UMASS/AMHERST 312Dbb DE7D flMSb 5 MASSACHUSETTS GROUND-WATER QUALITY y tffl'Ve/5% 0/ #M Nantucket Island ?*-«t Figure 1. Selected geographic features and 1985 population distribution in Massachusetts. A . Counties, selected cities, and mapr drainages. B. Population distnbu- tion, 1985; each dot on the map represents 1,000 people. (Source: B. Data from U.S. Bureau of the Census 1980 decennial census files, adjusted to the 1985 U.S. Bureau of the Census data for county populations ) WATER QUALITY IN PRINCIPAL AQUIFERS Massachusetts has four principal types of aquifers (fig. 2/4)— stratified drift; sedimentary-bedrock; crystalline, metamorphic and igneous bedrock; and carbonate rock (U.S. Geological Survey, 1985, p. 249-252). Virtually all the State's ground-water withdrawals for public water supply are from the stratified-drift aquifers. In southeastern Massachusetts, on Cape Cod, and on the islands of Martha's Vineyard and Nantucket the stratified-drift aquifers are the only water source for both public and domestic supply. However, in other parts of the State, about 300,000 people rely on domestic wells in the bedrock aquifer. Background Water Quality A graphic summary of selected water-quality variables com- piled from the U.S. Geological Survey's National Water Data Storage and Retrieval System (watstore) and the mdeqe is presented in figure 2C. The summary is based on dissolved-solids, hardness, pH, sodium, and sulfate analyses of water samples col- lected from 1979 to 1985 from the principal aquifers in Massachusetts. Percentiles of these variables are compared to na- tional standards that specify the maximum concentration or level of a contaminant in drinking-water supply as established by the U.S. Environmental Protection Agency ( 1986a, b). The primary max- imum contaminant level standards are health related and are legally enforceable. The secondary maximum contaminant level standards apply to esthetic qualities and are recommended guidelines. The secondary drinking-water standards include maximum concentra- tions of 500 mg/L (milligrams per liter) dissolved solids, 6.5-8.5 units of pH, and 250 mg/L sulfate. Stratified-Drift Aquifers The stratified drift consists of layers of unconsolidated sand and gravel, whose mineral composition is commonly more than 99 percent quartz and feldspar, which are chemically stable, nonreac- tive. and virtually insoluble in water. Because of the chemical com- position of both the aquifer and precipitation, water from the st ratified -drift aquifers generally has small concentrations of dissolved solids and is soft and slightly acidic (fig. 2C). In the western part o( Massachusetts, the stratified drift locally derived from carbonate rocks has a mineral composition similar to local bedrock and. therefore, possesses water chemistry similar to that described here for the carbonate rock aquifer The median dissolved- solids concentration was 88 mg/L based on 697 samples of water from public-supply wells in the stratified-dhft aquifers analyzed by the mdeqe in 1984. and the median hardness as calcium car- bonate was 32 mg/L. Most public and private wells in this aquifer are less than 100 feet deep, and the aquifer generally is unconfined. The water is commonly nearly saturated with dissolved oxygen and has a relatively constant temperature of about 1 1 °C (degrees Celsius). Eighty-five percent of the 697 analyses had a pH of less than 7; the median pH was 6.3. Because the water has a small dissolved-solids concentration and is soft and acidic, it is corrosive to metal and cement pipe. Of 697 analyses of water from public- supply wells. 75 percent had negative Langelier indexes of —2.5 or lower; and the median index was — 3.23. Water with a negative Langelier Index (Hem. 1970. p. 24) is undersatu rated with respect to calcium carbonate and. therefore, may dissolve metals and ce- ment releasing lead, copper, zinc, and perhaps other metals. Sodium hydroxide or other chemicals are added to some public-water sup- plies to increase the pH and decrease corrosivity. In 1986. plumb- ing codes were changed to limit the lead content of solder to less than 0.02 percent, thereby decreasing the potential for dissolution of lead from plumbing. Consumers are advised to flush water which has been in domestic copper plumbing or lead service lines before drawing water for drinking or cooking. The metals may impart an acerbic taste to the water and copper causes blue-green staining of white porcelain sinks and tubs. Iron