EPA 560/3-75-006 THE IMPACT OF INTENSIVE APPLICATION OF PESTICIDES AND FERTILIZERS ON UNDERGROUND WATER RECHARGE AREAS WHICH MAY CONTRIBUTE TO DRINKING WATER SUPPLIES A Preliminary Review Office of Toxic Substances U.S. Environmental Protection Agency Washington, D.C. 20460 January 1976 ------- Document is available to the public through the National Technical Information Service, Springfield, Virginia 22151. ------- EPA 560/3-75-006 THE IMPACT OF INTENSIVE APPLICATION OF PESTICIDES AND FERTILIZERS ON UNDERGROUND WATER RECHARGE AREAS WHICH MAY CONTRIBUTE TO DRINKING WATER SUPPLIES A Preliminary Review Office of Toxic Substances U.S. Environmental Protection Agency Washington, D.C. 20460 January 1976 ------- PREFACE This report is an initial technical review of some of the problems which may be posed by pesticides and fertilizers to drinking water supplies. Prepared for the Office of Toxic Substances by Ecosystems Incor- porated, this final version incorporates some revisions made by the Special Projects Branch of the Office of Toxic Substances under the guidance of David Garrett, Chief of that Branch. This report has been reviewed by the Office of Toxic Substances, EPA, and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Environmental Protection Agency, nor does mention of trade names or commercial products consti- tute endorsement or recommendation for use. ------- TABLE OF CONTENTS SECTION 1 - AN INITIAL ASSESSMENT 1 I. SUMMARY 1 II. GROUNDWATER RECHARGE AND TOXIFICATION FROM AGRICULTURAL SOURCES 3 A. Introduction and Overview 3 B. Types of Contaminants 5 C. Movement of Waste Fluids . 6 D. Control and Removal of Contaminants 7 E. Monitoring Groundwater Quality 8 F. Sources of Information 9 G. Groundwater Assessment 20 III. NITRATES 21 A. Nitrogen Cycle 21 B. Health Effects of Nitrate 26 C. Fertilizers 27 D. Feedlots 30 E. Septic Tank Systems (On Site Domestic Waste Disposal) 38 IV. AGRICULTURAL PESTICIDES 39 A. Introduction and Overview 39 B. Preliminary Correlation Between Organics Found in Drinking Water and Specific Pesticide and Fertilizer Uses 44 C. Laboratory Testing Procedures for Pesticides 50 V. ECONOMIC IMPACT OF GROUNDWATER CONTAMINATION ABATEMENT 52 A. Introduction and Overview 52 B. Cost-Benefit Analysis 52 C. Intangible Benefits 53 D. Economic Impact Analysis 54 ------- E. Primary Costs 55 F. Secondary Costs 55 VI. GROUNDWATER FLOW MODELS 56 A. Introduction and Overview 56 B. Unsaturated Flow 57 C. Saturated Zone 57 D. Dispersion With No Adsorption 59 E. Dispersion With Adsorption 59 F. Summary of Dispersion Models 60 G. Regional Models 60 SECTION 2 - A PROGRAM PLAN FOR MORE DETAILED INVESTIGATION 66 I. INTRODUCTION . 66 II. GENERAL 67 A. Task G-l 67 B. Task G-2 . . 69 C. Task G-3 69 D. Task G-4 . 70 III. NITRATES • . . . 70 A. Fertilizers 70 1. Task FR-1 . 70 2. Task FR-2 - 72 B. Feedlots - 75 1. Task FE-1 75 2. Task FE-2 76 3. Task FE-3 . . 79 C. Septic Systems and Groundwater 80 1. Task S-l 80 IV. PESTICIDES . , 81 A. Task P-l 81 V. ECONOMIC IMPACT OF MEASURES TAKEN TO REMEDY , GROUNDWATER CONTAMINATION 83 A. Introduction and Overview . 83 ii • ------- B. Task E-l: Choose Alternative Remedies 86 C. Task E-2: Determine Primary Industry Effects 87 D. Task E-3: Determine Secondary Effects 89 VI. Modeling 90 A. Task M-l 90 SECTION 3 - BIBLIOGRAPHY 93 111 ------- LIST OF FIGURES FIGURE PAGE l-II-l Groundwater withdrawn, by regions, 1970 in - million gallons a day 10 1-II-2 General Map Showing Annual Runoff and Productive Aquifers in the Conterminous United States 12 1-II-3 Crop Producing Regions 13 1-II-4 Precipitation Map of the Conterminous United States 15 1-II-5 "Precipitation Retained" Map of the Conterminous United States 16 1-II-6 Farm Production Regions 17 1-II-7 Fertilizer-Consuming Regions in the United States 18 l-III-l Major Phases of the Nitrogen Cycle 23 1-III-2 Cattle Feeding Area 36 1-III-3 Feed Cattle Marketed in 23 Major States 37 2-1-1 Activity Streams 68 2-V-l Flow Diagram of Economic Impact Analysis 85 iv ------- LIST OF TABLES TABLE PAGE l-III-l Production of Wastes by Livestock in the United States 31 1-III-2 Population Equivalent of the Fecal Production by Animals, in Terms of Biochemical Oxygen Demand (BOD) 32 1-III-3 Average Daily Manure Production and Compo- sition 33 1-IV-l Organic Compounds Identified in Drinking Water* 45,6,7 l-IV-2 Pesticide Chemicals Identified in Drinking Water Active Ingredients 48 l-IV-3 Non-Active Ingredients of Pesticide Formulations Identified in Drinking Water 49 v ------- THE IMPACT OF INTENSIVE APPLICATION OF PESTICIDES AND FERTILIZERS ON UNDERGROUND WATER RECHARGE AREAS WHICH MAY CONTRIBUTE TO DRINKING WATER SUPPLIES Section 1 An Initial Assessment I. SUMMARY This report presents an Assessment of the impact of intensive application of pesticides and fertilizers on underground water recharge areas which may contribute to drinking water supplies; and also presents a Plan for developing additional information required to define the nature and extent of the impact of agricultural practices on groundwater supplies for public water systems, as required by the Safe Drinking Water Act (PL-93-523). In the perspective of what additional information is needed to determine the time extent of agricultural impacts on underground water recharge, the operation of feedlots represents a significant concern. Special emphasis is therefore placed on this subject. Feedlots, in addition to being a most concentrated source of po- tential pollution, may also offer the greatest range of choices for abatement, some of which might even be economically profitable. Pesticides appear to offer only a marginal threat to groundwater because of their adsorptive properties on soil structure and/or their short-lived persistence. The exception to this statement might be where pesticides are improperly applied, or there exist sandy soils or thin soils overlaying fissured rocks. Groundwater recharge, from streams and lakes polluted with pesticide-contami- nated runoff has not been considered to fall within the scope of the present study even though such runoff originated from agri- cultural areas. Pesticide pollution from "home garden" appli- cations may also represent a genuine problem in terms of use by unqualified persons and improper disposition of residues, con- tainers and excess supplies, but is defined as being outside the scope of the present study. ------- Fertilizers are usually applied at rates designed to yield a maximum agronomic return for the quantities of fertilizers applied, but this is often done on a "rule of thumb" basis. The application rates, methods and associated tillage practices have generally been established without regard to groundwater quality. Surface water runoff considerations have usually been assigned a greater impor- tance. More information is required as to how much nitrate is reaching groundwater because the total annual fertilizers require- ment was applied in one or two heavy treatments, rather than ligh- ter applications made several times during the growing season. Septic tanks on farms present an insignificant source of pollution to groundwater as related to public drinking water supplies. How- ever, the well water supply on that particular farm may be sus- ceptible. Often the design, construction, or maintenance of a septic system or a water well has been inadequate to protect against contamination. On the other hand, cesspools are considered to have a higher pollution potential to groundwater because essentially raw sewage may move directly to the groundwaters. Cesspool installations are now widely prohibited, however, and even though thousands are still in use, it is not deemed necessary to investigate this problem further. There is a need for greater knowledge of the process of nitri- fication and denitrification in various soils and subsoils as a function of soil temperature, climate, and biochemistry. Such studies are needed for both animal waste applications, and for fertilizer and crop cover sources of nitrogen. With regard to possible changes in law dealing with agricultural practices to protect groundwater from toxification it is recognized that impacts on the farmer could be dominant. Not all these effects are ex- pected to be detrimental; in fact, some changes may, in the long run, contribute to increased productivity of the land. Consideration is given to the geologic, edaphic, climatologic, and hydrologic aspects of the problem. In addition, the economic impact of modification of agronomic practices is taken into ac- count. It is to be hoped that the cost of abatement measures may be offset, at least in some instances, by the opportunity for waste recovery as fertilizer or fuel. The findings of the studies on the intrusion of toxic substances into groundwater recharge areas, whether from nitrates or pesti- cides, ought to be modeled to provide predictions of future con- sequences as a result of the continued use of these substances. Modeling will also permit parameters to be varied so as to deter- mine the application levels at which these substances would no longer toxify the groundwater. ------- The Plan for the future work consists of a series of tasks designed to fill the gaps in current knowledge of the degree—and by what mechanisms—groundwater becomes polluted from agricultural prac- tices, and to provide information important for pollution abatement