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The Extent of Groundwater Contamination in the United States 1 VERONICA I. PYE and JOCELYN KELLEY The Academy of Natural Sciences of Philadelphia The mobility of our society and the distribution of industry and agriculture depend on an available supply of clean water; never- theless instances of groundwater contamination have been found in most sections of the country (Kerns, 1977; U.S. Environ- mental Protection Agency (U. S. EPA), 1980a]. For the purpose of this chapter, groundwater contamination will be defined as the addition of elements, compounds, and/or pathogens to water that alter its composition. One of the major difficulties with groundwater contamination is that it occurs underground, out of sight. The pollution sources are not easily observed nor are their effects often seen until damage has occurred. There are no obvious warning signals such as fish kills, discoloration, or stench that typically are early indicators of surface-water pollution. Where contamination af- fects pumping wells, some indications may occur, although many commonly found contaminants are both colorless and odorless and occur in low concentrations. The tangible effects of groundwater contamination usually come to light long after the incident causing the contamination has occurred. This long lag time is a major problem. Groundwater can be contaminated by a variety of com- pounds, both of natural origin and man-made. Contamination due to man has occurred for centuries, but industrialization, urbanization, and increased population have greatly aggravated the problem in some areas. A contaminant usually enters the groundwater system from the land surface, percolating down through the aerated soil and unsaturated (vadose) zone. The root zone may extend 2 or 3 ft into the soil, and many reductive and oxidative biological pro- cesses take place in this zone that may degrade or biologically change the contaminants. Plant uptake can remove certain heavy metals; microbial fixation and other biological processes can 23 also remove a fraction of the contaminants the size of the fraction being dependent on the nature of the contaminant. Deeper below the root zone, which consists mainly of humus and weathered rocks, there is a reduction in such biological processes. Attenuation may occur by surface adsorption, cat- ions in the contaminant being attracted to the negative charge on clay particles. Soils have a cation exchange capacity. Other contaminants may be removed by complexing with insoluble organic matter, which gives rise to complexed humic acids. Microbial action may influence redox potentials and cause the release of inorganic ions during decomposition (Braids, 1981). The susceptibility of different contaminants to differential at- tenuation varies. Once in the aquifer, a contaminant will move with the groundwater at a rate varying between a fraction of an inch to a few feet per day, forming, under certain idealized conditions, an elliptical plume of contamination with well-defined bound- aries. This dispersion process causes a spreading of the solute in a longitudinal flow direction and also transverse to the flow path (Chapter 2; Freeze and Cherry, 1979~; thus the plume will widen and thicken as it travels. Attenuation of the con- taminants in the aquifer may take place through dilution, vol- atilization, mechanical filtration, precipitation, buffering, neu- tralization, and ion exchange. Diffusion and dispersion will bring contaminants into contact with material that may retard their progress; thus attenuation may vary with the time and distance traveled. Unless the plume is blocked it will usually reach points of groundwater discharge such as streams, wet- lands, lakes, and tidal waters (Miller, 1981~. The shape of the plume will vary according to the continuity and duration of the source of contamination. Dispersion tends to dilute the con- taminants; however, concentrations of contaminants are typi-

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24 cally much higher in groundwater than in surface water (Miller, 1981). Groundwater is a major natural resource in the United States and is often more easily available than surface water. Between 40 and 50 percent of the population depends on groundwater as its primary source of drinking water (U. S. Water Resources Council, 1978a; U.S. EPA, 1977~. Groundwater delivered by community systems supplies 29 percent of the population, and a further 19 percent has its own domestic wells. About 95 percent of the rural population is dependent on groundwater for drinking purposes. Approximately 75 percent of American cities derive all or some of their supplies from groundwater (Leopold, 1974~. The states vary in their dependence on groundwater. Approximately 92 percent of New Mexico's pop- ulation uses groundwater for drinking water as compared with 30 percent of Maryland s population (U.S. EPA, 1977~. West of the Mississippi, in the area where irrigated agriculture is prevalent, the states depend heavily on groundwater, whereas the humid eastern portions of the country are less dependent. In 1980 the fresh groundwater withdrawals for the United States totaled 88.5 billion gallons per day, of which 68 percent was used for agricultural irrigation (U.S. Geological Survey Water Information Service, unpublished data). SOURCES OF GROUNDWATER CONTAM INATION There are three main ways in which the chemical composition of groundwater may be changed. The first is due to natural processes. Mineralization can result from leaching, especially in arid areas. Evapotranspiration can further concentrate salts in the remaining water. In the arid southwest and southcentral areas of the United States, natural leaching has been identified as the most prevalent source of contamination (Fuhriman and Barton, 1971; Scalf et al., 1973~. Chlorides, sulfates, nitrates, fluoride, and iron commonly occur in localized deposits, and their concentration in groundwater may exceed U.S. EPA standards. Arsenic and radioactivity from uranium ore also may cause local problems. The second category of sources of contamination is that due to man's waste-disposal practices. The 1977 Report to Congress on waste-disposal practices and their effects on groundwater (U.S. EPA, 1977) provided estimates of the sources and the extent of groundwater contamination. At the time the report was compiled, definitive data on waste-disposal practices often were not available, and indeed this is frequently the case today. Implementation of the Resource Conservation and Recovery Act of 1976 would be expected to affect waste-disposal prac- tices, but such recent data or estimates are not available. Sources of contamination involve all aspects of our lives, including man- ufacturing and service industries, agriculture, and government. It is estimated that over 30,000 chemicals are now being used and distributed through the environment and that an additional 1000 are being added each year (Weimar, 1980~. Besides the 1977 Report to Congress, a report by the Environmental As- sessment Council of The Academy of Natural Sciences of Phil- VERONICA I. PYE and JOCELYN KELLY adelphia (Pye et al., 1983) assessed the various sources of groundwater contamination. Contaminant sources from waste- disposal practices include individual sewage-disposal systems; land disposal of solid wastes; collection, treatment, and disposal of municipal wastewater; industrial and other wastewater im- poundments; land spreading of sludge; brine disposal associ- ated with the petroleum industry; disposal of mine wastes; deep-well disposal of liquid wastes; disposal of animal feedlot waste; and disposal of high- and low-level radioactive wastes resulting from a variety of activities. All of these potential sources of contamination are direct effects resulting in natural and syn- thetic substances entering the groundwater because of human activities (Matthess, 1982~. The third category of sources is also the direct result of human activities but is unrelated to waste-disposal practices. It includes accidental spills and leaks, agricultural activities, mining, highway de-icing salts, atmospheric contaminants and acid rain, surface water, improperly planned groundwater de- velopment leading to saltwater intrusion, and improper well construction and maintenance. Groundwater pollution problems and their sources have been the object of numerous studies. An incomplete, but illustrative, listing would include Fuhriman and Barton (1971), Scalf et al. (1973), Miller et al. (1974), van der Leeden et al. (1975), Keeley (1976), Miller et al. (1977), U.S. EPA (1978a, 1978b, 1980a), U.S. General Accounting Office (1978, 19807; U.S. Water Re- sources Council (1978a, 1978b, 1978c), Jackson (1980), and Pye et al. (1983~. SEVERITY OF GROUNDWATER CONTAMINATION In determining the overall magnitude of the national problem, defining severity poses some difficulty. The definition may be approached in several ways. If the contaminants in the groundwater exceed the interim standards set for drinking water, then the problem could be said to be severe, depending on the extent to which the con- tamination exceeds the standard, if the intended use is for drinking water. If the groundwater was not intended for drink- ing, then the problem need not be severe. It should be noted that the interim standards do not cover the many synthetic chemicals that can often be found in water. (See proposed rulemaking for volatile synthetic organic chemicals published in the Federal Register, March 4, 1982.) The number of persons affected by contamination might be taken into account. Thus the contamination of an aquifer in the vicinity of a municipal well field would be of more concern than contamination occurring in an isolated, sparsely populated area. In terms of a single aquifer, the severity of contamination may be related to the percentage of the aquifer contaminated by point or nonpoint sources. Nationwide, the severity of the problem may be indicated by the percentage of the available groundwater that is affected.

