increasing demand for water but also the shift in sources of the water. In the late 1950's, with the exception of 1957, a drought year, catchments were the major source of water. Barged water became the major source of supplv in the early 1960's, but by the late 1960's, desalted water became the principal source of supply. Nearly all buildinos , both private and public, in Charlotte Amalie have roof catchments and cisterns. In 1926, before the establishment of a public water system, about 200 private and 17 public dug wells were in use in the urban area. Since then most of the wells have been abandoned because of sewage and salt-water contamination. Some of the salty water was drawn into the wells from the sea as a result of overpumping, and some of it entered the wells from leaky salt-water pipes. .'-i few of the wells are still pumped occasionally for nondrmking domestic supplies and for construc- tion purposes. In recent years, wells have oeen dug in eastern ChartOtt* Amahe for a supplemental •.•/ater supply for tUtfftptO1 public -housing projects. Several other wells^ngrf been dug in the same general area for w*^j^for nondnnking domestic use. Since 1926, 18 public hillside ram catchments have been constructed. Of these, 14 are con- nected to the urban water-distribution system. '.Vater is hauled from the remaining four catch- ments by individual users or by water haulers. The total area of the public catchments is esti- mate a to oe 24 acres, and the storage is estimated :o be 14 million gallons. Reliable figures are not available or. the amount of water used from any of the catcn.T.ems, but total yield is estimated to be 50,000 gpd. In addition to the public catchments, four privately owned catchments are in the urban area. A gallery well at the airport was an important source of v/ater in the 1950's. ;t reoortedly yielded 13,000 gpd. An attempt to increase pro- duction resulted in salt-water encroachment, ruining the well as a source of potable v/ater. in 1962 the first desalting plant, with a capa- city of 2 5 0 , 0 0 0 gpd, was put into production. In 1966 a plant of 1 million gpd was put into produc- tion, and, by 1967 , the start was made on a 2.5 million gpd desalting plant. The demand for water has increased six-fold since 1960 and shows little indication of leveling off. In 1962 and again in 1966, when desalting plants were put on line, water demand increased almost overnight to absorb the increase in produc- tion. Water barging, considered a stopgap measure, has had to be continued to meet the demand. The desalting plants reportedly will produce water at an average cost of about SI .00 per 1,000 gallons when operating at maximum efficiency. The cost of barged water from Puerto Rico depends upon equipment used, but in 1967 averaged about 53.50 per 1,000 gallons. Water is sold to the consumer at a cost of 50 cents per ton, about S2.00 per 1,000 aaii^ns. The difference between pro- duction cost and delivery cost is absorbed by the Virgin Islands Government. Rural St. Thomas Rooftop catchments and cisterns are still the r.ajor source of v/ater for rural St. Thomas. Dur- .ng prolonged dry penods, rainwater is supple- -ented by water hauled from public-supply points .n Charlotte Amalie. Small ponds have been con- structed, tapping storm runoff for irrigation water :or truck gardening and drinking water for stock. Since 1962 several private wells have been drilled 11 TO'1 ?bservations indicate that wind velocity ana roof configuration are major factors in the recovery -I rainfall from residential structures. High wind will blow ram off a pitched roof oriented parallel to the wind, whereas a rain shadow in proportion to the degree of roof pitch will occur on the lee = iae of a roof oriented perpendicular to the wind. A Y-snaped roof will be affected in the same .r.anner, iithougr. probably to a lesser degree. The ~ost eificient is probably a flat roof with a low lip :r:;una trie edge. Water cannot blow or: the root", nor :s a rain snadow created, and the lip converts tr.e roof into a temporary storage container during high-intensity rams. Rainfall recovery on flat roofs is probably greater than that measured from the nillside catchments, whereas recovery on pitch roots :s probably 10 to 20 percent less , depending ^n orientation and steepness of pitcn. Figure 25 shows an estimate of the annual costs of collecting rainwater and of cistern storage tor a small home. Cistern cost, amortized over a 20- year period at 5 percent per year (interest costs not included), is estimated to range from ?5.00 per cuoic foot