and manganese may occur in concentrations requiring treatment before distribution in public supplies These elements are the products of the weathering of minerals and dissolution of oxide coatings on aquifer materials. They are easily dissolved in acidic water in the absence of oxygen. Water in the stratified drift is almost always acidic, but commonly contains dissolved oxygen, which precludes the solution of iron and manganese However, dissolved oxygen may be depleted when ground water passes through organic deposits, such as peat or river-bottom sediments, thereby allowing the water to dissolve and mobilize iron and manganese. For example, in Middlesex County, a test well located in an aquifer below a 5-foot thick layer of peat yielded water with 19.000 /ig/L (micrograms per liter) dissolved iron. In addition to causing taste. color, and staining problems, iron and manganese can form en- crustations on well screens, thereby decreasing well efficiency. Wells, which initially yield water with small concentrations of these metals, may show a trend toward increasing concentrations and decreased well efficiency as a result of reversing ground-water gra- dients and causing iron- and manganese-bearing water to flow to the well (Gay and Fnmpter. 1981. p 18-23) Aquifers that pre- viously had been bypassed because of large concentrations of iron and manganese are now being developed and the water treated because of increased demand and limited resources. Organic deposits can cause other problems in addition to large concentrations of iron and manganese In Provincetown. on the northern tip of Cape Cod. decomposition of organic material in marsh deposits that have been buried by postglacial sand dunes, produces dissolved ammonia, hydrogen sulfide, and iron in the ground water (Fnmpter and Gay. 1979. p. 7-9). Saltwater intrusion into the si ratified -drift aquifers has been caused by overpumping in some coastal areas of Massachusetts, but no public-supply well fields have been closed and only one has been affected. Public-supply wells for Provincetown Barnstable County draw freshwater from the upper 100 feet of the stratified- dnft aquifer, but overpumping has caused gradual upward migra- tion of saltwater that underlies the shallow freshwater lens in this area. Sodium concentrations have increased from less than 25 to 150 mg/L at one well field. The intrusion has been controlled by decreasing pumping rates in the well field and by areally distributing withdrawal from the aquifer. Massachusetts, which has a 20-mg/L guideline for sodium in public drinking water, requires that sup- pliers notify all their customers if that guideline is violated. Sedimentary-Bedrock Aquifer The Triassic sedimentary-bedrock aquifer in the Connecticut River valley has been developed for private domestic supplies and a few industrial supplies. It consists of sandstone, shale, con- glomerate, and interbedded lava flows (traprock). Deposited in a continental basin environment, these rocks contain traces of gyp- sum, a mineral characteristic of evaporite deposits. Localized ore deposits and prospects contain copper, lead and zinc sulfides. fluoride, and secondary uranium-bearing minerals. The ground water is slightly alkaline and has a median pH of 7.9. Water from the upper 200 feet of this aquifer generally contains moderate levels of dissolved solids and is moderately hard, but water from deeper parts of the aquifer commonly has large concentrations of dissolved solids and is hard. The median dissolved-solids concentration of 15 samples was 360 mg/L, but one 510-foot deep well yielded water with 1.600 mg/L dissolved solids. The water in this aquifer con- tains larger median concentrations of sulfate (120 mg/L). sodium (21 mg/L), and fluoride (0.2 mg/L) than any other aquifer in Massachusetts. Carbonate-Rock Aquifer The carbonate-rock aquifer consists of limestone, dolomite, and marble interbedded with schist and quartzite in the valleys of Berkshire County in western Massachusetts. This aquifer has been developed for domestic supplies and for large-yield wells by in- dustry. Water from this aquifer characteristically is very hard (me- dian 210 mg/L as calcium carbonate) and has moderately large dissolved-solids concentrations (median 220 mg/L). but unlike the sedimentary-bedrock aquifer has little sodium (median 3.7 mgL). sulfate (median 17 mg/L). and less than 0.1 mg/L fluoride. The water is also slightly alkaline and has a median pH of 7.8 Crystalline-Bedrock Aquifer