and control. The tasks are grouped under four major headings: (a) Nitrates; (b) Pesticides; (c) Economic Impacts; and (d) Modeling and Simulation. Under the heading of Nitrates, sub-tasks deal with feedlots, fertilizers, septic tanks and problems which relate to several nitrate sources. II. GROUNDWATER RECHARGE AND TOXIFICATION FROM AGRICULTURAL SOURCES A. Introduction and Overview This report has been prepared to help identify program ele- ments required to determine the nature and extent of the impact from agricultural practices on groundwater supplies to public water systems, as stated in the Safe Drinking Water Act (PL-93-523). About 97 percent of the earth's fluid fresh water is ground- water. This groundwater is used as a water supply by about two-thirds of the people in the United States [62]. To pre- serve this most valuable natural resource, a national program of groundwater quality protection and restoration is a neces- sity. A major need in developing such a program is a defini- tion of groundwater pollution problems and potential problems and the scope and significance of each. To determine the extent of these problems the Office of Research and Develop- ment of the U.S. Environmental Protection Agency has initiated a program to assess groundwater pollution problems throughout the United States. Studies have been completed for Arizona, California, Nevada, and Utah [26], the South Central States [62], the Northeastern States [86], and the Northwestern States [95]. The studies for the other regions of the country are at various stages of preparation. These reports will cover the Southeast States (report due March 1976), the Mid- West States (October 1976), East (March 1977), and Hawaii and Alaska (March 1977) [100]. Groundwater is a most important asset in this country in terms of its freshness, usefulness in quality, and in general, quantity. Even though groundwater comprises at least 95 per- cent of the nation's freshwater reserves, only about 20 per- , cent of the total quantity of water now used in the United States is supplied from underground sources [94]. ------- Groundwater collection into aquifers is a direct result of seepage of surface water through percolation, seepage through cracks in underlying rocks and through the natural infilt- ration from lakes and rivers. This same groundwater is brought up to the surface by wells for human, animal, and agricultural consumption, making groundwater and surface water integral parts of a single dynamic system in which the water contin- uously flows between the two levels of the system. The quality of the water changes continuously as a result of this inter- face. Groundwater pollution usually takes place very slowly. This is due to the slow movement of the sub-surface water into the aquifer. It may take many years to pollute groundwater due to its slow movement. However, once groundwater is polluted it may take many many more years, even centuries, and enormous cost, to restore the quality of the water even after the source of the pollution is removed. It is cheaper and easier to prevent pollution in subsurface water than to remove it. There are two basic problems with groundwater contaminations. The first is handling existing cases and the second is to prevent new occurrences. Groundwater pollution arises both from natural phenomena and as the result of careless and deliberate acts of man. Subsurface water pollution can be the result of excessive and uncontrolled fertilization, pesti- cides, industrial and animal wastes, irrigation, disposal of oil field brines and highway deicing salts, accidental spill- age of hazardous and toxic materials, injection of contamina- tion into wells for waste disposal, and other causes. Groundwater quality is an important public concern because of its effect on the health of man and animals and on the growth of vegetation. A lowering of groundwater quality can change the pattern of living in a region because water usefulness has deteriorated. Poor water quality has caused towns to stop expanding and even languish. Feedlots have been obliged to be relocated when the water supply became unfit for animal con- sumption. Man has also contributed to groundwater contamination by dumping urban, industrial, and agricultural wastes, and by polluting surface streams which recharge aquifers. He has created saline conditions in groundwater by means of oil wells and extensive irrigations. Although man's contribution to contamination is large, not all groundwater contamination is the result of man's activities. Some contamination results ------- from minerals leaching from rock formations through which water percolates enroute to an aquifer. B. Types of Contaminants Biological contamination of groundwater may occur when human or animal wastes enter an aquifer. Microorganisms present in the wastes may be carried by the groundwater into nearby water wells and may cause disease when ingested. Inorganic chemical contamination differs from biological contamination in several important ways. Most important are the indestructibility of some inorganic chemicals, the persistence of the pollution created by their presence, and the difficulty in their re- moval. Nitrates in groundwater from agricultural practices, for example, are of increasing concern. The U. S. Public Health Service has specified certain "maximum" concentrations for such substances in drinking water [93]. In arid regions, inorganic chemical contamination is of great concern to agri- cultural water users. Generally, the quality criteria most often applied relate to total salt concentration (total dis- solved solids), chloride, sodium, boron, and bicarbonate. Water low in salts is usually the most desirable for irri- gation, but sometimes only water containing several thousand milligrams per liter of salts is available. High evaporation rates and lack of adequate flushing may cause salt accumu- lation in the root zone with a resulting decrease in crop yields. Reuse and recycling of water for irrigation is a frequent source of salt buildup in both surface and ground- water [32]. Organic chemical contamination is most often caused by such substances as detergents, gasoline, oil, and phenolic com- pounds. Phosphate contained in detergents and chemical fer- tilizers may constitute a hazard if present in excessive concentrations in groundwater. Gasoline and other hydro- carbons often end up as groundwater contaminants because of leaking tanks, pipeline breaks, or spills at the land surface. The presence of minute concentrations of hydrocarbons may result in abandonment of wells because of objectionable odors and tastes. Frequently, chemical additives complicate the contamination pattern. Phenols present in oil refinery or chemical plant wastes are often found in groundwaters. The presence of this contaminant is generally recognized by its taste and odor, which can typically be detected at concent- rations as low as 0.001 mg/1 (the U. S. Public Health Service recommended limit for phenol in drinking water) [42]. ------- C. Movement of Waste Fluids To understand the health and other hazards associated with groundwater contamination, some familiarity with the basic principles of movement of contaminants in a groundwater body is necessary. Groundwater can simply be described as water contained in the saturated pore spaces and fractures of hard rocks and sediments beneath the land surface. It usually does not exist in a static condition but is constantly in motion. ' The rate of groundwater movement is highly variable both vertically and horizontally, and may vary from meters per day to centimeters per day or less. For example, in fractured crystalline rock the movement might be on the order of tens of meters per day, whereas in unconsolidated material it might be a few centimeters per day. The configuration and slope of the water table are important considerations in estimating the directions and rates of travel of wastes in the subsurface environment. Contaminants dumped in an area where the water table is practically level and where little movement of groundwater is occurring will tend to stay in place. However, low gradients can be asso- ciated with high aquifer transmissivities in a given area, and high gradients with low transmissivities are great, the pol- lutant can move rapidly in spite of a relatively flat water table. The thickness and composition of the unsaturated zone over- lying the saturated zone are also important factors. Espe- cially in cases of biological contamination, a thick unsatu- rated zone of fine-grained soil can adsorb and filter much of the pollutants before they can be introduced into the ground- water body itself. Once at the top of the water table, fluid wastes generally will enter the groundwater system with only minor mixing with native groundwater or will float (nitrates for instance) on top of the saturated zone. The contaminant will then move with the groundwater toward its ultimate discharge point, which commonly is a spring or a river. Frequently, however, groundwater flow patterns are modified because of pumping from nearby wells. In such cases, the hydraulic gradient or slope of the water table is toward such a well, and the contaminants converge upon the center of pumping and emerge in the well discharge. In most cases, this is how groundwater pollution is discovered. Under natural