for 10 percent storage to ;2.50 per cubic foot for 100 percent storage of the total annual recovered rainfall. Rainfall recovery was estimated to oe 70 oercent of an annual rainfall jf 40 mcnes over 1 , 000 square feet of roof, -e- covery unaer tnese conditions would yield 48 gpd :t was assumed that water loss due to insufficient storage would oe maae up oy water purcnasea from water haulers at costs of 10, 20, or 30 dollars p«r 1,000 gallons. The figure shows that, using these critena, the optimum cistern storage would be about 20 percent of expected annual recovery, or about 3.5 gallons per square foot of catchment. Average yield from rainfall alone would be about -iO gpd. Annual water cost would range from $130 to SI 96 annually, or S7 ,-15 per 1 ,000 gallons to ill .20 per 1, 000 gallons. Annual cost of 100 percent cistern storage would be $294 or SI6.80 per 1 , 000 gallons . Ground Water Ground water is available in nearly all parts of the island in sufficient quantity to be of impor- tance to the water supply. :n general, yields of wells are sufficient only for individual domestic supplies. There are, however, a few areas where yields to wells are large enough to warrant 500 400 <=> 300 too 1 200 100 I I Supplement voter 130 per 1000 gallons Storage |5 gallons per squarei footl (28 percent) ; | Supplement water 120 per 1000 gallon's per sruore foot (58 percent) Supplement water «10 per 1000 ballons 10 80 90 100 20 30 40 50 CISTERN STORAGE. IN PERCENT OF TOTAL CATCH Figure 25.—Annual cost of water from a roof catchment of 1,000 square feet with a maximum yield of 48 gallons per day. 31 "LIT 0194 Taoie - 4 . - -Scale .;: vaiues ;or determining ground-water potenual from physical criteria ana examples for selected wells Rainr'au Inches | Value < -10 ' 0 1 1 40-45 ! 1 45-50 • I \ > 50 ' 3 ! i I Topoqrapny Crest of ridge General slope Central valley on general slope Large valley or. alluvial flat Value ,i 1 [ 2 i 3 1 Cxcosure North or south _;lope South slope North slope Sheltered interior valley Value 0 1 2 2 Drainage area -c.res <100 101-200 201-300 301-400 >400 Value 1 2 4 6 8 Potential Sum of values 4 or less 5-6 7-8 9-10 11 or greater Long term yield , ^pd <500 500-1,000 1,000-5.000 5,000-10,000 10,000 + Examples Well 3 Well 10 Well 22 Well 20 Well 16 2 1 1 1 1 2 1 2 3 4 2 1 2 2 2 1 1 2 6 6 7 4 7 12 13 1,000-5,000 500 1,000-5,000 10,000 10,000 32 TUT the development of public supplies for local use. The water, as a whole, is oi poor quality, being slightly mineralized, but can still be considered potaole. '.-. -or. oe blended vmn cistern water, yielding a mixed water of more acceptable pota- bility. Kousenolders wno nave wells generally prefer a dual system, using the -.veil water for washing, lawn watering , i.-.d sanitary purposes and r a i n w a t e r for d rink in•: inc. no-'-ing. jround-'A'atei P o t e n t i a l "K" -nin^-i-water poter.tiol A an iroj can in large part be determined by ^ne av<=r- ^ - ^ n u a l r a i n f a l l , topogrnpny, and exposure to sjlar ra::ia- tion. 'n general, areas receiving l>_-ss :nan -tu .nches of rainfall have a lew ground-w.iter c-ten- tial. The southern slopes of the island, .mere, because of solar radiation, evapocranspiration :s nigh and recharge is low, generally have less ground-water potential and yield more nighly min- eralized water than the north slopes. Topography is important in th-i' - th" flatter slopes ground- water recharge is favored. A crude scale based on rainfall, topography, exposure, and drainage-basin area was developed for estimating yround-water potential of the rocks of the island (table -i) . The different features are assigned values ranging from 0 to 8. The sum of these values is a number from which an estimate of the lone-term vield of a well can be obtained. A deep well will generally yield more water than a shallow well in the same location. For the purpose of the scale, a well depth of about 200 feet is assumed with the water level in the well at 50 feet below land surface. Little water is yielded from depths of more than 200 feet below the water table. It is emphasized that even though conditions appear favorable foe obtaining o ground-water supply, there is 0$tfpys a possibility no water will be obtained as 4 l)|J|j£jnay not penetrate water- bearing strata. Water in Consolidated Rocks The permeable zones ot cue consoliri-torl rncks consist of open joints and fractures. Xear the land surface the joints are open—the result of weathering and release of pressure. Joint open- ings, however, narrow rapidly with depth, and generally at depths