The crystalline-bedrock aquifer is composed predominantlv of granite, gneiss, and schist, and is relied upon for domestic water supplies, for which only a few gallons per minute are needed and where there are no other easily accessible aquifers. Virtually all water in this aquifer has small dissolved-solids concentrations, with a median concentration of 120 mg/L. It is moderately hard, with a median concentration of 90 mg/L (as calcium carbonate) and is slightly alkaline, with a median pH of 7.8. Iron in concentrations requiring treatment before use is common in those rocks known as *" rusty" schist or gneiss which contain an abundance of fer- romagnesian minerals or small amounts of pyrite or pyrrhotite. Arsenic, possibly derived from sulfide minerals, has also been found in concentrations between 1 and 560 iig/L in a few wells in Hamp- den. Worcester, and Middlesex Counties. The median arsenic con- centration in 33 samples was 1 1 .5 tig/L. The primary drinking-water standard for arsenic is 50 /xg/L. Local variations of bedrock mineralogy affect ground-water quality, particularly where car- bonate lenses and sulfide-bearing zones occur in the bedrock of Mid- dlesex County Radon concentrations larger than 10.000 picocunes per liter have been detected in water from crystalline-bedrock aquifers elsewhere in New England. New York, and Pennsylvania. and in the Triassic sediments of Connecticut and New Jersey. The gas is likely to be present in similar concentrations in some loca- tions in Massachusetts. Effects of Land Use on Water Quality Most of Massachusetts" population and water-quality prob- lems are located in the eastern third of the State (figs. 1 and 3). Water quality has been degraded mainly because of the effects of waste disposal, urbanization, and agriculture. Slightly more than 100 of about 1.400 public-supply wells or well fields have been closed since 1960 because of contamination (fig. 3fl). The total pumping capacity of these closed wells was 54 Mgal/d (million gallons per day), about 7 percent of the State's 765 million gallon average daily demand. Nearly all of the contaminated public-supply wells were identified through programs of periodic water-quality analyses and special organics testing to protect public health by the mdeqe. About 1.400 public-supply wells constitute an extensive ground-water-quality monitoring network in Massachusetts. Sampling consists of frequent bacterial tests, annual analyses for common inorganic constituents and properties, and for metals and organic compounds testing on a 3-year cycle at a minimum. Waste Disposal Hazardous waste, which is treated, stored, or disposed of at 31 sites identified under rcra constitutes a known or possible potential hazard to the quality of ground water (fig. 3/1). The Massachusetts Division of Solid and Hazardous Waste has deter- mined that some contamination of ground water has been detected at 19 of these sites. Sixteen sites have been included and 5 addi- tional sites have been proposed for inclusion on the U.S. En- vironmental Protection Agency's npl under the Comprehensive En- vironmental Response, Compensation, and Liability Act (cercla) of 1980. Contaminants have been detected in ground water at 16 of the cercla sites. Many of the hazardous materials sites are located in populous eastern Massachusetts (fig. 3/4 ). As of September 1985. 37 hazardous-waste sites at 6 facilities in Massachusetts had been identified by the U.S. Department of Defense as pan of their Installation Restoration Program (irp) as having potential for contamination (U.S. Department of Defense. 1986). The irp. established in 1976. parallels the epa Superfund program under cercla. The epa presently ranks these sites under a hazard ranking system and may include them in the npl. Five sites at one facility (fig. 3/4) were considered to present a hazard significant enough to warrant response anion in accordance with cercla. The remaining sites were scheduled for confirmation studies to determine if remedial action is required. Organic compounds from industrial waste, mostly solvents, are the major ground-water contaminants in the State— 56 public- supply wells have been closed because of contamination with organics. A few wells have been reopened, but require treatment of the water by both air stripping and activated-carbon filtration. Waste lagoons, pits, landfills, transfer stations, improper storage, and illegal discharge are the major avenues at contamination for extremely mobile and persistent organic compounds. Organic wastes are commonly associated with chemical and electronic industries. machine and electroplating works, aircraft engine cleaning, tank- truck and drum washing, and leaking sewer lines. Many of the public-supply wells contaminated with organic compounds are in or near industrial parks. The most common contaminants are trichloroethylene. methyl chloride, and tetrachloroethylene. but ad- ditional compounds that have also been identified include 1 , 1 dichloroethylene. 