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The Extent of Groundwater Contamination A different measure of severity might be obtained if the volume of known and suspected contaminated plumes of groundwater is expressed as a percentage of the nationwide groundwater reserves. The degree of hazard posed by the contaminants varies according to the volume discharged, toxicity, persistence, and concentration and would be affected by how the contaminants move in the aquifer. Thus severity could depend on one or a combination of the following parameters: concentration, persistence, and toxicity of the contaminants; the number of people affected if the con- taminated aquifer is a source of drinking water; and the per- centage of the available groundwater (both locally and region- ally) affected by such contamination. Interwoven with each of these factors would be the economic cost of finding an alter- native source of water if the contamination renders the ground- water unfit for its previous or future uses or if treatment of the water before use is not possible. Many of the data required for these methods of assessing severity of contamination in quantitative terms simply are not available. The U. S. EPA (1980b) in the appendixes to the plan- ning workshops to develop recommendations for a groundwater protection strategy accurately summarized the sort of infor- mation that is available from existing reports and studies, namely documentation of a large number of contamination incidents, identification of important sources of contamination, deter- mination of the mechanisms of contamination, in-depth studies of some contamination incidents, and surveys of the number of certain contamination sources nationwide. The U.S. EPA (1980a) recognized the usefulness of conducting a nationwide survey at randomly selected sites to obtain an estimate of con- tamination but ruled out this possibility because of the expense of drilling and water sampling and the long time required. Instead the U. S. EPA adopted a second approach of estimating the number of sources of contamination and the amount of contamination per source. The agency obtained an order-of- magnitude estimate of the extent of the problem and utilized existing information, both qualitative and quantitative. Such assessments serve a useful purpose but only when their in- herent flaws are kept in mind. Using information and estimates for only two sources of contamination landfills and surface impoundments and whether they are sited over usable aqui- fers, the length of time they have been operating, and the volume of available groundwater in storage, the U.S. EPA (1980b) estimated that between 0.1 and 0.4 percent of the usable "surface" aquifers are contaminated by industrial im- poundments and landfill sites. The U.S. EPA cautioned that this is a nationwide estimate and that the two types of disposal sites used are usually found in areas of significant industrial and domestic water use and that the problem could be exac- erbated by the area's dependence on groundwater. The U.S. EPA, although considering landfills and impoundments to be the most important sources, also evaluated secondary sources such as subsurface disposal systems (septic tanks) and petro- leum exploration and mining and concluded that such sources had contaminated about 1 percent and 0.1 percent, respec- 25 lively, of the nation's usable aquifers. The U.S. EPA (1980b) therefore concluded that at present nearly 1 percent by area of the usable "surface" aquifers in the United States may be contaminated by these four activities and that the areas of contamination will increase with time. It did not include an estimate of the percentage of available groundwater contami- nated by man's activities unrelated to waste disposal. Lehr (1982) recently completed another independent esti- mate, assuming a total of 200,000 point sources. Using faster rates of contaminant spread over a longer period of time, Lehr considered this to be a "worst-case" estimate. He arrived at a range of between 0.2 and 2 percent. He concluded by stating that no matter how liberal or conservative the estimate, the fraction of polluted groundwater is small. This raises the ques- tion of how to determine the salience of the problem. Should contamination of 1-2 percent of our usable "surface" aquifers be considered a minor or a serious problem? Obviously, for those immediately affected, it is a serious problem. Also there are many regions where the contamination could exceed 2 percent as the contamination is not uniform geographically. Lehr (1982) optimistically predicted that the initiation of new sources of pollution from waste disposal could be eliminated in 10 yr by careful siting and facility design and operation and that by taking these steps 98 percent of our available ground- water could remain unpolluted. However, this does not mean that existing sources will not continue to produce contamina- tion. Little information is readily available concerning the size of the population affected by well closings due to groundwater contamination. There are well-documented cases of well clos- ings in South Brunswick, New Jersey (Geraghty and Miller, Inc., 1979~; New Castle County, Delaware (Frick and Shaffer, undated); and Long Island, New York, and California (Council on Environmental Quality, 1981~. About 3 million people have been affected by well closings, both municipal and domestic, in these four states alone. Thus at present it is difficult to make useful judgments on the severity of groundwater contamination based on the number of people affected. The types of chemicals that emanate from anthropogenic sources of contamination are varied. They range from simple inorganic ions such as nitrate (from septic tanks, feedlots, and fertilizer use>, chlorides (from highway de-icing salt, saltwater intrusion, certain industrial processes), radioactive materials and heavy-metal ions (e.g., chromium from plating works) to complex organic compounds resulting from manufacturing and industrial activities and some of which are found in household cleaning fluids. The chemical composition of wastes deposited in landfills or surface impoundments is often known. Never- theless when the constituents of such wastes interact, new compounds may be formed that would not appear on the orig- inal waste content inventory. Many industrial waste-disposal practices involve stabilization of waste, thereby rendering it less chemically active, but leachate production may still alter some of these chemicals. The degradation of contaminants by microbial organisms in the soils also changes the chemical com- position, thus making it almost impossible to predict precisely what contaminants reach the aquifer.