of a few hundred feet they are too narrow to transmit significant quantities of water. All the bedrock formations are broken by faults-- fractures along wruch movement njs taken dace . In some faults, earth movement has crushed tr.e rock to gravel-size oreccia, whereas in ethers the rock has oeen reduced co a flourlike suostance called fault gouge. Brecciated fault zones not sealed by mineral deposits or fault gouge car. oe very permeable and often extend to depths of hundreds of feet. The orientation of many of the valleys ana bays •?videntl/ is controlled by a fault and joint system along which erosion has occurred, .'alleys, therefore, are often indicators of zones of an extensive jointing or fracturing system that may contain ground water. The yield to .'/ells drilled in the bedrock is small—generally less than 1,000 gpd. Many wells will yield 5 to 10 gpm (gallons per minute > for about 10 hours. After that they yield at a much reduced rate as a result of removal of water from storage in the immediate vicinity of the well. Once water in local storage is removed, the yield to the well is reduced to the general yield of the aquifer. For example, well 17 near Wintberg re- portedly yielded 12 gpm (17 ,000 gpd) for a 24- hour pumping period when first drilled. However, almost daily use over the past 5 years has shown that the long-term yield of the well is about 250 ja lions per day. The consolidated rocks are permeable as a result of interconnected open fractures along joints and faults, which tend to be linear. How- ever, permeability may vary significantly along a hneation. One example of possible linear permeaoility is the north-south fault in eastern Charlotte Amahe. Permeability, as determined from pumping tests of wells, ranged from about 1 to 9 gpd per ft2 (gallons per day per square foot) east and west of the fault. Immediately along the fault zone in the vicinity of the race track, however, permeability ranged from about 70 to 150 gpd per ft2 . South- ward along the fault permeability was 1 gpd per ft . 33 The effective porosity, or storage capacity, of the consolidated rock also is related to open inter- connected fractures and Joints. Effective porosity in the upper Turpentine Run basin is estimated to be 4 percent based upon changes in the ground- water level in response to rainfall. Effective porosity of the rocks in most of the island is esti- mated to be 1 percent or less . Water in Unconsolidated Rock Water-bearing unconsolldated deposits are present only in Turpentine Run Valley and in coastal embayments. These deposits consist of two dif- ferent llthologic types, which have a variety of water-bearing characteristics. They can be divided into (1) a bouldery silt and clay alluvium, which contains lenses and beds of sand and gravel, and (2) beach deposits, predominantly coral sand and occasional interbedded zones of coral, beach rock, and organic silt and clay. In the coastal embay- ments, alluvial and beach deposits may Interflnger. The alluvial deposits are predominantly fine grained, and, although they have a high porosity, they have a low permeability and will yield water only slowly to wells. Water in these deposits is with few exceptions underwater-table conditions. Sand and gravel beds and lenses In the alluvium are rare. Where present, however, they will yield water readily and act as a large collector system Into which water from the less permeable alluvium will percolate. Occasionally the water In the sand and gravel beds Is under artesian pressure because they are confined by the less permeable overlying alluvium. The beach deposits, principally medium to coarse coral sand, have a moderate to high per- meability and porosity and will yield water readily to wells. The moderate to high permeability of the beach deposits Is often detrimental in that salt- water encroachment can easily occur. We Ground water in Stv^HpMi is assumed to be underwater-table coa0$Hbft»--that Is, the water surface is unconflned, open to the atmosphere, and free to rise and fall. Sufficient data are not avail- able to show contours of the surface of the water table throughout the Island. In general, the water table roughly parallels the topography. The depth to the water table is a few feet below land surface in the coastal embayments but may be as much as 120 feet below land surface near the crest of the central ridge. The water table responds to changes in the quantity cf water stored m the ground-water reser- voirs. The water table rises when recharge from rainfall or streamflow exceeds the discharge; it declines