1 .2 dichloroethylene. 1.1 dichlorethane. 1.1.1 trichloroethylene. methyl ethyl ketone, methyl isobutyl ketone, tnchlorofluoromethane. dioxane. carbon tetrachloride, chloroform, acetone, benzene, toluene, and phenols. Disposal of domestic sewage in the ground has been ta.ored by sanitary engineers and regulatory agencies Land disposal through septic systems and municipal facilities is still the method of choice on the State's two sole-source aquifers. Cape Cod and Nantucket. partly as a consequence of the State's Ocean Sanctuaries Act which prohibits new discharges of wastewater to the ocean. Municipal wastewater recharges the ground through seepage lagoons at several sewage-treatment facilities. About one-third of the State's housing is serviced by septic systems that discharge underground. Numerous private wells and some public-supply wells have been contaminated by wastewater containing nitrates or organics or both. One public- supply well, located 7,500 feet downgradient from sewage-treatment plant lagoons, has been contaminated with organics and showed increased concentrations of nitrate, detergents, boron, and dissolved solids (LeBlanc, 1984. p. 11-22; Thurman and others. 1984 p. 58-63). The Massachusetts Division of Water Supply estimates that there are 241 active and 243 closed municipal landfills in Massachusetts (fig. 3C). At least six public-supply well fields and an uncounted number of private wells have been closed as a result of contamination attributed to landfills. Leachates from landfills commonly cause ground water to contain large concentrations of iron, dissolved solids, and nitrogen (as ammonia or nitrate), but most well closures have resulted from contamination by organics. Inappropriate disposal of waste organics and septic-system de- greasing solvents in landfills are the sources of these persistent con- taminants. Since 1971, capping of landfills with a relatively im- permeable material has been part of the closure requirements The mdeqe now requires ground-water protection systems, such as liners, leachate-collection systems, and ground- water quality monitoring, for all new landfills and all expansions of landfills. Urbanization Twenty of about 1.400 public-supply wells in Massachusetts have been closed in response to unsatisfactory water-quality con- ditions that can be attributed to the effects of urbanization. The causes of closures may be divided into three major groups— road salt, oils and fuels, and sewage. Road salt stored and applied to roads for ice and snou con- trol has contaminated nine public wells and an uncounted number of private wells. Three public-supply wells in Weston (Middlesex County) have been closed because of contamination by road salt. Two of these wells were located in the stratified-dnft aquifer near a major superhighway intersection including two large toll plazas where "bare pavement" is a highway mainten.: ve policy In Yap- mouth on Cape Cod. a public-supply well in the stratified-dnft aquifer was closed because of large concentrations of salt that had been leached by rain from an uncovered salt-storage pile. A scavenger well pumped to remove salt from the site was estimated to have removed 835 tons of salt during 29 months (Fnmpter and Gay. 1979. p. 7) . In 1967 the Massachusetts Department of Public Works (mdpw) began covering ail of it's stored salt to prevent leaching. Also, in 1978 the Department began providing financial assistance to towns and municipalities for the purpose of covering salt stockpiles. By February of 1987. the mdpw built, or provided financial assistance for building. 