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26 REGIONAL ASSESSMENTS OF GROUNDWATER CONTAMINANTS IN THE UNITED STATES In the 1970s the U.S. OPT ^~i~i^~1 fifth '-=i^~1 O~e ~ ~ ~ ~ ~V1111111~1~11~ 11 V ~ 1 ~~AVI1~1 "~O ~ ~ ~ . .^ ment reports. They summarized the geology, major aquifers, natural groundwater quality, and major pollution problems for each region. The reports were completed for Arizona, Califor- nia, Nevada, and Utah (Fuhriman and Barton, 1971), the south- central states (Scarf et al., 1973), the Northeast (Miller et al., 1974), the Northwest (van der Leeden et al., 1975), and the Southeast (Miller et al., 1977~. Three additional reports were to have covered Alaska and Hawaii, the Great Lakes area, and the northcentral region, but these were not completed. The findings for the principal sources of contamination in the five VERONICA I. PYE and JOCELYN KELLY regions are shown in Table 1.1. The assessment of the relative importance of the sources of contamination may have changed recently owing to a greater knowledge of the occurrence of toxic organic chemicals in groundwater. Nevertheless, at the time the U.S. EPA reports were completed, contamination resulting from natural processes unrelated to man's activities was considered to be of most concern in the arid southcentral and southwestern states. The extensive irrigation that trans- formed parts of the Southwest into a major crop-producing area was considered to have caused problems from irrigation return flow. Such problems would involve an increase in nitrate con- centrations from fertilizer use, an increase in pesticide content, and leaching of salts. The slow rate of recharge of many of the aquifers in this area, coupled with extensive groundwater with- TABLE 1.1 Sources of Groundwater Pollution throughout the United States and Their Prevalence in Each Regiona Source Northeast Northwest Southeast Southcentral Southwest Natural Pollution Mineralization from soluble aquifers Water from fault zones, volcanic origin Evapotranspiration of native vegetation Aquifer interchange Groundwater Development Connate water withdrawal Overpumping/land subsidence Underground storage/artificial recharge 4 Water wells Saltwater encroachment Agricultural Activities Dryland farming Animal wastes, feedlots Crop residues, dead animals Pesticide residues Irrigation return flow Fertilization 1 4 3 4 4 4 4 4 3 3 2 2 16 2 1 4 3 2 2 2 3 3 4 1 4 4 1 2 Mining Activities 2 2 3 2 Waste Disposal Septic tanks/cesspools 1 1 2 2 1 Land disposal, municipal and 3 2 2 industrial wastes Landfills 1 3 1 Surface impoundments 2 1 3 Radioactive waste disposal 3 Injection wells 2 4 2 Disposal of oil-f~eld brines 1 1 Miscellaneous Accidental spills 2 3 1 3 2 Urban runoff 3 Highway de-icing salts 1 4 4 Seepage from polluted surface waters 3 4 3 Buried pipelines and storage tanks 1 Abandoned oil and test wells 1 Petroleum exploration and development 3 4 aNortheast includes NY, NJ, PA, MD, DE, and New England; southeast: AL, FL, GA, MS, NC, SC; northwest: CO, ID, MT, OR, WA, WY; southwest: AZ, CA, NV, UT; southeentral: AR, LA, NM, OK, TX. Reports not completed for Great Lakes and North Central regions, AK, and HI. Numbers indicate degree of contamination: 1, high; 2, medium high; 3, medium low; 4, low.

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The Extent of Groundwater Contamination drawals, has led to groundwater overdrafting and associated changes in groundwater quality and increased pumping costs. The southcentral region, the most important area for petroleum production, had a major problem with oil-field brines contam- inating groundwater. Because of their sheer numbers and den- sity, individual septic tank systems were considered the main cause for concern in the Northwest, Northeast, and Southeast. Contamination from septic tanks would result in elevated levels of nitrate. More recently, widespread use of septic tank clean- ers containing decreasing agents such as trichloroethylene has resulted in groundwater contamination by synthetic organic chemicals (Council on Environmental Quality, 19811. The U. S. EPA assessments further identified the importance in the Northeast and the Southeast of problems associated with in- dustrial development, namely leakage from buried pipelines and storage tanks and landfills and impoundments. Most of the U.S. EPA assessments were completed before the attendant publicity of Love Canal and the Valley of the Drums had made public the potential threat of such dump sites and thus spurred further investigations. All the reports were completed before the U. S. EPA's Surface Impoundment Assessment (U. S. EPA, 1978a) made available the number of such potential sources of contamination. Keeley (1976) concluded from the U.S. EPA regional as- sessments that problems indigenous in one area may not occur in another but that several sources of groundwater contami- nation occur at a high or moderate degree of severity in each area studied. He noted that the four pollutants most commonly reported were chlorides, nitrates, heavy metals, and hydro- carbons but that this may merely be a reflection of the moni- toring practices. Sampling for organic chemicals is not routine and is usually expensive, although these chemicals are almost always associated with municipal and industrial wastes. Keeley (1976) also made the point that the rank-ordered problems in the five regions were not selected on the basis of statistical information as such information was not available. The prior- ities were established empirically on the basis of the experience of the authorities and individuals who had worked in the five regions. STATE SUMMARIES OF KNOWN INCIDENCES OF CONTAMINATION Recent federally mandated surveys under the Safe Drinking Water Act have produced more information concerning the number of potential sites where groundwater contamination might occur (U.S. EPA, 1978b). In addition, many individual states have recently undertaken inventories of their ground- water contamination case histories. However, no systematic national sampling survey has been carried out, a necessary step for making an accurate appraisal and quantitative evaluation of the extent of contamination. The Environmental Assessment Council (Pye et al., 1983) conducted a survey in 1981-1982 of groundwater contamination incidents to investigate further whether additional information, collected over the last few years, could cast more light on groundwater problems in terms of severity and patterns of occurrence. Data were collected on known incidents of con- 27 lamination from all the states by contacting each state and requesting information on case histories of contamination if it was available. The information received varied in usefulness, some states having completed inventories and others having just started or still in the process of documentation. Several states were chosen to serve as examples in the report partly because they had the most information about case histories of groundwater contamination and because oftheir differing levels of industrialization, agricultural activity, population density, dependence on groundwater, and climatic conditions. The states chosen were Arizona, California, Connecticut, Florida, Idaho, Illinois, Nebraska, New Jersey, New Mexico, and South Car- olina. For the purpose of this