when discharge to springs, streams, or the sea, evapotranspiration from the water table, and withdrawal of water from wells exceed recharge. Water-table fluctuations The hydrograph of well 1 in figure 26 is typical of the water-level fluctuations in the rock aquifer of the south coast. Recharge follows the infre- quent heavy rainstorm or smaller storms in a wet period. The overall low storage capacity of the rock causes a rapid rise in water levels, but the steep hydraulic gradients result in rapid losses and almost as rapid declines. Figure 27 is the hydrograph of well 24 tapping the alluvium and weathered bedrock in the lower Turpentine Run Valley, and figure 26 is the hydro- graph of well 21 In the alluvium of the upper basin. Recharge Is received every time storm water runs off In the stream and water levels rise. Between times of storm runoff, ground-water levels are partly maintained by the infiltration of base flow from the stream when flow is present. The hydrograph of well 19 in figure 29 shows the pattern of water-level fluctuations of the rock aquifer in upper Turpentine Run basin. The pattern is similar to that of the rock aquifer of the north coast and larger valleys on the south coast. Here, greater permeability and storage capacity and generally thicker soil and alluvium result In a slower but more prolonged response to recharge and a slower discharge. The "troughs" in the hydrograph during early 1965 were caused by pump- age (averaging 18,000 gpd) from a nearby well. Recharge The bedrock aquifer is principally recharged by infiltration of rain on the land surface. Stream- flow and storm runoff locally recharge the alluvium, which may, In turn, contribute water to the bedrock aquifer In the major valleys and allu- viated coastal embayments. 34 Rainfall, vegetation, evaporation, surficial deposits, and exposure to solar radiation are the main factors affecting recharge to the aquifers. Leaky-salt water and sewage mains in Charlotte Amahe and effluent from sewage plants in the Turpentine Run basin also contribute water to the aquifers as does effluent from septic tanks through- out the island. Recharge from these sources is detrimental as it is a potential source of pollution. The bedrock aquifer is recharged infrequently and only after a heavy rain or series of lesser rains. The amount depends on the antecedent rainfall and the degree to which soil moisture has been depleted by evapotranspiration since the last rain. Extensive brush cover and the granular nature of the soil cause rapid evapo transpiration. Conversely, the granular nature of the soil will allow water to pass through the soil zone without the soil being completely saturated—saturation being required only along the conduits between the soil granules. This reduces the water needed to satisfy soil-moisture requirements before recharge can take place. Even then, under dry conditions, a major rainstorm of 2 inches or more, or the equi- valent in lesser rains, is necessary to initiate re- charge to the bedrock aquifer. The amount of rainfall necessary for recharge varies from one part of the island to another. On the north slope 1 inch of rain may cause recharge, whereas on the south slope, under dry conditions, 3 inches or more may be necessary for recharge. The fluctuation of ground-water levels indicates that recharge to the aquifers on the south-facing slopes is less frequent than on the north-facing slopes. Less frequent recharge on the south slopes is attributed to the greater solar radiation received by these slopes, which results in increased evapo- transpiration and a greater soil-moisture deficiency. Consequently, a greater volume of water is neces- sary to overcome the soil-moisture deficiency before recharge takes place. Where the suriM|i$ deposits (saprolite or alluvium) are thicttj^Mtffing from 2 to IS feet, as on the north slope in I^WpCtnity of Dorothea , in upper Turpentine Run basw^and In the alluvial embay- ments, such as at Long Bay and the Harry S. Truman Airport, water is retained in the surficial deposits and takes a much longer time to reach the bedrock aquifer. Peak recharge to the bedrock aquifer may lag as much as a month behind the rainfall. In some places little recharge reaches the bedrock aquifer—as most is discharged to springs or streams directly from the saprolite or alluvium, as has been observed in the vicinity of Dorothea on the north slope. Runoff from major rainstorms is the principal recharge to the aquifers of the coastal embayments and is an important source of recharge to the alluvium of Turpentine Run. Base flow of Turpen- tine Run and Bonne Resolution Gut at Dorothea Bay, when present, also contributes recharge to the unconsohdated aquifers in their respective basins. For convenience of discussion, the island has been divided into five ground-water areas as shown in figure 30. Estimates of yield in these areas are given in table 5. Table 5. --Estimated yield of ground-water areas . >5e«d<j. 3u I .,,-ound -water irea 1 1 ( Lonq 3ayl 1 1 Lindberq Bay > 2 2 Upper Dasin 2 Lower oasin- 3 •1 5 Total Area , 3q ml 13.6 .3 I/ .2 I/ 3.4 2 . 