conditions and in the absence of pumping, ------- water-table aquifers in the more humid regions discharge groundwater continuously into a nearby surface-water body such as a lake or river. Thus, the groundwater is entering the lake or stream and the aquifer itself cannot be contaminated by wastes carried by the stream. When a well is put into operation in such an aquifer near a stream, however, ground- water levels are lowered and the hydraulic gradient between the well and river may be reversed, causing surface water to flow toward the well. If the stream is polluted, contaminated river water may thereby be induced to flow to the well. According to the laws governing fluid movement in saturated material, the direction of groundwater flow will always be toward points where the total hydraulic head is lowest. In many parts of the Northwest, saline groundwater in deep aqui- fers is under high artesian heads, and it can be induced to move upward into freshwater aquifers where heads are lower. An example would be the situation in which two zones are interconnected through abandoned or improperly sealed wells. D. Control and Removal of Contaminants Because of the generally slow rate of movement of groundwater, a pollutant may exist for years before the problem is dis- covered. Contaminating fluids of different densities do not always move with the main body of groundwater. They can float near the top of the saturated sediments or sink toward the bottom of the aquifer [95]. Thus, determination of the di- rection of flow and areal extent of a contaminated groundwater body can be complex, and can be accomplished only by a rather detailed and costly investigation. i Generally, the most common approach to dealing with contami- nated groundwater is to eliminate the source of pollution as quickly as possible, which is not always feasible. Even if the source of pollution can be removed, the groundwater contami- nation problem still may not be eliminated because a polluted groundwater body normally moves and disperses slowly. The degree of reduction in concentration of contaminants with time is related to such factors as the hydraulic properties of the aquifer and recharge conditions. Nevertheless, long after a source of pollution has been removed, it is not uncommon for the contaminated groundwater body to continue expanding in areal extent for many years and to travel significant dis- tances before its hazardous effects are minimized. Few ------- studies have been conducted to define the degree to which contaminants will attenuate with time and distance from the source. Some recent modeling investigations simulating varia- tion of groundwater quality with time and distance are ex- pected to assist in the prediction of contaminant movement. Other approaches to the solution of groundwater contamination problems are containment or removal of the pollutant. Con- tainment involves limiting the spread of the pollutant within an affected aquifer. Pumping from wells, installation of drains, excavation of affected soils, and artificial recharg- ing are the most common methods used for containment or re- moval . Monitoring Groundwater Quality Another aspect of groundwater contamination is the problem of monitoring chemical and biological quality. Several factors are responsible for this difficulty, including: (a) The complex nature of aquifer systems and groundwater movement. (b) The variety of potential contamination sources. (c) The frequent lack of baseline data. (d) The economics of establishing, a monitoring system. The complexity of hydrdgeplogic conditions was mentioned in previous paragraphs. In most cases it is necessary to define the extent, thickness, direction and rate of movement of the polluted body of groundwater. This requires test wells and often geophysical surveys. The groundwater quality at various depths below the surface must be determined. Chemical tracers may be introduced into the aquifer to study direction and rate of flow of the groundwater. Many wastes are of complex chemi- cal composition, and combinations of different wastes may produce reactions necessitating extensive laboratory work and research to establish the source of pollution. A significant problem in monitoring groundwater quality is the general lack of baseline data. Usually, no thought is given to a monitoring program until such time as a problem is de- tected, often too late to establish a meaningful program. Even where water quality baseline data are available, the information is of limited value because in the past many ------- key constituents were not routinely analyzed [90]. This applies to many of the trace elements such as selenium, molyb- denum, and cadmium, and such other toxic metals as lead and zinc. Finally, the problem of economics influences the establishment of a monitoring program. Federal, state, and often county legislation have pointed to the need for increased surveil- lance of waste discharge movement. Yet, because of limited funds and personnel, a hazard must be quite severe before a polluter, enforcing agency, or water user assumes the economic burden of establishing a monitoring system. Certainly the majority of small municipal water-supply com- panies lack both financing and personnel to establish moni- toring programs routinely. Also, most state agencies do not have adequate financial resources for sufficient trained personnel to enforce effective procedures. F. Sources of Information In determining the quality of groundwater to be used for public drinking water supplies, several sources of information have been used. Hydrologic, geologic, edaphic, climatic, chemical and agricultural data sources were found and uti- lized. Information on the quantities of groundwater were obtained from the U. S. Geological Survey (Murray and Reeves, Circular 676). Here it is revealed that beneath the conterminous United States lie some 65 quadrillion gallons or 200 billion acre-feet of groundwater within a few thousand feet of the land surface, part of which is renewable upon use. About 69 billion gallons a day (77.3 million acre-feet a year) are derived from groundwater reservoirs. This rate, amounting to approximately 20 percent of the total withdrawal use of water in th'e nation excluding hydroelectric use, constitutes only a fraction of the development possible, and the resource is capable of a greatly enlarged role in national water supply [56]. Figure l-II-l shows the magnitude and distribution of ground- water utilization in the United States [94]. Although ground- water is a significant source of water supply throughout the country, predominant usage is in the western part, mainly for irrigation. The nation's systems of groundwater reservoirs vary from ------- Figure 3.-II-1. ' • . •:• Groundwater withdrawn, by regions, 1970 in, million gallons a day 10 ------- reservoirs that are drained and refilled naturally on an annual cycle, to those in which the annual replenishment is but a minor fraction of amounts in storage. Many of the groundwater reservoirs where replenishment is very low in comparison to total volume in storage are in the arid West; significant annual replenishment is more common in the East and other relatively wet areas of the nation. Beyond this general regional classification, conditions of groundwater availability are as varied as the multifarious hydrological settings throughout the country [94]. (See Figure 1-II-2) [85]. About one-third of the nation is underlain by groundwater reservoirs generally capable of yielding at least 50 gallons a minute to a well, and there are large areas where hundreds or even thousands of gallons per minute can be obtained from wells or springs [94]. (See Figure 1-II-2) Generally, if a public water supply is drawn from a groundwater reservoir it will require a well to pump at a rate of at least 50 gallons per minute. Figure 1-II-2 indicates those areas in which our major productive aquifers occur [94, 74]. When a map of agricultural regions is superimposed on this map large areas of the country were eliminated from consideration. Crop producing areas are shown in Figure 1-II-3 [73, 80]. A map of cattle feeding areas is given in the "Feedlots" sec- tion. The remaining areas became the focus for various situa- tions such as fertilizer application [30], pesticide appli- cation [81], and feedlot operation [77]. Alluvial soils in river basins make aquifers there parti- cularly susceptible to high rates of recharge, and thus po- tentially vulnerable to contamination from, for example, feedlot operations [44]. These operations were identified from the U. S. Department of Agriculture Statistical Reporting Service. It was ascertained that feedlot operations have indeed contaminated some groundwaters in some regions, es- pecially along the Platte River [44, 72] and in areas of Iowa and Illinois [88]. In Iowa and Illinois the sand content in the soils contribute to this problem due to their high per- meability. In areas where the high water table is lowered by heavy pumping rates for summer irrigation, but raised again in the winter, there have been problems of high levels of nitrate in the Fall and Winter. This is related to enhanced precipi- tation and in part to the lower demand for nitrates in that season by plants, the decay of vegetation, and the 11 ------- UNtTED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY WATER-SUPPLY PAPER ISOO PLATE I Pattern* detiiM*tc BTCM underlain by o«e or nor* muiltn capable of rieldioc to l *dU *t lent M ffaa of wttcr ± «nifcn intertwhkd with or ovcrtain by ODCWMbdMcd or »«jJeoo- i »juihn Coatonnof «aDwlnmoff.»iaA«» GENERALIZED MAP SHOWING ANNUAL RUNOFF AND PRODUCTIVE AQUIFERS IN THE CONTERMINOUS UNITED STATES SCALE MO 000 01 Figure 1-II-2 ------- Notes: 1. Ref.: C.R. Taylor and E.R. Swanson, The Economic Impact of Selected Nitrogen Restorations on Agriculture and 20 Other Regions in the United States, University of Illinois at Urbana - Champaign March, 1975. 