assessment, the contaminants were divided by source rather than constituents as these were not always specified. Sources included industrial and manufactur- ing waste products, petroleum products, landfill leachate, chlo- rides, and organic wastes. Industrial and manufacturing prod- ucts and wastes may be liquid or solid. Wood processing plants were included in this category. Where the wastes were spec- ified as petroleum or its derivatives the case histories were included under that category. Petroleum products included home heating oil, aircraft fuel, and gasoline. Landfill leachate would be derived from solid, semisolid, or liquid waste of either municipal or industrial origin. Chlorides were usually desig- nated as originating from highway de-icing salts, agricultural return flow, oil field brines, and/or saltwater intrusion. Organic wastes included those, for example, derived from plant, animal, or human wastes and those from feedlots, dairy barns, fruit and vegetable processing plants, and sewage. The discovery of groundwater contamination is not an end in itself, and there are many remedial actions, direct and in- direct, that can be taken to alleviate or reduce the problem, even though these are often costly. Direct remedial actions include actual cleanup of a contaminated site by soil removal, pumping and treating contaminated water, or artificially re- charging a contaminated aquifer; preventing further spreading of contamination by building artificial barriers; and eliminating sources of contamination by removing the contaminants or clos- ing dumping sites. Indirect remedial actions include monitor- ing, providing new water supplies, taking legal action, and installing filtering mechanisms to keep contaminants out of the water supply. It should be emphasized that the case histories used in this survey only indicate the potential magnitude of the problem rather than the actual magnitude. Because the information deals only with specific incidents, it usually only provides an indi- cation of the range and importance of point sources but not of all nonpoint sources. Where point sources were documented and known to be of importance, an analysis of them is also given. Arizona Arizona uses 4800 million gallons per day (mad) of groundwater, which is 61 percent of its total water use (Fuhriman and Barton, 1971~. The state is divided into five groundwater basins: the Upper and Lower Santa Cruz, White Mountain, Salt River

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28 Valley, and Upper Salt River Basins (Arizona Division of En- vironmental Health Services, 1979~. The Upper and Lower Santa Cruz Basins and the Salt River Y alley all comprise an area known as the Basin and Range Lowlands Province, where the two major population centers of Arizona are located Tuc- son and Phoenix. This area uses the most groundwater in the state and has the highest potential for contamination. Few cases of groundwater contamination are known to have occurred a total of 23 incidents (Arizona Division of Envi- ronmental Health Services, 1979; Hadeed, 1979; Lemmon, 1980; Robertson, 1975; Schmidt, 1972; U.S. EPA, 19811. All of them threatened or affected the water supplies. The most common source of contamination was industrial wastes (7 cases) closely followed by landfill leachate (6 cases) and human and animal wastes (6 cases). Each of the incidents involving human and animal wastes led to outbreaks of disease. The incidents were discovered, for the most part, by investigation, and in only 6 of the cases was some sort of remedial action taken. California California uses more groundwater than any state in the na- tion approximately 13,390 mad (California Department of Water Resources, 1975~. Groundwater supplies about 40 per- cent of the state's water needs. The largest groundwater res- ervoir underlies the Central Valley Region, which occupies 10 percent of California's land area and includes the San Joaquin Valley (Thomas and Phoenix, 1976~. Overall groundwater quality is considered good and bene- ficial for all uses (California Department of Water Resources, 1975~. There is no readily accessible complete inventory of case histories of groundwater contamination available in California, but some information on general and persistent contamination problems in the state will be summarized. The data often do not refer to specific cases of contamination but to generalized occurrences. Six general statewide groundwater problems of present or potential concern have been identified (California State Water Resources Control Board and Regional Water Quality Control Boards, 1980~: 1. Increasing nitrate concentrations from various sources are a current problem in some areas and a potential problem in other areas. Animal wastes are one potential source of nitrate contamination. In 1968, beef plus dairy cattle numbered almost 1,900,000 head, most being fed on the open range (Fuhriman and Barton, 1971~. Poultry numbered 260 million, and the hog population was 150,000 head. 2. Groundwater overdrafting has resulted in seawater intru- sion of the 262 coastal groundwater basins (Fuhriman and Bar- ton, 1971), mineralization due to recirculation or percolation of used, and induced connate water migration. In the Los Angeles area, three barriers have been constructed against seawater encroachment. Overdrafting has also resulted in land subsidence, which has been most severe in the San [oaquin Valley, where subsidence in excess of 20 feet has occurred in some areas (Fuhriman and Barton, 1971~. VERONICA I. EYE and JOCELYN KELLY 3. Lack of officially designated hazardous-waste dump sites has resulted in illegal dumping. Many rubbish sites are not up to regulation. Fuhriman and Barton (1971) identified 207 legal sites with inadequate control over surface drainage. 4. Percolation ponds for handling industrial and military wastes are often inadequate for the types of wastes being disposed. Oil-field brines and brines from water softener regeneration plants are particularly troublesome (California Department of Water Resources, 1975~. 5. Crop dusting operations have resulted in numerous sources of pesticides having potential to reach groundwater. 6. The design of proper monitoring wells may be the biggest roadblock to the process of establishing waste-discharge re- quirements. Connecticut Connecticut uses little groundwater to meet its freshwater needs 116 mad representing 8.2 percent of its total water use (Handman et al., 1979~. Nearly one third of the ground- water used (34.2 mad) goes for public and municipal supply; the rural domestic or private well supply comes entirely from groundwater, about 49.0 mad; 30.8 mad is used by industry. The remaining 1.2 mad is used for livestock, irrigation, and miscellaneous uses. Connecticut provided details of 64 cases of groundwater con- tamination (Miller et al., 1974; Lindorff and Cartwright, 1977; Handman et al., 1979; Handman and gingham, 1980; U.S. Congressional Research Service, 1980; U.S. EPA, 1981), 37 (58 percent) of which affected the water supplies. In addition, Rolston et al. (1979) mapped 450 wells known to have produced contaminated water, and Miller et al. (1974) reported that "sev- eral dozen" wells were contaminated by saltwater intrusion in the Long Island Sound area. The main reported or known contamination problem