3 1.1 •4.6 .42/ 10.0 32 estimated yieid •Jpd 450,000 70,000 y 30,000 3/ 350,000 300,000 4/ 50,000 !/ 250.000 100.000 100.000 1,250.000 mq/yr 164 25 11 128 no 18 91 36 36 -155 Annual recnarge. .nches 0.7 4.9 4.3 2.2 2.8 1.1 1.2 5.3 .2 I/ Approximate area of alluvium only. 2/ Does not include drainage baf ins at Areas 1 and 5 which contribute racrtarqe to Area 4 from surface- •vater runoff. j/ V:eld included in Area 1 total. 4/ Yield included in Area 2 total. Ground-Water Areas Area 1 Area 1 encompasses about half the land area. It is underlain principally by fractured volcanic tuff and breccia of the LouisenhoJ Formation, on which 1 or 2 feet of soil have developed. On the south side of the island, from the vicinity of Charlotte A ma lie westward to Brewers Bay, the volcanic rock has been extensively fractured. The fractures, however, have been filled with 37 ATLANTIC OCEAN E X P L A N A T I O N FOft SYMBOLS A Surface-water gaging station •' Drilled well, number refered to in text. O Dug well _ Gallery 94 Spring, number refered to in text. | Rain gage Kv--r>-J Pollution from salt-water mains l!!!i!i!i!i!!!i| Encroachment by sea water ------ Boundary of area C'..'.'•'• Alluvial deposits 2 Areas, see explanation below • 9*OO' _______________i________ I ^ tl V " « ^4 * ~S ( ^ IK 9~--—:^ yWi ^ ? - <y CARIBBEAN SEA IS'Zff 3 milt* *4*S3' COto E X P L A N A T I O N Are d Wells in rock 50 to 300 feet in depth will yield up to 1 ,000 gpd. In some larger basins and alluviated embayments yields up to 10,000 gpd may be possible. Water contains 1,000 to 1,500 my/1 chloride. Wells drilled near the sea and below sea level may yield brackish water when drilled or if pumped at excessive rates. Area 2 Wells in rock 50 to 250 feet in depth will yield up to 30,000 gpd. Generally, deeper wells have a higher yield. Short-term yields of selected wells may be as great as 150,000 gpd. Wells tapping alluvium of lower Turpentine Run will yield up to 10,000 gpd. Water contains about 1 ,000 mg/1 dissolved solids and about 200 mg/1 chloride. Little danger of salt-water encroachment except in lower Turpentine Run. Area 3 Wells in rock 5U to 200 (cut in depth will yield up to 5,000 gpd. In some larger drainage basins, yields up to 10,000 gpd may be possible. Water contains about 1,000 mg/1 dissolved solids and about 200 my/1 chloride. Wells drilled near the sea and below sea level may yield brackish water when drilled or if (jumped at excessive rates. Area 4 Wells in limestone 50 to 150 feet in depth will yield up to 50,000 ypd. Short-term yields of selected wells may be as great as 15n,000 gpd. Water contains about 1,500 mg/1 dissolved solids and 200 to 300 my/1 chloride. Wells drilled near the sea or below sea level may yield brackish water when drilled or if pumped at excessive rates. Area 5 Wells in rock 50 to 300 feet in depth will yield up to 1,000 gpd. In general yields are small. Water contains 1,000 to 1,500 my/1 dissolved solids and 300 to 500 mg/1 chloride. Wells drilled on penin- sulas and in coastal areas generally will encounter brackish water. Ground water polluted by leaky salt-water mains in Charlotte Amalie area. Figure 30.--Ground-water areas of St. Thomas showing location of wells, springs, stream gages, and rain gages. secondary minerals. Alluvium and beach deposits fill the coastal embayments and are especially prominent in the Charlotte Amalie area. Ground-water levels range from a few feet below land surface in the embayments near the sea to as much as 120 feet below land surface on the central ridge. Depth to the water table is greatest beneath ndges and least in the valleys and lowlands. Wells range in depth from 50 feet in the low coastal areas to 250 feet or more near the central ridge. In general, the higher the altitude of the well site the greater the depth of the well. There is really no particular depth at which an aquifer can be successfully tapped, as yield depends entirely on the depth and density of open water-bearing frac- tures. A well in the Long Bay area (well 12) at