395 salt-storage sheds. The salt to sand mixture ratios have been decreased on selected highv,a\s. experiments with calcium magnesium acetate as an alternative deicing chemical have begun, and evaluation of pavements which contain encapsulated calcium chloride or rubber particles is planned. Private wells along highways also are susceptible to road- salt contamination, particularly where more than average amounts of salt are applied at dangerous intersections. For example, near an intersection on a hill in rural Pelham (Hampshire Counn i. a private domestic-suppK well was drilled to a depth ot 121 teet deep into the crystalline-bedrock aquifer to replace a 25-tooi deep well in till that had become contaminated with salt. Soon, that well became contaminated and a new 740-foot deep well was drilled, but that too became contaminated with salt and the property was abandoned as a homesite and the house was removed. Drilling deeper to avoid road-salt contamination has not been a dependable solution in Massachusetts. Private and public wells have been contaminated by fuel oil or gasoline in several widely scattered locations. A public-supply well field in the stratified-drift aquifer in Truro, which serves Provmcetown on Cape Cod. was closed because of a gasoline leak from a nearby underground storage tank This closing required the development of a temporary emergency-supply well and created increased demands on other well fields where withdrawals must be limited to prevent saltwater intrusion. Domestic wells have also been affected by fuel leaks and spills. For example. 68 domestic wells, more than 95 percent of which are in the crystalline-rock aquifer in Walpole and Dover (both in Norfolk County), were af- fected oy a gasoline leak from an underground storage tank. The leak was stopped and the immediate water-quality problem was solved when the oil company, on it's own initiative, provided public water to the homes. The mdeqe has established a 400-foot radius for sanitary pro- tection about a public-supply well which successfully protects against biological contamination. Degradation of private and public sup- plies by sewage from leaking sewers, cesspools, and septic systems occurs mainly in the form of large nitrate levels and organic com- pounds. Of 5. 1 18 chemical analyses of private-supply wells in Barn- stable County from 1979 to 1986. 130 wells had nitrate (as nitrogen) concentrations that equaled or exceeded the primary drinking stan- dard ol 10 mg'L (U.S. Environmental Protection Agency, 1986a). ana 194 had from 5 to 10 mg/L nitrate (as nitrogen). Most of these occurrences are most easily explained as caused by septic systems and lawn fertilizers Increasing levels of nitrate have been observed in some public-supply wells and attributed to urban congestion and domestic wastewater (Frimpter and Gay, 1979. p. 9-10). but this condition has not been identified as a cause of recent public-supply well closures. Agricultural Practices Agricultural pesticides have been detected in ground-water supplies in the farming areas of the Connecticut River valley in central Massachusetts. Public-supply wells in Southwick (Hamp- ton County) and Deerfield (Franklin County) have been closed because of contamination by ethylene dibromide. which was used as a soil fumigant in the growing of tobacco. The four closed wells in Southwick represent two-thirds of the West Springfield water supply, which serves 27.000 people The closed well in Deerfield was a standby well and not used, but water from 52 private wells in the Connecticut River valley has been identified as exceeding the standards for a number of pesticides including ethylene dibromide. 1-2 dichloropropane. aldicarb. alachlor. carbofuran. and dinoseb Also, in southern Bristol County, where potatoes are grown, eight private wells contained aldicarb and one other well contained alachlor at levels exceeding the standards. Of the 556 suspect wells tested by the medqe. 28 percent contained detectable amounts of pesticides and 1 I percent exceeded the drinking-water standards Although an actual count is not available, most of the affected wells draw water from shallow water-table aquifers in un- consolidated glacial drift. Potential for Water-Quality Changes For public water supplies, there are generally no deeper aquifers that can be used as alternatives to the unconfined and shallow unconsolidated stratified -drift aquifers A l-Mgal/d public- supply 'acII may draw water from a recharge /one as large as I square mile around the wellhead. These zones, where water table is commonly less than 25 feet below land surface, are extremely susceptible to contamination (figs. 2A.B). Because the small aquifers are recharged within a short time (Knott and Olimpio. 