stems from industrial or manufacturing products and wastes, which account for 44 percent of the cases. The primary means of detection was by well contamination. No remedial action was reported for over 70 percent of the cases. Florida Florida is a major user of groundwater, requiring more than 3000 mad in 1975 representing 18 percent of its total water use. In 1970, groundwater use was 760 mad for public water supply, 180 mad for rural uses, 1300 mad for irrigation, and 710 mad for industrial uses (Miller et al., 1977~. Florida recently completed an inventory of its known cases of groundwater contamination, and 92 cases were reported (Miller et al., 1977; Florida Department of Environmental Reg- ulation, 1980, 1981a, 1981b; U.S. EPA, 1981~. Of these, 63 percent affected or threatened water supplies. In fact, 50 per- cent of the cases were discovered via contamination of wells. The most important sources of groundwater contamination are chlorides from saltwater intrusion and agricultural return flow and industrial/manufacturing products or wastes, which ac- counted for a total of 72 percent of the cases. Of all the cases,

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The Extent of Groundwater Contamination 29 only 35 percent of them have had any kind of remedial action Fifty-eight cases of contaminated groundwater have been applied. At the time these date were supplied, Florida was still documented for Illinois (Walker, 1969; Lindorff and Cart- in the documentation phase of assessing its reported incidents of groundwater contamination. Idaho In 1975, Idaho used 5600 mad of groundwater, representing 31 percent of the total water used in that state (Lehr, 1981~. Fourteen percent of the total groundwater used in Idaho goes to irrigation (van der Leeden et al., 1975~. There are relatively few documented case histories of groundwater contamination in Idaho (van der Leeden et al., 1975; Lindorff and Cartwright, 1977; U.S. EPA, 1978a, 1981) but several potential sources of contamination to be concerned about. At the Idaho National Engineering Laboratory (INEL), located in the eastern part of the Snake River Plain, liquid- waste-disposal practices are constantly monitored, and, as of 1975, only strontium-90 has exceeded the maximum standard for drinking water (van der Leeden et al., 1975~. The majority of radionuclides disposed of at INEL have short half-lives and are of no consequence. Mining is another potential source of contamination. Large-scale mining goes on for silver, lead, zinc, sand and gravel, and stone. There are 11 abandoned coal mines, 1749 abandoned metal mines, and 208 abandoned non- metal mines. The extensive agricultural industry in Idaho pre- sents several potential contamination hazards. Fertilizers and pesticides are used in large quantities. Dieldrin, now banned but once used heavily for the control of Weiss worm in potatoes, still persists in the soil. In 1973, there were 563 feedlots mostly located along the Snake River. There are at least 5000 domestic and agricultural waste-disposal wells all located in the Snake River Plain. A few cases of serious contamination from waste- disposal wells have resulted because of the high permeability of the aquifer. Of the 29 known incidents, the majority (14 or 48 percent) are due to contamination from human and animal organic wastes. Industrial and radioactive wastes combined ac- count for 24 percent of the cases. Of the incidents, 62 percent actually affected the water supplies and 34 percent threatened them. Thirty-one percent of the contamination incidents re- sulted in or posed the threat of outbreaks of disease. The means of detection was usually by well contamination or by investi- gation. In 55 percent of the cases no mention was made of any remedial action that has been taken. Illinois In Illinois, groundwater is the freshwater source for approxi- mately 1600 public water-supply systems and the principal source for industry, agriculture, and almost all private water- supply systems in the state (Gibb and O'Hearn, 1980~. The state used about 1000 mad of groundwater in 1978, which accounted for about 8 percent of total freshwater use. In 1970, 38 percent of the entire state population and 82 percent of the rural population were dependent on groundwater as a drinking source (Piskin et al., 1980~. ~ 7 ~ wright, 1977; Piskin et al., 1980; U.S. Congressional Research Service, 1980; U.S. EPA, 1981~. Of the known incidents of groundwater contamination, 44 of them (76 percent) affected or threatened the water supplies. The most prevalent source of contamination is from animal and human wastes (20 cases or 34 percent) followed by industrial waste and landfill leachate (21 and 28 percent, respectively>. Groundwater from shallow wells often has large concentrations of nitrate. Eighty-one per- cent of the dug water wells, less than 50 feet deep, contained in excess of the standard of 10 mg/L of NO3-N2, as opposed to 34 percent of the deeper drilled wells in Washington County (National Research Council, 1977~. All the incidents involving contamination from animal or human wastes affected or threat- ened the water supplies. The majority of incidents (45 or 78 percent) were detected by well contamination, investigation, and outbreaks of illness. Illinois has a good record for applying remedial actions, as 66 percent of the incidents have received some sort of action. There are no documented cases of groundwater contami- nation from waste-injection wells, but they are potential haz- ardous sources of contamination (Ford et al., 1981~. In Illinois, there are 9 Class I wells (the deepest variety, injecting below the deepest underground source of drinking water) and 17,167 Class II wells, which are oil- and gas-related, enhanced-recov- ery, brine-injection, and liquid-hydrocarbon storage wells. Nebraska This predominantly agricultural state uses nearly twice as much groundwater as Florida, 5900 mad or 68 percent of its total water supply (Lehr, 1981~. Most of this is supplied by the extensive Ogallala Aquifer, which underlies parts of Texas, New Mexico, Oklahoma, Kansas, Colorado, Nebraska, Wyoming, and South Dakota. Of the 35 incidents of contamination from point sources, 34 percent threatened or affected the water supplies (Engberg and Spalding, 1978; Spalding et al., 1978a, 1978b, 1979; Exner and Spalding, 1979; Gormley and Spalding, 1979; Junk et al., 1980; Nebraska Department of Environ- mental Control, 1980a, 1980b, 1981; Spalding and Exner, 1980; University of Nebraska, 1980; U.S. EPA, 1981~. Incidents in- volving pesticides and fertilizers accounted for 43 percent of the cases, but these compounds are also involved in nonpoint- source contamination. The second most prevalent sources of contamination are plant, animal, and human wastes, accounting for 31 percent. Most of the incidents were discovered following investigation, and in 74 percent of the cases no remedial action was reported. Various surveys in Nebraska sampled 4350 wells and found that 700 contained NO3-N2 contamination in excess of the standard of 10 mg/L. Studies showed that of the contaminated wells 575 (82 percent) were contaminated by nonpoint sources such as nitrogen fertilizer contained in irrigation return flow. Septic tanks, barnyards and feedlots, and point sources ac- counted for the remaining 18 percent.