an altitude of 40 feet was drilled to a depth of 120 feet before water-bearing fractures were penetrated. Well 10, on the other hand, at an altitude of 320 feet on the slope of the central ridge, penetrated water-bearing fractures at 60 feet. These, of course, are extremes. Long-term yields of wells generally range from 250 to 1,000 gpd, although initial or short-term yields may be 10 times greater. Two valley areas. Long Bay and Lindberg Bay on the east and west edge of Charlotte Amalie, re- spectively, have greater ground-water potential tha n the remainder of Area 1. Long Bay. —The Long Bay area lies in a basin about 1 square mile In extent, of which about 0.3 square mile is alluvia ted coastal embay ment, and the remainder is steep-sloped volcanic ridges with little soil cover. Alluvium as thick as 60 feet overlies the bedrock. Near the coast the alluvium underlies and interfingers with a thin beach-sand deposit. A relatively Impervious clay overlies the bedrock from a line about 1,500 feet inland sea- ward to the shoreline at Long Bay, and probably extends out under LadfcjkjMr. Water is present in the alluvial deposit*,flu the main aquifer is the underlying volcanic FQBlt. In general, the bedrock underlying the alluvMMpfteldl more water than that underlying the ridges. The zone of greatest yield co wells is oound by the two faints passing : .ir; •_,-.-. r.he area. A factor c:jr.:r:bi:'.:.-.; to tr.e :;rcauct;v:ty -f •.-!•: bedrock is trie ovorivi.-iq alluvium that acts ^i j storage res^r/cir. T!te alluvion <: ?r.tj::-.s . ;-^-2 Tuar.tiUes jf v.'v.sr. T^causa cf :ts 1 .w Lemea- bility it generally yields little water 'o -.veils, but it yields water sicv/ly to tne ^.-.aerlv:.-.-; cod- rock aquifer. The principal area jf rec.-.-r;e :,: the bedrock aquifer trorn rhe alluviurr. : : t ::.-.> foot of the volcanic riatjes inland :t ..-. ? -:^--e •: the impervious clay wedge capping tr.-j ~-»:r^c.-: and mostly upgradient from the area ><i '02/••.•/ .:- water mains. The long-term yield cf the ailuviutr.-",edrcc'< aquifer is estimated tc be from 60,00.) --> '-.> ;00 jpd. The yield of wells ranges tr?m ar:ut ; : 0 to 70, 000 gpd. The high yield of seme or th? wells, however, has little to do with tre !•_:-:- term yield of the aquifer. Sustainec p^mpaca .r. excess of the long-term yield of the aquifer wnl deplete the fresh ground water in storage and prob- ably result in salt-water encroachment. Salt water has encroached in a narrow strip cf the alluvial aquifer bordering Long Bay because of pumping dug wells 13, 14, and 15, which supply Pear son Gardens public housing. Nearly half the alluvial aquifer, however, is contaminated to some degree by leaky salt-water mains. The approximate limits of salt-water contamination are shown in figure 30. The bedrock aquifer under- lying most of the contaminated alluvium contains freshwater because the principal recharge area is upgradient of the relatively Impermeable clay cap overlying the bedrock throughout most of the contaminated areas. Salt water has entered the bedrock in at least one place. Well 11 became salty after being pumped heavily for about 3 months. Salt water from the alluvium has apparently entered the bed- rock aquifer through several improperly construc- ted v/ells. In each the annular space between the //all of the well and the casing was left open, and salt water moved down the annular space, contam- inating the bedrock aquifer in the vicinity of the well. 40 -?r/ simlcr ~.c .r •: •?1 basin are* : ./men is ;:: •-.-. :s r.r.i-->. :ge ar.c • • v :. - ••/"Us in 're - / . ,-.•/ per:--iioilif.-. : ..-v;.;r 13 ~r: nariv - .-• -.i.cari.-ir.j T3ircc< i j . --.jjr.u .-.roccia 3--. :u:f. ~ ic;'. :: -.,: altered oy -33: :.":- intrusions. ' T •> :'. • •'-. jv_ir!iv.: .J rxter.ii'. •» .'-..: T.C.'V :f the ::: j:. .-2S ..e ullsu v/ich :•:••_ ,.- ..ir' r. .••..•:-e '.v-'ils, ;. c. 3i-.c . . . < -^ ~een arilieu in •-.e o-^r;c.-. 3*0.-.; :,-.» v.rc=r •:•'-;? ?i the ailuvidi .'pos.Cj. .'eii ," j j dry. -.'.''~'j-j.n. '-t v.'js '".r'.ilod :: i -ir-i-cn of 2'JO f-eet. '.'.'-:'..-: -, :ij o nave : .:•,-.3- :5rr, ".-'Id. liscma'.e'i to bo ,,i< /O opd. 3e^.rcc!< ••ei'.i r.robabiy •vili yield i.1,^1.1; qpd in the cer.-_--i "Tt .'. i-.e er.baymen: t.ortr, cf the airport. T/.e ni_. :•_:.-. •<= relati'/aiv :hic'. :here 3nd, tr.us, .' ;ho'iiu contrioute 'jon.•jia^'sbts su.intities c: w a f e r T3 -.hi 'ji-jerlving oedroc< .'j.Tuifor. r .j potential yield of the bedrock aquifer .3 •• -•!.•: -v.