2. List of areas corresponding to region number as available from the authors. 3. Crop production in the shaded areas is minimal. Figure 1-II-3 Crop Producing Regions ------- decrease in tillage practices [1]. Figure 1-II-2 includes the surface runoff of water from the land. Relating this with the pattern of precipitation (Figure 1-II-5); an estimate of aquifer recharge potential is deve- loped (Figure 1-II-4). It.should be recognized that the soil retention level of the precipitation is not so high as would appear from Figure 1-II-5 [94]. Evapotranspiration accounts for much loss of water from the soil. In the arid regions west of the Mississippi River, there is often less than an inch of recharge whereas Figure 1-II-4 suggests several inches in most arid regions [54]. The Agricultural Research Service of USDA has investigated this rate for many soils and crops in connection with practices and climatic conditions. State and county extension services in many regions have developed data of this type also. The evapotranspiration rates are highly variable depending on a multitude of parameters [70]. Data is presented in various forms and formats. The farm producing regions are presented by the U. S. Department of Agriculture as shown in Figure 1-II-6 [81]. The U. S. Bureau of Census lists fertilizer consumption with the regions divi- ded as shown in Figure 1-II-7 [37]. There are several sources of data on fertilizer consumption. The U. S. Department of Agriculture publishes Agricultural Statistics and also Commercial Fertilizers, Consumption in the United States [78]. The U. S. Bureau of Census publishes Agricultural Statistics also [79]. The National Fertilizer Development Center of the Tennessee Valley Authority published the 1974 Fertilizer Summary Data (ed. Normal L. Hargett) [30], which gives an extensive breakdown of fertilizer usage by crop, state and composition. These data can be further de- fined by contacting individual state and local extension service units. The University of Maryland's Bureau of Busi- ness and Economic Research has projected consumption of fer- tilizers throughout the United States for the years 1971 through 1985. In 1974 there were approximately 175 million fertilized acres [37]. Feedlot statistics have been obtained through the U. S. De- partment of Agriculture, the EPA, and the Bureau of Census [77]. The University of Maryland's Bureau of Business and Economic Research has made predictions of growth rates of feedlot beef production through 1983 [37]. Further feedlot information is included in the "Feedlots" section of "Nit- rates". 14 ------- UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1800 PLATE 2 Ln for Select on National Water SUeourcee of the United Statee Senata by Usa United Statee Department of Agriculture. 1959. Prepared fram feohyetal atop by U. 8. Department of Commerce, Weather Bureau data ba**d OB JO year normal*, 19Zl-19SOof 2T4 etattona, •oppl.m.nled by Isohyetal line prtdpiuriofi, in irtchua. irrtgultr Boundary of water-resource region Se« also plate 4 PRECIPITATION MAP OF THE CONTERMINOUS UNITED STATES 300 0 . 3QO 6OO 9OO KILOMETERS Figure 1-II-4 ------- UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL' SURVEY . SUPPLY PAPER 1800 PLATE 3 prepared for Select Vatar Resourcee of the Unit** &(•«*• Stn&te by tb* United Stttoe D«n*rtii>ent at "Precipitation retained" line s prtcipitotion mmul runoff, incnts; mttrvtl PRECIPITATION RETAINED MAP OF THE CONTERMINOUS UNITED STATES 300 0 3OO 6OO 9OO KlLOMCTERS Figure 1-II-5 ------- U.S. DEPARTMENT OF AGRICULTURE NEC. ERS 1399-42 (8) ECONOMIC RESEARCH SERVICE Figure 1-II-6 Farm Production Regions 17 ------- SOURCE: U.S. Bu.eou of Cenjui, 1964 Figure 1-II-7 Fertilizer-Consuming Regions in the United States 18 ------- The distribution of soils [51] and geology throughout the United States has been compiled and mapped by the Soil Con- servation Service (USGS sheet number 86, titled "Soils" [91] and USGS sheet number 74, titled "Geology") [92]. Thes'e map- pings are not included in this report because of their size and detail and multicoloring. The soils map and the accom- panying soils descriptions is very useful in conjunction with other maps to focus our attention on areas where problems of agricultural impact on groundwater are most likely to occur. The USDA has also an ongoing program for defining soil pro- perties throughout the United States. State and local agri- cultural extension services have files on details of soils and some geology within their jurisdiction. Land grant colleges in each state have received Federal funds over the years and have studied local soils extensively. However, there is still a need to better characterize the relationships of soil, crop, and nitrate-N reactions in many areas. The groundwater quality data, while still relatively limited, is available from several sources. It has come from the Soil Conservation Service, the U. S. Geological Survey, from state geological surveys (often the state programs are cooperative arrangements with the USGS), and EPA reports. Further soil, hydrology, and water quality information is available through the files of the Water Resources Departments and the Water Resources Research Centers of each state. The latter source is the more valuable source of information because of its research nature. The major problem involves access to the data. Although the data is available, it is not formally published, but exists in reports in files in the various centers and departments. Fortunately the centers do publish a list of the reports on a biweekly basis. A note of interest is that each Water Resources Research Center is given a grant of $100,000 a year by the Department of Interior [101]. It is anticipated that cooperation with these centers will be invaluable in identifying problems. Data on water table depths and aquifer profiles are compiled from well digger reports. It should be noted that the mixing of agricultural pollutants in an aquifer is minimal because of the predominance of lami- nal flow in these bodies [95]. The nitrates and pesticides that do enter an aquifer through percolation tend to "float" in the upper level of the aquifer. When using well data to determine the degree of contamination in an aquifer it is important to know the depth in the aquifer at which the sample was taken. It is also important to know whether the draw down of the aquifer has been sufficient to bring waters from the 19 ------- upper layer into the pumped region. The condition of the well casing can affect the water drawn. If the casing is permeable the well is very susceptible to seepage of nitrates and fertilizers into the aquifer. Data taken during the Fall and Winter months will tend to show higher nitrate concentrations [2]. Data should therefore be identified as to the season in which it was taken. Climatological data is obtained primarily from the National Weather Service of the National Oceanographic and Atmospheric Administration (NOAA). The data on surface runoff, evapo- transpiration, and percolation through the ground are the realm of the USGS, Soil Conservation Service, the Corps of Engineers and to a lesser degree, the US.DA. G. Groundwater Assessment Generally, groundwater quality in the United States has not yet suffered severe degradation from agriculture. Locally, aquifers have been degraded due to operations of feedlots without proper controls 6r in connection with excessive and poorly timed fertilizer applications and.other popr agri- cultural practices, including, in a few reported instances, careless pesticide applications. The objective is to prevent further deterioration .of aquifers from"which public drinking supplies are drawn. The second problem is to determine what future deterioration is to" be anticipated with respect to various agricultural practices, with projected changes in operational parameters incorporated. This will require the use of mathematical modeling and computer simulation. It is believed that as farmers .become more scientific, and even more economical in their practices, the polluting impact of their operations will be reduced significantly.. Two major points need to be considered: (a) more information is re- quired on plant demand for nutrients and the proper rotation of crops to minimize nitrate percolation through soils [67]; (b) farmers must make better .use of extension services and other good agricultural sources to determine the characte- ristics of their, soils, even to. the extent of fertilizing and planting their farms at different times and rates [102]. Feedlot waste handling and. disposal needs further assessment [65.]