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30 New Jersey New Jersey, one of the most densely populated regions in the United States, has more than 16,000 potable wells (Tucker, 1981~. Sixteen percent of the drinking water is derived from underground sources. In the southern half of the state, more than 90 percent of the population receives its drinking supply from groundwater. In 1976 it was estimated that 406 mad of groundwater went to public supply, 75 mad to rural supply, 118 mad to industry, and 53 mad to irrigationa total of 652 mad or 54 percent of the total freshwater supply used in New Jersey. In 1981 New Jersey completed an extensive sampling of its groundwater aquifers for toxic chemical contamination and, in addition, compiled a comprehensive inventory of groundwater contamination cases 374 incidents (New Jersey Department of Environmental Protection, 19817. The aquifer samples for chemical analysis were collected from a random sampling of wells throughout the state a sampling, however, designed to cover all the different areas. Where problems were found, additional investigations of potential sites of contamination in the same area were conducted. The contamination inventory lists all known groundwater pollution in the state but may be incomplete owing to the occurrence of new cases. The most numerous incidents are those involving industrial wastes and petroleum products, which accounted for 40 and 39 percent of the cases, respectively. Pesticides account for few of the cases, even though New Jersey is both an industrial and agricultural state. In 41 percent of the cases some form of remedial action has been taken; in 48 percent, remedial action is being con- sidered or a monitoring program has been started. New Mexico Groundwater provided 49 percent of New Mexico's water in 1970; 85 percent of the groundwater withdrawals were used for irrigation (S calf et al., 19737. In 1975, groundwater usage increased slightly, accounting for 50 percent of the total water usage or 1600 mad. Groundwater quality is threatened by overpumping in the eastern part of the state; mining for uranium, copper, molyb- denum, and potash in various areas throughout the state; and oil production in the northeastern and southwestern parts of the state. There have been 105 reported incidents of groundwater con- tamination in New Mexico (New Mexico Environmental Im- provement Division, 1980; U.S. EPA, 1981~. Most are cases of chloride contamination from oil-field brines (40 cases). Of these cases, 36 affected water supplies. Animal and human wastes accounted for 31 cases, 28 of which resulted in contam- inated drinking water supplies. Mine wastes also accounted for 14 incidents. Only 6 percent of the total reported incidents caused adverse public health effects. The majority of incidents were discovered by contamination of well water. Fewer than 30 percent of the cases of groundwater contamination men- tioned that any remedial action had been taken. VERONICA I. PYE and JOCELYN KELLY South Carolina In 1970, 61 percent of the total population of South Carolina relied on groundwater for their drinking water supply (Scarf et al., 1973), and groundwater accounted for 23 percent of the total water usage from all sources. Lehr (1975>, however, showed that in 1975 only 3 percent of the total use was attributable to groundwater. Total groundwater usage in 1975 was 200 mad. There are 89 known cases of groundwater contamination (South Carolina Department of Health and Environmental Control, 1980, 1981~. Petroleum products are involved in the majority of incidents, 43 cases (48 percent), of which 88 percent affected the water supply. Contamination by industrial wastes ac- counted for 28 of the incidents (31 percent), of which half threatened or affected the water supply. More than half the cases were detected by well contamination. For the majority of incidents (89 percent) remedial action was under consider- ation, monitoring had been started, or no remedial action was mentioned. SUMMARY AND CONCLUSIONS The summaries of groundwater pollution sources completed by the U.S. EPA (Table 1.1) and the Environmental Assess- ment Council (EAC) (Table 1.2) show that contamination prob- lems from several sources have been reported from all parts of the United States and that the problems vary from one region to another, depending on climate, population density, intensity of industrial and agricultural activities, and the hydrogeology of the region. A comprehensive national survey might well uncover other important sources of contamination or different frequencies of the same sources. Neither the U.S. EPA nor the EAC summaries can be considered complete as they do not result from comprehensive national surveys. It is difficult to estimate severity from these summaries as there is no es- tablished method for doing so. Essentially the information con- tained in the EAC state summaries presents a"best-case" sce- nario; the situation can only change as new cases of contamination are discovered. The important sources of contamination identified in the EAC state summaries (Table 1.2) differ somewhat in order of importance from those identified by the U.S. EPA summaries (Table 1.1) partly because the EAC summarized information from individual states whereas the U. S. EPA did regional sum- maries and because the methods of assessment were different. The U.S. EPA summaries are empirical assessments relying on the expertise of professionals who had worked in the regions studied If. W. Keeley, Kerr Environmental Research Labo- ratory, personal communication, 19821. Data for the EAC state summaries were based on anecdotal reports of case histories supplied by state agencies, and the categories for types of con- taminants are fewer and broader than those in the U.S. EPA surveys. Some generalizations can be made from the combined results of the two surveys. It is clear that human and sometimes animal wastes are a high-priority source of contamination throughout

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The Extent of Groundwater Contamination 31 TABLE 1.2 Most Frequently Reported Sources of Groundwater Contamination in the Ten States Reviewed by the Environmental Assessment Councila % For Which Total Number Remedial Natural of Known % Affecting Actions Groundwater Quality of Most Frequently Reported Contamination or Threatening Have Been Use, mgdb Groundwaterc Sources of Contamination Incidents Water Supply Undertaken . Arizona Connecticut 1 16 4800 Generally good; mineralization problems 13400-19000 Good Good to excellent Florida 3000 Generally good Idaho 5600 Good Illinois 1000 Generally good Nebraska 5900 Generally good New Jersey 790 Generally good New Mexico 1500 South Carolina 200 Fair to good; mineralization problems Suitable for most uses 1. Industrial wastes 2. Landfill leachate 3. Human and animal wastes . Saltwater intrusion 2. Nitrates from agricultural practices 3. Brines and other industrial and military wastes 1. Industrial wastes 2. Petroleum products 3. Human and animal wastes 1. Chlorides from saltwater intrusion and agricultural return flow 2. Industrial wastes 3. Human and animal wastes 1. Human and animal wastes 29 97 45 2. Industrial wastes 3. Radioactive wastes 1. Human and animal wastes 58 76 70 2. Landfill leachate 3. Industrial wastes 1. Irrigation and agriculture 2. Human and animal wastes 3. Industrial wastes 1. Industrial wastes 2. Petroleum products 3. Human and animal wastes 1. Oil-field brines 2. Human and animal wastes 3. Mine wastes 1. Petroleum products 2. Industrial wastes 3. Human and animal wastes 23 100 26 Not known Not known Not known 64 59 30 92 63 39 35 34 26 374 50 41 105 83 29 89 74 45 aPye et al. (1983). Leer (1981). Ivan der Leeden et al. (1975), Miller et al. (1974, 1977), Fuhriman and Barton (1971), and Scalf et al. (1973) the country. In the EAC survey, human and animal wastes are among the top three contaminants in every state surveyed except California (for which individual cases were not avail- able). Human wastes are ranked as highest-priority contami- nants in three of the regions surveyed by the U.S. EPA Northeast, Northwest, and Southwest. They are of medium- high