1986, p. 15-24). they are able to sustain the large withdrawals necessary for public supplies. These conditions also allow relatively rapid flow of contaminants, making restora- tion a more rapid process (tens of years) than is typical (centuries) in many of the aquifers in the rest of the Nation (James, 1986. p. 4-6). Because of continued urbanization and land disposal of wastes (fig. 3C), water demand will continue to increase and ground-water quality may be expected to be further degraded. As a result, there may be continued demand for longer and larger water diversions to the urbanizing areas, and ground-water-treatment plants may become common, rather than exceptional. State and local govern- ments, as part of the management of ground-water quality, are now designating zones of degraded water to increase identification and protection of supply. GROUND-WATER-QUALITY MANAGEMENT In 1983. the mdeqe adopted a ground-water protection strategy, "to protect the quality and quantity of groundwaters to the levels necessary for projected future use.** The mdeqe has developed, and is continuing to develop, a program to prevent ground water from being degraded to a quality less than its intended use. and to manage known or suspected contamination. The respon- sibility for assunng the protection of ground-water quality is shared between local government and the State. Towns and cities have primary responsibility for ground-water quality because they are the only government entities with authority to control land use. The State has regulatory control of all public water supplies, sanitary landfills, hazardous waste, underground storage tanks, industrial wastewater discharges of any size, and sanitary wastewater discharge facilities of 15.000 gallons per day or more. Local govern- ment has control of land use. of sanitary wastewater disposal of as much as 15,000 gallons per day. and of private wells. The State Fire Marshall regulates underground storage tanks and the regula- tions are enforced by local Fire Chiefs. State regulatory guidance is provided through public water- supply regulations, sanitary-landfill regulations, hazardous-waste- management regulations, land application of sludge and septage regulations, wetlands regulations, onsite and municipal wastewater treatment regulations, and ground-water discharge permitting and classification (S. Roy and D. Terry, Massachusetts Division of Water Supply, written commun.. 1986). All discharges to the ground water of the State must meet Massachusetts drinking-water standards and health advisories established by the epa. except discharges to ground water specifically identified and permitted to be degraded. A second major element of the program is technical assistance and information. Publication of handbooks and a newsletter and presentation of numerous educational and information workshops are part of this element. Technical assistance is provided for the implementation of local ground-water protection through a series of 1 :25.000-scale map overlays containing geographic information for aquifers, public-water supplies, waste -disposal sites, and surface- water drainage divides. A long-range program of water-resources appraisal and aquifer mapping by the U.S. Geological Survey in cooperation with the Massachusetts Division of Water Resources is now nearly statewide in scope, and results are contained in a series of 24 US. Geological Survey Hydrologic Investigations Atlases. In addition to regulatory guidance and technical assistance. Massachusetts is encouraging local management and protection of water supplies by providing economic assistance. Under Chapter 286 of the Acts of 1982. funds are provided to communities for immediate response to the emergency and remedial cleanup of con- taminated punlic water supplies. This Act also provides funds to communities for the delineation of zones of contribution (that part of an aquifer which contributes water to a public supply well) and the purchase of land, development rights, or easements necessary to implement long-range protection of ground-water supplies. This economic incentive is a step that encourages towns and cities to develop measures to help ensure adequate supplies of good-quality ground water for their future and for the future of the State. SELECTED REFERENCES Cape Cod Planning and Economic Development Commission. 1983. Regional groundwater management needs. Cape Cod. Massachusetts: Barnstable. Mass.. 69 p. Fnmpter. M.H. 1981. Ground water for management: Cornell University Conference. Groundwater Use Management in the Northeastern States. June 2-4. 