. New containment, and .application practices are now 20 ------- available and sometimes in use. A broad program of assessing the effectiveness of these techniques in preventing ground- water (and surface water, too) contamination is essential. This will require monitoring of various feedlot sites and the adjoining fields for a set of interesting locales (in terms of soil type, climate, animal population, etc.). III. NITRATES A. Nitrogen Cycle High nitrate concentrations in drinking water are a potential health hazard and should be of concern to the user. They not only render the water unsafe for use in infant feeding, but generally indicate that the supply is contaminated [50]. The element nitrogen is a gas composing about 79 percent of the earth's atmosphere. It is relatively inert to chemical reaction and ordinarily does not occur abundantly in rocks or water, either in elemental form or in compounds. However, nitrogen and nitrogen compounds, which are essential to plant life and growth, do occur abundantly in soils and subsoils. Their presence there is due largely to bacterial action. Certain bacteria remove nitrogen from the air and fix it in plants and soils in the form of ammonia and more complex compounds, whereas other bacteria change nitrogen compounds from one form to another. Other sources of nitrogen compounds in the soil are nitrogen-fixing legumes, decomposing plant and animal tissues, animal and human wastes, nitrogen fertilizers, and surprisingly, lightning [19]. Because urea, a nitrogen compound in the waste of all animals, is readily converted to nitrate by bacterial action, barnyard and feedlot wastes are locally important contributors of nitrogen compounds to the soil. Septic tanks, cesspools, privies and sewage outlets to the soil, together with silo seepage, also are local sources of contamination. Ways in which nitrogen compounds accumulate in the soil and are changed from one to another are referred to as the nitrogen cycle. There are three major forms of nitrogen in mineral soils: (a) organic nitrogen compounds associated with the soil humus, (b) ammonium nitrogen adsorbed by certain clay minerals, and (c) soluble inorganic ammonium and nitrogen compounds [50]. 21 ------- Most of the nitrogen in soils is associated with the organic matter. In this form it is protected from rapid microbial release, only 2-3 percent a year being mineralized under normal conditions [50]. About half the organic nitrogen is known to be in the form of amino compounds. The form of the remainder is uncertain. Some of the clay minerals have the ability to fix ammonium nitrogen between their crystal units. The amount fixed varies depending on the nature and amount of clay present. Up to 8 percent of the total nitrogen in surface soils and 40 percent of that in subsoils has been found to be in the "clay-fixed" form [50]. In most cases, however, both these figures would be considerably lower. Even so, the nitrogen so fixed is only slowly available to plants and microorganisms. In all soils there is considerable intake and release loss of nitrogen in the course of a year accompanied by many complex transformations. Some of these changes may be partially controlled by man while others are beyond his command. This interlocking succession of largely biochemical reactions constitutes the nitrogen cycle (See Figure l-III-l) [4]. It has attracted scientific study for years, and its practical significance is beyond question. The nitrogen income of arable soils is derived from such materials as commercial fertilizers, crop residues, green and farm manures, and ammonium and nitrate salts brought down by precipitation. In addition, there is the fixation of at- mospheric nitrogen accomplished by certain microorganisms. The depletion is due to crop removal, drainage, erosion, and to loss in a gaseous form. Much of the nitrogen added to the soil undergoes many complex transformations before it is removed. Proteins are converted into various decomposition products, and finally some of the nitrogen appears in the nitrate form. There are nitrifi- cation, mineralization, and denitrification processes which take place. Mineralization (or ammonification) is the breakdown of organic nitrogen to ammonium. Nitrification is the oxidation of this ammonium, or ammonium from fertilizers, to nitrate. Factors affecting this process are soil characteristics, water con- tent, aeration, and temperature. The rate of nitrification tends to decrease sharply when the oxygen content of soil falls below 2 percent or when soil air space is nearly saturated 22 ------- ANIMALS N-FIXATION >r FERTILIZER and RAIN LOSSES GASEOUS LOSS RESIDUES, MANURES and WASTES SOIL ORGANIC MATTER l\ -NH/ Figure l-III-l Major Phases of the Nitrogen Cycle 23 ------- with water. The maximum rate of nitrification occurs in soil temperatures of about 30° C. and is very slow at 7° C. Nitrate can be used by plants, denitrified, leached to ground- water, or remain in the soil and be available for subsequent crops. Denitrification is the microbial reduction of nitrate to harmless nitrogen gas [4]. It is an important factor in determining the amount of nitrate available for leaching to groundwater. Denitrification generally takes place in soils when anaerobic conditions prevail and an energy source such as decaying organic matter is present. Organic nitrogen and ammonium forms must be oxidized to nitrate before denitri- fication takes place. Under favorable conditions, a substantial amount of denitri- fication occurs in or near submerged tile drains. This de- creases the amount of nitrates present in the tile drain effluent. Denitrification also removes nitrate from the root zones of crops, such as rice, that are submerged in water for extended periods of time. Temperature affects the mineralization or ammonification of nitrogen, which influences the nutrient content of runoff and leached waters. During cold periods, plant activity is re- tarded, thereby reducing the rate of nutrient utilization and water consumption. Variability in temperature is also im- portant. If frozen land is thawed at the surface by rainfall, leaving a frozen sublayer that prevents percolation of water, surface runoff and erosion occur. Freezing of plant material tends to rupture plant cells, and nutrients are then subject to leaching during spring thaw. The nutrient content, permeability, and structure of agri- cultural soils are important factors that may have a bearing on the nitrate in ground and surface water. The nutrient accumulation in the soil and substrata is a function of basic soil properites, geologic deposits, decomposition of organic matter and peat, presence of nitrogen-fixing plants, soil organisms, animal and human wastes, and inorganic sources such as fertilizer and precipitation. The energy associated with the impact of falling raindrops affects the amount of sediment in runoff and the rate of water infiltration. Adequate ground cover will absorb the raindrop impact and protect the surface cover. Forests and grasslands generally have higher rates of water infiltration than plan- tings of agricultural row crops when soil and slope conditions are otherwise equal. 24 ------- Permeability and water retention characteristics of soil affect the amount of water passing through the root zone. If nitrate is present, it will move with the water and may even- tually enter the groundwater. The concentration of nitrate in the groundwater depends on the amount of nitrate leached, the volume of water passing through the soil profile, and the transit time of the leachate from root zone to water table. Transit time is related to the hydraulic conductivity of the soil profile, depth of the water table, and degree of soil saturation. In some areas it may take 20-30 years for the leachate to pass from the root zone to the water table. A sandy soil will not retain as much water in the root zone as a loam soil, and so has a higher leaching hazard. Therefore, less nitrogen is utilized by plants and more nitrogen is leached below the root zone in sandy than in less permeable soils. Geologic materials underlying soils may restrict the downward movement of water. Under such circumstances, nitrogen will not contaminate deep aquifers, but may accumulate in perched water tables. Ordinarily, most of the nitrate in groundwater has been leach- ed from the soil by infiltrating precipitation. Thus, where nitrate is especially abundant in the soil, the groundwater generally is high in nitrate. Very high concentrations in well water often are due to contaminants reaching the water table at or near the well site. For example, a poorly fitting well cover permits contaminants to enter the well directly, and open space or highly porous material surrounding the well casing permits contaminants to infiltrate rapidly to depths where they can enter the well through holes in the casing or through the screen. Shallow dug wells, particularly those walled with wood, stone, brick, or jointed tile, are the most likely to yield high-nitrate water owing to introduction of contaminants at or near the well site. Generally, high nitrate concentrations in water from deeper drilled wells are due to leaching of nearby tracts of nitrate-enriched soil and sub- soil. Drinking water standards have been set by the U. S. Public Health Service (1962) at a safety limit of 45 ppm nitration, or 10 ppm nitrate as nitrogen, as a safeguard for people using municipal water supplies. Although no limit has been set specifically for rural domestic supplies, the potential dan- gers of nitration concentrations greater than 45 ppm should be recognized. 