-) r.c oe 30,000 gpd, assuming djta -ctaiiet •r*r. -,..j Lung 3ay ar^a car. ce applied. Salt-water mains in the Bourne Field housing jrsa are known to leak, and it must be assumed ;:-.jt tr-.a 'jlluvium in that vicinity is contaminated. The same care to prevent salt-water contamination •jy ir.croper well construction must be taken nere •is in che Long 3ay area. At one time a gallery paralleling the runway 3t the jirport wf^HMd for water supply. This gallery, which <jjMHM3 runoff from the runway =)r.d stored w3t«NH9M'Alluvium and landfill fir future a3e, .-.ad tMpB^atiinated to be 11,000 gpd. U-fortunately, tH> utfeiy im in overpumped ?nd salt-water encroachment followed. Salt water is sail present in the alluvium near the well and is .r. a position to intrude the bedrock aquifer. .Vater from the gallery occasionally is used for ~~r:able purposes. The use of water from •V.-.-Q-.'drainage for drinking purposes, of course, because of the presence of toxic such as Hydrocarbons and tetraethyl frum spilled aircraft fuels. 'rea 2 is the drainage basin of Turpentine Run. ;r.'/enience it is separated into an upper ana •-c Lasin; the upper basin above the stream- i-. j -:tation near Mt. Z;on, and the lower basin ."••• ;:. The principal rocks are volcanic flows, :d breccia. Alluvium as thick as 40 feet :ne main stream channel of the lower oasm. r'/est-onented fractured and jointed zone )tnermally altered rock bisects the upper ?r.i:?d wells range from 40 to 250 feet in isrcth. The shallower wells tap the alluvium and •-•.•-:j-herc--! bedrock of lower Turpentine Run. The •'.epth =f the rock wells is not necessarily a cri- :°r:or. of ;reater yield, but is usually an indica- •; jn or where a zone of water-bearing fractures ••••as oenetrated. Short-term yields from indi- vidual rock wells in the upper basin are as great •>s 1 5 u , J O O g p d . Sustained yields , however, r;nqe from about 3,000 to 30,000 gpd. Indi- •.••- .u.jl wells in lower Turpentine Run yield as r en is JO,000 gpd, but sustained ground-water .vr.l-.dnv.v.us of more than 10,000 gpd will probably result in sea-water encroachment. .1 round-water levels.—Contours of the ground- •.vacar surface during August 1965 and January 1066, ore shown in figures 31 and 32. The arrows on these maps indicate the general direction of ground-water movement. In the upper basin, v/hen water levels are high, ground-water flow is split—part moving along the course of Turpentine Run .ind part moving through the fractured and altered zone at Mt. Zion and emerging as a series of springs discharging to Turpentine Run in the lower basin. When ground-water levels are low in tne uoper basin, nearly all ground water is .rooabiy discharged through the fractured zone at Mt. Zion, and a temporary ground-water divide is established at the position shown in figure 31. Ground-water levels in the basin fluctuate in relation to discharge from and recharge to the aquifers. Figures 29 and 27 are the hydrographs of wells 19 and 24 drilled in bedrock in the upper basin and in the alluvium and weathered rock of 41 TOT REFERENCE NO. 17 No data base is available for a detailed assessment of population within a particular radius of the site. The best available information follows this note, and consists of a 1980 census by water district. Populations were estimated by adding together the populations of each district within the radius of interest. In cases where only a portion of a district is within the radius, population was prorated by area. Km BUTOS i i r r r r iiii i ii FINAL REPORT-FINAL WATER MANAGEMENT PLAN FOR THE ~ PUBLIC WATER SYSTEM Prepared for THE DEPARTMENT OF " --—-—---------- CONSERVATION AND CULTURAL AFFAIRS GOVERNMENT OF THE VIRGIN ISLANDS \ CH2M SSHILL Prepared by CH2M HILL SOUTHEAST, INC Project No. GN14325JVO July.1983- e;oo • I •» sf £ F 3 H f lis i h §&£§ t^iisSiEiiiiSiiHs "i«2?i » ***r J4 ^.^ ,r ««M ^^ •* ^^ft^^b M ^ • ^ ^M ^V* * i* ^ ^ *• V1 *• * * w i vSSWZiS^MMMMM S^ i 5 S « M 3 w v r ^**** v^ *• ' « * *•* tf 4 *S i 5|Ei!|EC5555wKStv S a9w> > ^9>*MiE»M*»»^**wi»*' • 1* •»*F'-o I i! : : ici: i til*: :5I5: ;*!s:s::s; :ss« KiEiStSv iS:iE&8: : i : Mitts: if i5 is: :sas: :s :ssss 3: : ss :: s* :its: »**«:: [f ^1 1 is P* ** i F ' B- •««» -5«i- M w 15 i > » * M I * W * » -• < • =-? as, as 8, rs .? , . st. I»I > » w > S «3~ > *•* x i **f ivi I O W M <-« HP .of n«. 1C I K t U* I t • W*rf t I £ ^t* to*M I M M I I M l S 5 * > i v > e I H* M I M r* ." IT* ^O *• «- ^ f*- V* [o ^ •• M »M •»%*V^*V ~ M * K s ls55»£s==fs«ssssBK5: "o *• ^J*> ^V ^ v*> u> * •> V is Ssssssss? -sssssss.- I? J» ••r; lls s b::5Ss:i5Is:s:?:;s5i a=i?52:-I : = : :5Ss *• ' M i » ( I v * 011 w i i - a Ifl j s : : sings* flSr .r > • ! o mi •^io -< x JT m OJ C i 0*1 A fittt TEAP TV8o ———— INTERNAL DEMAND ,» •-——————.....