priority in the southeastern and southcentral regions. In- dustrial wastes are also common and high-priority contaminants in most regions of the country. In the Northeast, both surveys show industrial waste disposal as the biggest source of ground- water contamination. In the southeastern (Florida, South Car- olina) and northwestern (Idaho) states surveyed by EAC, in- dustrial wastes are the second most prevalent contaminants of groundwater, which concurs with the U. S. EPA regional sur- vey. And in the northcentral states (Illinois, Nebraska), where agricultural activities are important, industrial wastes are ranked third in reported frequency of contamination. In the south- western (Arizona, California) and southcentral (New Mexico) states, disposal of oil-field brines accounts for a high percentage of industry-related contamination. Land disposal of general in- dustrial wastes is of secondary importance. Beyond industrial wastes and human and animal wastes, the sources of contamination vary considerably from one region of the country to another depending on the intensive activities of a particular state (e.g., mining, agriculture, industry) and the geographic and geologic location of the state (some coastal states have severe problems with saltwater intrusion into ground- water; states located in snowbelts have problems with chloride

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32 contamination from road salts; states having soluble aquifers have problems with mineralization). The major sources of con- tamination are nearly all induced by human activity, apart from naturally poor quality water caused by dissolution of natural compounds in the strata through which groundwater flows. Although contamination of groundwater has occurred throughout the United States, and is likely to continue to some extent in the future, we are still in a position to make choices on how best to use, manage, and protect this valuable resource. REFERENCES Arizona Division of Environmental Health Services (1979). Arizona Surface Impoundment Assessment Ground Water Contamination Cases, 47 pp. Braids, O. C. (1981). Behavior of contaminants in the subsurface, in Seminar on the Fundamentals of Ground Water Quality Protection, presented by Geraghty and Miller, Inc., and American Ecology Services, Inc., Cherry Hill, N.J., October 5-6. California Department of Water Resources (1975). California's ground water, California Department of Water Resources Bulletin 118. California State Water Resources Control Board and Regional Water Quality Control Boards (1980). Water Quality/Water Rights: 1978- 80 Report. Council on Environmental Quality (1981). Contamination of Ground Water by Toxic Organic Chemicals, Washington, D.C., 85 pp. Engberg, R., and R. F. Spalding (1978). Ground water quality atlas of Nebraska, Resource Atlas No. 3, University of Nebraska Lin- coln, 39 pp. Exner, M. E., and R. F. Spalding (1979). Evolution of contaminated ground water in Holt County, Nebraska, Water Resour. Res. 15, 139-147. Florida Department of Environmental Regulation (1980). Florida Sur- face Impoundment Assessment: Final Report, Tallahassee, Fla., 298 PP Florida Department of Environmental Regulation (1981a). Hazardous Waste Inventory, Tallahassee, Fla., 59 pp. Florida Department of Environmental Regulation (1981b). Summary of Known Cases of Ground Water Contamination in Florida, Tal- lahassee, Fla., 12 pp. Ford, M., R. Piskin, M. Hagele, R. Strom, and J. Dickman (1981). Inventory and Preliminary Assessment of Class I and Class 11 In- jection Wells in Illinois, State of Illinois Environmental Protection Agency, Div. of Land/Noise Pollution Control, 111 pp. Frick, D., and L. Shaffer (undated). Assessment of the availability, utilization, and contamination of water resources in New Castle County, Delaware, Department of Public Works, Office of Water and Sewer Management, New Castle County, Delaware (for U.S. EPA Office of Solid Waste Management Programs, Contract No. WA-6-99-2061- J), 215 pp. Freeze, R. A., and J. A. Cherry (1979). Ground Water, Prentice-Hall, Inc., Englewood Cliffs, N.J., 604 pp. Fuhriman, D. K., and J. R. Barton (1971). Ground water pollution in Arizona, California, Nevada, and Utah (Report #1600ERU for the Office of Research and Monitoring, U.S. EPA), 249 pp. Geraghty and Miller, Inc. (1979). Investigations of Ground Water Con- tamination in South Brunswick Township, N.J., Geraghty and Miller, Inc., Syosset, N.Y., 49 pp. Gibb, J. P., and M. O'Hearn (1980). Illinois ground water quality data summary, prepared by Illinois State Water Survey (for the Illinois VERONICA I. EYE and JOCELYN KELLY Environmental Protection Agency, Contract No. 1-47-26-84-353-00), 60 pp. Gormley, J. R., and R. F. Spalding (1979). Sources and concentrations of NO3-nitrogen in ground water of the Central Platte region, Ne- braska, Ground Water 17, 291-300. Hadeed, S. J. (1979). DBCP Well Sampling Program for Yuma County, Arizona (7 June-26 July 1979), Arizona Dept. of Health Services, Phoenix, Ariz., 33 pp. Handman, E. H., and J. W. gingham (1980) Effects of Selected Sources of Contamination on Ground Water Quality at Seven Sites in Con- necticut, U.S. Geol. Surv. Open File Rep. 76-1596, 63 pp. Handman, E. H., I. G. Grossman, J. W. gingham, and J. L. Rolston (1979). Major Sources of Ground Water Contamination in Con- necticut, U.S. Geol. Surv. Open File Rep. 79-1069, 59 pp. Jackson, R. E., ed. (1980). Aquifer contamination and protection, Proj- ect 8.3 of the International Hydrological Programme, UNESCO, Paris, France, 440 pp. Junk, G. A., R. F. Spalding, and J. J. Richard (1980). Areal, vertical, and temporal differences in ground water chemistry, II. Organic constituents, J. Environ. Qual. 9, 479-483. Keeley, J. W. (1976). Ground water pollution problems in the United States, in Proceedings of a Water Research Conference, "Ground Water Quality, Measurement, Prediction and Protection." Kerns, W. R., ed. (1977). Public policy on ground water protection, in Proceedings of a National Conference, April 13-16, Virginia Po- lytechnic Institute and State University, Blacksburg, Va. Lehr, J. H. (1975). Ground water pollution problems and solutions, water pollution control in low density areas, in Proceedings of a Rural Environmental Engineering Conference, W. J. Jewell and R. Swan, eds., University Press of New England, Hanover, N.H. Lehr, J. H (1981). Groundwater in the eighties, Water and Engineering Management 123(3), 30-33. Lehr, J. H. (1982). How much ground water have we really polluted? (editorial), Ground Water Monitoring Rev. (Winter), 4-5. Lemmon, J. (1980). Drums along the Salt, in Proceedings of the Arizona Section of the American Water Resources Association Symposium on Water Quality Monitoring and Management, Tucson, Ariz., pp. 7-12. Lindorff, D. E., and K. Cartwright (1977). Ground water contami- nation: problems and remedial actions, Environ. Geol. Notes II 81, Illinois State Geological Survey, 58 pp. Leopold, L. B. (1974). Water: A Primer, W. H. Freeman, San Fran- CiSCO, Calif., 172 pp. Matthess, G. (1982). The Properties of Ground Water, John Wiley, New York, 406 pp. Miller, D. W. (1981). Basic elements of ground water contamination, in Seminar on the Fundamentals of Ground Water Quality Protec- tion, Geraghty and Miller, Inc., and American Ecology Services, Inc., Cherry Hill, N.J. Miller, D. W., F. A. DeLuca, and T. L. Tessier (1974). Ground water contamination in the northeast states, EPA 660/2-74-056, U.S. EPA, Office of Research and Development, Washington, D.C., 328 pp. Miller, J. C., P. S. Hackenberry, and F. A. DeLuca (1977). Ground water pollution problems in the southeastern United States, EPA 600/3-77-012, U.S. EPA, Office of Research and Development, Washington, D.C., 361 pp. National Research Council (1977). Drinking, Water and Health, Vol. 1, Safe Drinking Water Committee, National Academy of Sciences, Washington, D.C., 939 pp. Nebraska Department of Environmental Control (1980a). Water Qual- ity Report [Pursuant to Section 305(b) of the Clean Water Act], Lincoln, Neb., 303 pp. Nebraska Department of Environmental Control (1980b). Final Report: Nebraska Surface Impoundment Assessment, Lincoln, Neb., 72 pp.