25 ------- B. Health Effects of Nitrate The best known problem due to nitrate consumption is methe- moglobinemia, a cyanosis which is brought about by reduction of nitrate (NC>3) to nitrite (N02) by bacteria in the digestive tract, followed by absorption of the nitrite into the blood- stream where the nitrite oxidizes the ferrous ion (Fe ) *n hemoglobin to ferric ion (Pe*44"), thereby preventing the transport of oxygen by the hemoglobin. This results in a gradual suffocation (cyanosis). Infants are most susceptible since the acidity of their stomachs is considerably less than that of adults, resulting in a more favorable environment for the nitrate-reducing bacteria. The digestive system of animals such as cattle (ruminants) also is conducive to this bacterial action. Therefore, when a nitrate problem occurs, it is first reflected in health problems of cattle or human infants [50]. Methemoglobinemia is not well understood. The nitrate or nitrite concentration at which methemoglobinemia becomes a problem may vary widely, and is most likely influenced by some as yet unidentified factor or factors. Because of the methe- moglobinemia problem, the U. S. Public Health Service has set a recommended maximum limit of 45 ppm nitration for potable water. However, water containing over 1000 ppm nitrate has been found with no apparent ill effects to the local popu- lation. In other areas, methemoglobinemia has resulted from using water with as little as 50 ppm nitration [9]. Clearly, more work is needed in the whole area of methemglobinemia. One point deserves further clarification. The high suscepti- bility of animals and human infants to methemoglobinemia derives from the bacteria in their digestive systems which can convert nitrate to nitrite. If the water which is being consumed already contains nitrite, however, even healthy adults will be susceptible. The presence of nitrite in drink- ing water results from at least two known causes. First, if the contamination is from surface pollution (e.g., barnyards or septic tanks) nitrite can be present due to incomplete oxidation of the nitrogenous waste materials. Second, nitrate in the groundwater can be reduced to nitrite by a chemical reaction with iron pipe or zinc coated (galvanized) pipe. This reaction consists of corrosion of the metal, with the nitrate acting as a hydrogen depolarizer. Water contaminated with nitrate cannot be purified by boiling. The nitrate concentration will instead be increased due to the loss of water by evaporation. 26 ------- There is increasing evidence that nitrate and especially nitrite may be linked to cancer. It was shown by Lijinsky and Epstein [43] that nitrite can react, under the conditions of temperature and acidity in the human stomach, with secondary amines (from cooked foods) to form nitrosamines, some types of which are highly carcinogenic. Other studies also indicate a relationship between nitrate and cancer. If such a relation- ship is proven, the Public Health Service limit of 45 ppm for nitration in drinking water will have to be reevaluated. In addition, it may be even more important to set limits on nitrite in drinking water. Clearly not all the effects of nitrate are yet known; but it is believed that livestock may develop thyroid problems, rickets, enteritis, arthritis, and generally poor health from ingesting nitrates. C. Fertilizers Fertilizer Nitrogen. Fertilizers are one of the major agri- cultural sources of potential pollution of the groundwater. The three major elements in fertilizers are nitrogen (N), phosphorous (P) and potassium (K). Nitrogen is the main pollutant in the form of nitrates. During 1973, 43 million tons of fertilizer material were applied throughout the United States, of which 8.3 million, 5.1 million, and 4.6 million tons were nitrogen, phosphorous, and potassium, respectively [30]. • . i To meet the increasing demand for food by an expanding popu- lation, oxidized soluble forms of nitrogen have been intro- duced through new technology to supplement the slow process of nitrification and symbiotic N fixation. This effort has resulted in greater use of commercial nitrogen, often in addition to heavy application of manure. All nitrates are water soluble and have the potential to move into the ground- water and thereby create a potential health hazard. The atmosphere is usually considered to contribute from 2 to 6 pounds of nitrogen to an acre of land per year (Allison [3], Eliassen, et al [18], Hutchinson, et al [34]). Several studies have been conducted on the occurrence of nitrite and nitrate in water supply systems (Smith [66], Doneen [15]; McHarg; Erwin, et al [20]; Murphy et al [49]). Very little is known of the extent of fluctuation in nitrate concentration in water wells. Contaminating sources have seldom been pinpointed. Environmental variables, well depth, well location, precipitation and agricultural practices con- tribute to the above fluctuations. 27 ------- Nitrate derived from biological fixation of atmospheric nitrogen and nitrification are discussed in the following reports: Starky [71]; Hirsch [33]; Marshall, et al [46]; Brezonik [7]; McCoy [47]; Thompson [75], and other reports. Nitrate from naturally occurring deposits were discussed by Mansfield, et al [45], and Ingols, et al [35]. The intrusion of inorganic nitrogen originating from farmland as a potential source of nitrate-nitrogen in both surface and groundwater supply is discussed in the following papers: Corey, et al [11], Stewart, et al [72], Commoner [10], Krause, et al [40], Harmeson, et al [31], Welch and Kohl, et al [39]. The concentration of nitrate in groundwater is generally highest following wet periods and lowest during dry periods. Seasonal variations may be further enhanced by other factors such as geologic structures i.e.: characteristics and depth of soil, subsoil and bedrock formation, degree of and inter- connecting crevices in rock formation, presence of a recharge- able aquifer and amount of recharge water, as well as amounts of nitrogen applied. Olson reported that the maximum downward migration rate of N03 in silt loam soil is in the range of 1 to 1-1/2 feet per year. The rates for sandy soil will be much higher while those for clay soils will be lower. Shallow wells (less than 50 feet in depth) are more apt to show large and frequent increases or decreases of nitrate concentration. Deeper wells tend to show less intensity of nitrate fluctuations. Efforts to obtain higher yields per unit of land through fertilization, whether the fertilizer is organic or inorganic, nearly always create greater potential for nitrate to be carried into waterways. When the efficiency of nitrogen use becomes low, greater losses of nitrogen occur, particularly in well drained soils, and the nitrogen may then escape to leach- ing waters. Low cost fertilizers tend to encourage ineffi- cient and excessive usage of nitrogen fertilizer on the farm. Because intensification of agriculture favors greater decom- position of native soil nitrogen, the nitrate content of underground waters may rise. However, in oxygen-deficient soils with high water tables, the nitrate may be converted to nitrogen gas. In humid regions, the nitrate concentration in water perco- lating through cultivated soils is a function of the fertility 28 ------- level of the soils. The amounts of water percolating through the soil at any given time, the degree of nitrate removal by crops, and the activity of denitrifying microorganisms deter- mine the nitrate concentration in soil leachates. Industrial nitrogen fertilizers may cause some temporary changes in the biological processes essential for soil fer- tility, but the changes are neither permanent nor irrever- sible. The benefits of fertilizer use, associated with the increased availability of an element essential for plant growth, far outweigh the temporary inhibition of certain soil microorganisms. Reducing nutrient losses to groundwater from agricultural nonpoint sources can be accomplished with two general app- roaches: (a) determining and applying appropriate amounts of plant nutrients at the proper time and in the proper place, and (b) adopting improved cultural practices, including con- servation tillage and crop rotations, that minimize nutrient losses. Control measures should be selected in light of their economic and technical feasibility, as well as their effect in reducing nutrient losses. Phosphorous in Fertilizers. When fertilizer phosphate is added to the soil it is rapidly incorporated into relatively insoluble compounds. Because of the insolubility of these compounds, leaching losses are minimal and so groundwater contamination from fertilizer phosphorous is not a problem. Phosphate compounds are generally non-toxic, but tend to cause eutrophication of surface waters. Potassium in Fertilizers. The third macronutrient commonly added to soils is potassium. Little is known about its function in plants. Drainage waters from soils to which potassium has been added have been shown to contain considerable quantities of potassium. In other instances, more than 90 percent of the added potassium has been recovered by crop removal. Leaching of potassium depends on the mineral composition, the amount of soluble organic matter, and the base exchange capa- city of the soil. Potassium has not been found to be harmful to humans or live- stock. On the contrary, potassium is known to be essential to muscle tissues in animals. Some people have been found to have a potassium deficiency. Though potassium may enter a groundwater supply, its effects have not been found to be harmful. 