— I Ml CANAL MATER SUPPLY -————— — ————— • •——— POTABLE MATER ———• •-- NON-POTABLE MATCH--* POTABLE NON-POt TOTAL CISTERN OTHER IOIAL SALT OTHER IOIAL KCAL/O KCAL/O KCAL/O KCAL/D KCAL/O KCAL/O KCAL/O KCAL/D KCAL/O EXTERNAL OCMANO ———« POTABLE KCAL/O NON-POT KCAL/O TOTAL KCAL/O DISTRICT OltTHICT OISIHICT DISTRICT OISIAICI DISTRICT OISIRICI UISTRICT OIStRICI UISTRICT DISTRICT . DISTRICT DISTRICT DISTRICT DISTRICT OISIRICT DISTRICT DISIRICt DISTRICT DISTRICT Ol 01 01 04 Oft 06 07 OB 09 10 1 1 12 13 14 19 16 17 IB 19 2O 47.9 271.7 670. B 13*. 9 2*.l 37.lt 293.B>> " 286. « 248*. B 11 131. 1 233.0 607.1 134.7 29.2 1 IB. 9 96.7 43.3 2.6 18.9 318.9 0.0 47.9 36.1 307.7 0*0 670. B B.O 139.9 a 4* 29.1 . f^B 37.7 ''**• 293. B *'"••« 2B6.2 MBB.O 21486.0 8. 131. 1 0. 233.0 27. 634.9 B. 134.7 O. 29.2 90. 168.9 O. 96.7 7. 91.0 0.0 2.6 0*0 ' 18.9 37.2 399.6 1 4! IK 1 t 1 6< 3S IIC 24 31 91 Jl 9C r.4 o.i 1.7 O.I >.a 9. >.4 100. k.9 a. k.3 0. t.2 0. >.a si. 1.9 4123. >.l 0.( r.9 O.C k.2 O.C .9 O.C .0 O.C .9 90. C .1 9.C .4 IIO.C .4 O.C .4 «.C 1.8 O.C > . 7.4 ) 49.7 119. B 109.4 6.9 6.3 64.2 90. B 4234.4 ) 29.1 > J7.9 > ' 96.2 > JI.9 > 6.O ) 99.9 > 1 1 .1 > 119.4 » 0.4 » 3.4 I 9O.B 0.0 0.0 0.0 0.0 0.0 0.0 O.O 0.0 2IOOO.O 0.0 O.O 0.0 .0.0 0.0 0.0 0.0 o.o 0.0 0.0 0.0 0.0 0.0 0.0 0.0 o.o 0.0 0.0 0.0 0.0 0.0 o.o 0.0 0.0 o.o 90.0 90.0 10.0 0.0 0.0 0.0 0.0 o.o 0.0 0.0 0.0 o.o 0.0 o.o 21000.0 0.0 0.0 0.0 o.o 0.0 90.0 90.0 10.0 o.o 0.0 0.0 4O.5 226.0 999.0 26. 1 22.2 31.4 229.6 236.9 419.3 102. O 199.1 99O.9 IO3.2 19.2 98.6 90.5 24.2 2.2 15.9 267.7 0.0 36.2 O.O 0.0 o.o 0.0 o.o 0.0 o.o 0.0 0.0 27.6 O.C O.O O.O o.o o.o o.o 0.0 37.2 40.9 262.2 999.0 26.1 22.2 31.4 229.6 236.9 419.3 102.0 199.1 978.5 103.2 ' 19.2 98.6 90.5 24.2 2.2 19.9 3O4.9 IQfAL ISLAND 99B8.J 19196.7 29146.9 6J8.I 4444.9 90*2.6 2IOOO.O 110.0 21110.0 J2II . 7 101 .C J3I2.7 Snvic* Ditliicu «• Numlwtd FIGURE 3-4. Projected demand of the service districts on St. Croix for the year 1980. ISLAND Of S' THOMAS UUlPUl UAIf »« YEAR I960 ».— . INTERNAL DEMAND ——• • ———— ——-——— INTERNAL HATER SUPPLY - ——— - —— — -• «, — — POTABLE MATER —4-» «— NON-POTABLE «ATER--« POTABLE NON-POI TOTAL CISTERN OIH£R TOTAL SALT OTHER TOTAL KCAL/0 KCAL/O KCAL/O KCAL/O KCAL/D «CAL/D KCAL/D KCAL/O KGAL/D EKltHNAL OtMANO ---« POIABLE KGAL/O NON-PUT KCAL/O 101 AL KCAL/O DISTRICT OISIRICI DISTRICT DISTRICT DISTRICT DISTRICT DISTRICT DISTRICT DISIRICI DISTRICT OISIHICI DISTRICT DISTRICT DISTRICT DISTRICT DISTRICT DISTRICT OISIRICI DISTRICT 01 02 03 04 09 06 07 OB 09 10 I I 12 13 I* 15 16 17 IB 6 IV 21. 89 137. 984. 104. •X. 940. «r. so. : 174. ! 2*1. 40. 216. 712. 567. 2 0.6 29.7 0.0 0.0 0 oI «* If* . • 0II 0 10 oi . I c.o 26.J 97.6 2O. 7 0.0 0.0 6. It 27 89 138. 616. 2IO. 82. 940. 108. 90. 189. 342. 00. «• •• I . 76V. 987. 0.6 2S.7 I .4 4.1 9.0 22.1 34.7 83.8 20.3 I 1.2 102.8 13.1 J.4 28.6 40.O 9.7 J3.8 I 12.7 V3.9 O.I J.6 0.0 O.O O.O O.O 0.0 30.O 69.0 a.o 16.0 0.0 0.0 10.0 170.0 0.0 0.0 8.0 29.0 0.0 0.0 4.1 9..J 22. I 34.7 I 13.8 89.4 19 118 13.I, J.4 38.6' 210.0 9.7 J3.8 120.7 118.9 O.I 3.6 O.O O.O O.O 0.0 O.O 0.0 0.0 0.0 O.O O.O 0.0 O.O .0.0 O.O O.O O.O 0.0 0.0 O.O 0.0 0.0 0.0 O.O 4.O 0.0 96.0 0.0 0.0 19.0 0.0 19.O 62.0 0.0 .1.0 ti.O O.O 0.0 O.O 0.0 0.0 0.0 0.0 4.0 0.0 56.0 0.0 0.0 19.O 0.0 is. o i.t.O 0.0 0.0 d.o 0.0 0-0 J. J 9.4 19.6 22.9 63. 7 102.3 479. f 7J.4 63.3 422.2 83.9 46.9 139. 7 I 95- « 31 .0 |8| .*> 991 .3 44B. 7 O.b 22. I 0.0 o.o 0.0 O.O O.O 31.8 90.0 O.O O.O O.O 0.0 O.O 4.* O.O 26. J 97.6 2O. 7 0.0 O.O 9.4 19.6 22.9 63. 7 102.3 907.9 I2J.4 63.3 422.2 B3.9 46.9 I 39.7 20O.O 31 .0 2O7.9 64B.9 4b9.4 0.9 22. I TOTAL ISLAND 3794. B 3^7. (> 4O8I.8 623.9 332. O 999.9 O.O 192.0 152.0 29d6.O DitliKli wt NiMnljeiiH \ IV0.6 Jl76.6 FIGURE 3-6. Projected demand of the service districts on St. Thomas for the year 1960. REFERENCE NO. 18 NUS CORPORATION TELECON NOTE REFERENCE NO. 19 NUS CORPORATION TELECONNOTE CONTROL NO: DATE: TIME: DISTRIBUTION: •ETWEEN: OF: (j PHONE: AND: INUSI OtSCUSSION: tQg.qL o<^ J> • i uJCLS,V\ Fefvw-I-sf" -+• Lk-rC.ll tH.T^rYV\£i~T~ie-^_ Q-r< TT cV->/v\ _ li'c LOork_S" rip r> I cifuj \) itt A- u - >r r\ ow^ «<O *^-C—V «v>Q^ . jJii nT- sV\Crf^ ~A&/» • . Y\fl, C-k.j'4 w .^TWs Q.V ~ \»i To ( Qt ^\'4-i >v-/ Vxju^rv MUStMTMMHOOMI Mi——f NUS CORPORATION TELECOM NOTE CONTROL NO: OATt: TIMI: DISTRIBUTION OZ r ( PMONf: AND: L) (NUSI DISCUSSION: — \Ci d' (vv-<- tvCTB J 1 ~TTi \^ i>t"rO 2- V^e rovOv / < ct \fc> *4- PL ACnONITUM: i-s^ r^-^v^cN "r-ie-.— dv^ O"t - ru ?^^t75tf ) • REFERENCE NO. 20