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The Extent of Groundwater Contamination Nebraska Department of Environmental Control (1981). An Investi- ~,ation of the Causes of Nitrate Contamination in the Ground Water of the Lower Big Nemaha Drainage Basin, Lincoln, Neb., 8 pp. New Jersey Department of Environmental Protection (1981). Ground Water Pollution Index, 1975-June 1981, Trenton, N.J., 55 pp. New Mexico Environmental Improvement Division (1980). New Mex- ico Surface Impoundment Assessment, Santa Fe, N. M ., 157 pp. Piskin, R., L. Kissinger, M. Ford, S. Colantino, and J. Lesnak (1980). Inventory and Assessment of Surface Impoundments in Illinois, I1- linois Environmental Protection Agency, Division of Land/Noise Pollution, 160 pp. Pye, V. I., R. Patrick, and J. Quarles (1983). Groundwater Contam- ination in the United States, University of Pennsylvania Press, Phil- adelphia. Robertson, F. N. (1975). Hexavalent chromium in the ground water in Paradise Valley, Arizona, Ground Water 13, 516-527. Rolston, J. L., I. G. Grossman, R. S. Potterton, and E. H. Handman (1979). Places in Connecticut where ground water is known to have deteriorated in quality, U.S. Geol. Surv. Misc. Field Studies Map, MF-981-b. Scalf, M. R., J. W. Keeley, and C. J. LaFevers (1973). Ground water pollution in the south central states, EPA-R2-73-268, U.S. EPA, Washington, D.C., 181 pp. Schmidt, K. D. (1972). Ground water contamination in the Cortaro area, Pima County, Arizona, in Hydrology and Water Resources in Arizona and the Southwest, American Water Resources Association and the Hydrology Section of the Arizona Academy of Sciences, Prescott, Ariz. South Carolina Department of Health and Environmental Control (1980). Inventory of Ground Water Contamination Cases in South Carolina, 58 pp. South Carolina Department of Health and Environmental Control (1981). Inventory of Known Ground Water Contamination Cases and Gen- eralized Delineation of Five Ground Water Recharge Areas in South Carolina, 122 pp. Spalding, R. F., and M. E. Exner (1980). Areal, vertical and temporal differences in ground water chemistry, I. Inorganic constitutents, J. Environ. Qual. 9, 466-479. Spalding, R. F., J. R. Gormley, B. H. Curtiss, and M. E. Exner (1978a). Non-point nitrate contamination of ground water in Merrick County, Nebraska, Ground Water 16, 86-95. Spalding, R. F., G. A. Junk, and J. J. Richards (1978b). Pesticides in ground water beneath irrigated farmland in Nebraska, Pesticides Monitoring J. 14(2), 70-73. Spalding, R. F., M. E. Exner, J. J. Sullivan, and P. A. Lyon (1979). Chemical seepage from a tail water recovery pit to adjacent ground water, J. Environ. Qual. 8, 374-383. Thomas, H. E., and D. A. Phoenix (1976). Summary appraisals of the nation's ground water resources California region, in'U.S. Geol. Surv. Prof. Pap. 813-E. Tucker, R. K. (1981). Groundwater Quality in New Jersey: An Inves- tigation of Toxic Contaminants, New Jersey Department of Envi- 33 ronmental Protection, Office of Cancer and Toxic Substances Re- search. U.S. Congressional Research Service (1980). Resource Losses from Surface Water, Ground Water and Atmospheric Contamination: A Catalog, prepared for U. S. Senate Committee on Environment and Public Works, Washington, D.C., 246 pp. U.S. Environmental Protection Agency (1977). Waste disposal prac- tices and their effects on ground water, Report to Congress, Wash- ington, D.C., 512 pp. U.S. Environmental Protection Agency (1978a). Executive summary: surface impoundments and their effects on ground water in the United States a preliminary survey, EPA-570/9-78-005, U. S. EPA, Washington, D.C., 30 pp. U. S. Environmental Protection Agency (1978b). Surface impound- ments and their effects on ground water quality in the U.S. a preliminary survey, EPA/9-78-004, Washington, D.C., 275 pp. U.S. Environmental Protection Agency (1980a). Ground water pro- tection, U.S. Environmental Protection Agency Water Quality Man- ag,ement Report, Washington, D. C., 36 pp. U.S. Environmental Protection Agency (1980b). Planning Workshops to Develop Recommendations for a Ground Water Protection Strat- egy, Appendixes, Washington, D.C., 171 pp. U.S. Environmental Protection Agency (1981). Computer printout of disease outbreaks attributed to ground water between 1948 and 1980, Cincinnati, Ohio. U.S. General Accounting Office (1978). Waste disposal practices a threat to health and the nation's water supply, CED-78-120, Wash- ington, D.C., 34 pp. U.S. General Accounting Office (1980). Ground water overdrafting must be controlled, a report to Congress of the United States by the Comptroller General, CED-80-96, Washington, D.C., 52 pp. U. S. Water Resources Council (1978a). The Nation's Water Resources, 1975-2000, Second National Water Assessment, Vol. 1: Summary, 86 pp. U. S. Water Resources Council (1978b). The Nation's Water Resources, 1975-2000, Second National Water Assessment, Vol. 2: Water Quan- tity, Quality and Related Land Considerations, 618 pp. U. S. Water Resources Council (1978c). The Nation's Water Resources, 1975-2000, Vol. 3: Analytical Data Survey, 89 pp. University of Nebraska (1980). Maps of ground water nitrate-nitrogen concentrations, reconnaissance sampling of the National Uranium Resource Evaluation program, Nebraska Conservation and Survey Division, Institute of Agriculture and Natural Resources, Lincoln, Neb. van der Leeden, F., L. A. Cerrillo, and D. A. Miller (1975). Ground water problems in the northwestern United States, U.S. Environ- mental Protection Agency, Office of Research and Development, EPA-660/3-75-018, Washington, D. C., 361 pp. Walker, W. H. (1969). Illinois ground water pollution, J. Am. Water Well Assoc. 61(1), 31-40. Weimar, R. A. (1980~. Prevent ground water contamination before it's too late, Water and Wastes Eng. 30-33, 63.

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