1981. Ithaca. NY., p. 95-103. Fr ■npter. M.H. and Gay, F.B., 1979. Chemical quality of ground water >n Cape Cod. Massachusetts: U.S. Geological Survey Water-Resources Investigation Report 79-65, II p. Gay. F.B and Frimpter. M.H., 1981. Distribution of polychlonnated biphenyls in the Housatonic River and adjacent aquifer. Massachusetts: U.S. Geological Survey Water-Supply Paper 2266. 26 p. Hem. J. D . 1970, Study and interpretation of the chemical characteristics of natural water: 2nd. Edition. U.S. Geological Water-Supplv Paper 1473. 363 p. James. I.C.. II, 1986. Groundwater in the Northeast: 1985 Annual Con- ference. Coalition of Northeastern Governor's Conference Summary. p. 4-6. Knott. J.F. and Olimpio. J.C.. 1986. Estimation of recharge rates to the sand and gravel aquifer using environmental tritium. Nantucket Island. Massachusetts: U.S. Geological Survey Water-Supply Paper 2297. 26 p LeBlanc. D R . 1984. Sewage plume in a sand and gravel aquifer. Cape Cod, Massachusetts: U.S. Geological Survev Water-Supplv Paper 2218. 28 p. LeBlanc. DR.. Garabedian, S.P.. and Gelhar. L. W., 1986. Preliminary results of a natural-gradient tracer test in a sand and gravel aquifer. Cape Cod. Massachusetts (abs.): eos. v. 67. no. 16. p. 286. Thurman. E.M.. and others, 1984. Sewage contaminants in ground water. in LeBlanc. DR.. ed. Movement and fate of solutes in a plume of sewage-contaminated ground water. Cape Cod. Massachusetts; U.S. Geological Survey Toxic Waste Ground-Water Contamination Pro- gram: U.S. Geological Survey Open-File Report 84-475. 180 p. U.S. Department of Defense. 1986. Status of the Department of Defense Installation Restoration Program — Information paper: Washington. DC, U.S. Department of Defense. Office of the Assistant Secretary of Defense (Acquisition and Logistics). Environmental Policy Direc- torate. February, 35 p. U.S. Environmental Protection Agency, 1986a. Maximum contaminant levels (subpart B of part 141. national interim primary drinking- water regulations): U.S. Code of Federal Regulations, Title 40. Pans 100 to 149. revised as of July 1. 1986. p. 524-528. 1986b, Secondary maximum contaminant levels (section 143 .3 of part 143, national secondary drinking-water regulations): U.S. Code of Federal Regulations. Title 40. Parts 100 to 149. revised as of July 1. 1986, p. 587-590. 1986c, Amendment to National Oil and Hazardous Substances Con- tingency Plan: national priorities list, final rule and proposed rule: Federal Register, v. 51. no. 111. June 10. 1986. p. 21053-21112. U.S. Geological Survey. 1985. National Water Summary 1984. Hydrologic events selected water-quality trends and ground-water resources: U.S. Geological Survey Water-Supply Paper 2275. p. 249-254. Prepared by Michael H. Frimpter, U.S. Geological Survey. FOR ADDITIONAL INFORMATION: District Chief. Massachusetts Office. U.S. Geological Survey. 150 Causeway Street. Suite 1309. Boston. MA 021 14 47 ST i Numeral » aquifer PRINCIPAL AQUIFER number in figure 2C Ml Stratified drift aquifers 11) | Till - Forms a fairly continuous cover over bedrock jnns Inoi shown on map) Sedimentary bedrock (2) j Crystalline bedrock 131 | Carbonate bedrock 14) Not a principal aquifer WATER-QUALITY DATA Percentile Percentage of analyses equal to or less than indicated values 90th 75th -50th 25th - 10th National drinking water standards Maximum pt-r missibie SQMiamiridW level unmaryi - — — Maximum recommenced .onramman! evei 'Secondary' Maximum recommended range ijH secondary) Maximum recommended intarnmai I »vei neaith advisory' Reporting limit Minimum reporting :evet wirh analytical merhocJ used NUMBER OF ANALYSES 300.000 ■"JL^'' Jl — — -DISSOLVED »-.j, LANDFILL SITE County and municipal landfills, by county - Active and inactive 1-3 4-10 Mi 11-20 ■■ 21 50 I More than 50 Figure 3. Selected waste sites and ground- water-quality information in Massachusetts. A, Comprehensive Environmental Response. Compensation, and Liability Act iCERCLA) sites, as ot 1986, Resource Conservation and Recovery Act. (RCRAl sites, as of 1986, Department of Defense Installation Restoration Program iirp) sites, as of 1985 B, Distribution of wells that veld contaminated water, as of 1960-86 C, County and municipal landfills, as of 1986. ISources: A, Massachusetts Department of Environmental Quality Engineering files. U S Environmental Protection Agency, 1986c, U S Department of Defense. 1986 8, Massachusetts Department of Environmental Quality Engineering files C, Massachusetts Division of Water Supply files. • I ) <