29 ------- D. Feedlots Animal Wastes/General. Livestock and poultry production in the U. S. is becoming concentrated in large scale, confinement type operations. These include multi-hundred - cow dairy operations, multi-thousand - head beef and hog feedlots and enterprises with many thousands of birds. Such large con- centration of animals and birds have greatly magnified the problem of handling the animal wastes. Production of wastes by livestock is summarized in Table l-III-l [98]. , Population equivalent by various kinds of livestock is given in Table 1- III-2 [98]. For example, a feedlot of 10,000 head of cattle has about the same waste disposal problem as a city of 164,000 people. Such a city will use approximately 8.2 mgd to carry off the sewage [98]. Such quantities of water are never used and seldom available at feedlots. The composition of some animal wastes are given in Table 1-III-3 [57]. The primary problem in handling animal wastes involves coping with the high BOD. Untreated municipal sewage has a BOD of about 100 to 400 ppm. Wastes carried in runoff from barnyards and feedlots may vary in BOD from 100 to 10,000. Many in- stallations use lagoons for oxidation but success has not been complete. Such wastes, when deposited on the soil, can lead to higher nitrate concentration as well as higher salt loads in the adjacent waters, surface and underground. Heterotrophic Nitrification. The nitrate in soil and ground- water may originate from microbial transformation of manure returned into the soil. Traditionally, nitrification was considered the work of autotrophus in which ammonium is oxi- dized to nitrite and subsequently, to nitrate. Heterotrophic nitrifiers have been reported as potential nitrate by Hirsch, et al [33], and Marshall, et al [45]. Thus, the compounds important for nitrification are no longer limited to inorganic nitrogen but include a series of amino acids (peptides) which may be converted to nitrates. Thompson (1969) concluded that it is reasonable to assume that nitrate pollution of ground- water may be attributed to heterotrophic nitrifiers where large amounts of wastes are returned to the soil. Denitrifying Organisms. Present day farming practices often lead to situations in which nitrates accumulate faster, by nitrification due to heavy application of commercial ferti- lizers, than they are removed by either crops or denitrifi- cation. Crabtree (1972) reported that the total number of 30 ------- TABLE l-III-l Production of wastes by livestock in the United States. [98] u> Livestock Cattle Horses [1] Hogs Sheep Chickens Turkeys Ducks rn _ +. _ 1 lotaj. U.S. population 1965 Millions 107 3 53 26 375 104 11 Solid wastes [1] G. /cap. /day 23,600 16,100 2,700 1,130 182 448 336 Total production of solid waste Million tons/yr. 1,004.0 17.5 57.3 11.8 27.4 19.0 1.6 11 IB f. , X JO . O Liquid wastes G./cap. /day 9,000 3,600 1,600 680 Total production of liquid wastes Million tons/yr. 390.0 4.4 33.9 7.1 A i R A H JJ . t [1] Geldreich and others. [2] Horses and mules on farms as work stock. ------- TABLE 1-III-2 Population equivalent of the fecal production by animals, in terms of biochemical oxygen demand (BOD). [98] Biotype Man Horse Cow Sheep Hog Hen Fecal (G. /cap. /day) 150 16,100 23,600 1,130 2,700 182 Relative BOD/ unit of waste (lb.) 1.0 0.105 0.105 0.325 0.105 0.115 Population equivalent 1.0 11.3 16.4 2.45 1.90 .14 32 ------- TABLE 1-III-3 Average Daily Manure Production and Composition [57] ITEM Wet Manure Total Solids Volatile Solids Nitrogen P2^5 K20 HOGS 7.000 1.120 0.950 0.050 0.030 0.048 (After Proctor, 1964) CHICKENS (lb/d) 0.2500 0.0720 0.0550 0.0040 0.0031 0.0014 CATTLE (lb/d) 64.00 10.20 8.20 0.38 0.11 0.31 33 ------- denitrifiers increased as the rate of manure application in- creased. Denitrifying bacteria were found regardless of aerated or water logged soils, with or without tho presence of detectable nitrites or nitrates. Denitrification and nitrate reduction by heterotrophics may occur only when a sufficient amount of nitrite or nitrate is present in a given microbial environment lacking in other more suitable hydrogen acceptor. A question inevitably raised is why the accumulation of such high nitrate content in the groundwater supply exists in the presence of large number of nitrifiers. A reasonable ex- planation is that the denitrifying bacteria formed may not be active in the denitrification process because the soils are sufficiently aerobic or lacking in hydrogen donor compounds; aerobic conditions inhibit the denitrification process re- gardless of the presence of nitrates. Feedlot Operations. Presently, the large, mechanized com- mercial feedlot accounts for many of the livestock fed for slaughter. . In the past, animals were fed in small units, and wastes were considered an asset. Today, the concentration of many animals in one unit creates enormous waste-management problems. A cattle feedlot of 50,000 capacity covers ap- proximately 200 acres and produces approximately 450,000 tons of wet manure and urine annually. This manure contains about 15,000 tons of dry mineral matter, 60,000 tons of dry organic matter, and 2,800 tons of nitrogen. Pollution of groundwater can occur directly beneath the pens, beneath basins used to impound runoff, and beneath cropland treated with wastes or runoff from the feedlots. Increased nitrate concentrations found in Missouri water supplies have been attributed to feedlots and not to ferti- lizer use on farms. In a Colorado study [72] profile, samples were obtained from the surface to bedrock or to the water table. Nitrate content of the profiles was influenced by land use. Nitrate content in 20 feet of profile under cattle feedlots was as high as 5,000 Ib per acre, the average for 47 feedlots being 1,436 Ib. For other kinds of land use the average values were: virgin grassland, 90 Ib.; unfertilized wheat-fallow land, 261 Ib.; and irrigated land not in alfalfa, 506 Ib. Nitrate gradients in the profile showed accumulations at the soil surface, with concentrations decreasing with depth. Nitrate content in the water at the water table sur- face, and at the 20 ft. depth in the soil showed little dif- ference for each land-use [72], The question is what happened to the nitrate? There was evidence that water was moving 34 ------- through the profile and that some nitrate was moving with it. The decrease in nitrate with depth was attributed to denit- rification, the process whereby microorganisms reduce nitrate to nitrogen gas. The greatest decrease in nitrate concent- ration occurred under feedlots where an abundant supply of carbonaceous material was present in the soil water to serve as an energy source for the microorganisms. Denitrification, therefore, appears to be significant in determining the fate of nitrate moving through soil profiles, particularly those under barnyards and feedlots. Even if nitrate concentrations remain low, other pollutants can degrade the quality of groundwater. The Colorado study revealed that several wells were abandoned near feedlots, even for livestock use, because of poor water quality. The largest differences between water samples collected under feedlots and adjacent irrigated fields were in the concentration of ammo- nium and organic carbon, a measure of soluble organic matter [72]. The literature has shown that feedlots can have a notable impact on the quality of groundwater. Feedlot design factors which may affect groundwater should be investigated and manage- ment techniques re-evaluated. Cattle-Feeding Areas. Not long ago cattle feeding was almost synonymous with Corn Belt feeding. There the surplus grains were available for feeder cattle brought from the range areas. Since then cattle feeding has begun to develop in other re- gions also. Areas in California, Arizona, the Plains States, and Colorado represent some of the newer centers of concent- ration of cattle feeding. (Figure 1-III-2) [77]. Cattle feeding is a major activity in those areas where the combination of feed supplies, feeder cattle, markets, and other resources are favorably balanced. In each region, however, there are specific locations in which feeding oper- ations are concentrated. Some of these locations cover broad geographic areas, as in the northern portion of the Corn Belt while in other regions, the industry is confined to small areas. The fed cattle marketed in 23 major states is given in Figure 1-III-3 [65], Nearly all parts of the country now have some cattle feeding, Such regions as the Southeastern and mountain States account for hardly more than 2 or 3 percent of the number of cattle fed nationally, but each region has several areas of concen- tration. These areas are small, but their level of output 35 ------- Colllt Ittding arioi nprtsont location but not Kolumt of tollli lit. U.S. DEPAtTMENT OF AGIICUITUIE NEC. EIS 7*91-70 (5) ECONOMIC IESEAICH SERVICE Figure 1-III-2 Cattle Feeding Area 36 ------- CO Figure 1-III-3 Feed Cattle Marketed in 23 Major States ------- is sufficient to make feeding of significance to the agri- cultural economy of the local areas. E. Septic Tank Systems (On Site Domestic Waste Disposal) The three most commonly used systems for on site domestic waste disposal are the septic tank and its associated sub- surface distribution system, the cesspool and the privy. The septic tank system is the most acceptable and sophisticated of the on site domestic disposal methods, and is installed at new housing sites when local ordinances permit and when public sewer service is unavailable. The cesspool, which is no longer generally approved, is usually an underground sump filled with stones and is intended to settle out larger solids discharged from domestic plumbing. These systems work well only in very coarse or highly fissured materials, but in essence discharge raw sewage which moves easily to ground- water. The privy is usually designed as an open pit privy or closed vault privy. These are usually located where pres- surized water is not available. Because the open pit gene- rally receives only human wastes and paper the potential for groundwater pollution is small. Closed vault privies retain all wastes and must be pumped out periodically, and so are not usually a groundwater problem. Problems often associated with privies are odor, disease-carrying insects, and maintenance. About twenty million individual housing units, representing about 29% of the United States, discharge their domestic wastes through individual on-site disposal units. These are primarily (85%) septic tanks and cesspools. Of this number cesspools account for about two hundred thousand units [89]. The principal factors and variables which determine the mag- nitude of the problems from septic systems as would be found on farms are the geology, the depth to the water table, the precipitation, and the location and design of the system with respect to other facilities [42]. Individual problems of well contamination can occur anywhere in the country, but when the problem is the result of con- tamination from the septic system it can usually be corrected by the redesign or relocation of the well or septic system. Very often the well has been poorly cased or located, in which event nitrate and coliform contamination can be expected [89]. Areas in which there are less than 10 septic systems per square mile do not present a threat to public drinking water supplies which draw from groundwater, except where the septic 38 ------- system is located too close to the well and causes direct contamination [89]. It is hard to differentiate the effects of nitrate pollution of groundwater by a septic system from those of a barnyard or feedlot, if these sources are within close proximity of each other. Data on the density of septic systems has been obtained through the 1970 Census of Housing [83]. The control of septic systems is generally through local, county, or state agencies. The records of well contaminations and septic tank failures are kept in the files of these agencies. The in- dividual Water Resources Research Centers also have collected data within their jurisdictions. Most state Environmental Health Departments will test water samples for nitrates free of charge. Within the EPA the Office of Air and Waste Management has a Solid Waste Management Program that includes the assessment of problems created by septic tank systems. They are presently engaged in determining the dimensions of this problem [89]. EPA's R. S. Kerr Environmental Research Laboratory at Ada, Oklahoma, has recently initiated a long term septic system study. IV. AGRICULTURAL PESTICIDES A. Introduction and Overview In 1964, 693 million pounds of agricultural pesticides - insecticides, fungicides and herbicides - were applied to some 83 million acres of land [98]. When these chemicals are applied directly to the environment, it is obviously impossi- ble to avoid exposing most, if not all, of the organisms in our environment to the insecticides. In addition, these chemicals may not only be hazardous to non-target living organisms but may move to other parts of the environment by various vectors [24]. The potential hazard of an agricultural pesticide as a ground7 water contaminant depends on its solubility, adsorption charac- teristics, and biodegradability [87]. A pesticide may be extremely toxic, but if its chemical composition is unstable, . is rapidly biodegradable or has a low solubility, it may not pose a hazard because it may never reach the groundwater. 39 ------- In general, pesticides used in agriculture can be grouped into five major classes. Each of these classes has certain phy- sical and chemical characteristics which are of primary im- portance in evaluating the potential hazard of such a class as a groundwater pollutant. These five classes of pesticides are: organic botanicals, organic phosphates, carbamates, chlorinated hydrocarbons (CH) and organometallic compounds. A brief discussion on the potential of each one of these classes for contaminated groundwater supply is given below. Chlorinated hydrocarbons are among the most stable of all pesticides in use today [28]. Some of the most noted pesti- cides of this group are DDT, aldrin, dieldrin, endrin, lin- dane, chlordane, heptachlor and toxaphene. These pesticides produce long-lasting toxic residues that are stable in a wide variety of environmental conditions. In some cases the residues or metabolites may be more toxic than the original pesticides. Chlorinated hydrocarbons are known to have extreme longevity [67]. Nash and Wilson (1971) reported that 39 percent of the origi- nal DDT applied to a test plot was recoverable after 17 years. Dieldrin was reported to be even more stable than DDT. Ter- riere (1956) investigated the persistence of various chlo- rinated hydrocarbons and concluded that dieldrin is the most persistent. The retention and releases of chlorinated hydro- carbon residues from soils is dependent on many factors. Temperature, soil type, and solubility of the pesticide are the most important factors. Studies in Wisconsin by Lich- tenstein (1962) suggest that persistence is also influenced by the chemical specificity of the insecticide, soil, moisture, cover crop, soil cultivation, mode of application and soil micro-organisms [97], Lichtenstein (1956, a) reported no residue release from chlo- rinated hydrocarbons where soils are frozen; under higher temperatures there is a positive correlation between tempera- ture and the amount of residue released from CH (chlorinated hydrocarbons). Swanson (1954) concluded that adsorption and not cation or base exchange was the principal mechanism in retaining lindane residues in soils. High organic content soils were shown to retain more CH residue than sandy or mine- ral soils. Similar results were obtained by Lichtenstein (1959, b). Wheatley (1960) determined that the half life of dieldrin in a mineral soil is approximately four years while the half life in an organic soil is approximately five to seven years. Thus, it can be concluded that the organic 40 ------- content of the soil is a dominant factor in the retention of CH pesticides residues. CH pesticide residue can be removed from soil by plants as was demonstrated by Wheeler (1967). A few microorganisms are capable of degrading dieldrin but the factors involved in microbiological degradation are complex and not well under- stood (Matsumura 1960). Due to adsorption processes in soil, the chlorinated hydro- carbons and their metabolites do not normally percolate into the subsoil [68]. However, in soils, such as montmorillonite, which are high in clays of an expanding nature, pesticides can be transported readily through the cracks which form in these soils during dry weather. Chlorinated hydrocarbons have been found as deep as 70 feet under these conditions [102]. Even though several of the chlorinated hydrocarbon pesticides have had their registrations cancelled in the U. Si, their residues may still be present because of their chemical sta- bility and therefore they may be a potential hazard to ground- water. The registration of DDT, aldrin, dieldrin, and endrin have been cancelled. Chlordane and heptachlor are presently being considered for cancellation. Contamination of groundwater by CH pesticide residue is de- pendent on their solubility in water as well as adsorption in the soil matrix. CH pesticides are considered to be only slightly soluble in water. Tests by the Georgia Agricultural Experiment Station [98] have shown that: (a) lindane was one of the most readily leached; 54 to 88 percent of this chemical was removed from six soils, (b) no trace of endrin was found in the leachate .from three soils but 51 to 95 percent of that added to the other three soils was leached, (c) dieldrin showed wide variability in behavior among six soils. Only 1 percent was leached from Magnolia sandy loam, whereas 65 percent was removed from Lakeland sand. Results from the other four soils were scattered in between these extremes, (d) Aldrin was very resistant to leaching. Only a trace was removed from five of the soils and 16 percent from the Lake- land sand, (e) Heptachlor also was very resistant to leaching. It is interesting to note that these results were obtained from six sandy soils found within a 50 mile radius of Tifton, Georgia. One can only conclude that a greater scatter in the results will occur if a wider range of soils obtained from different parts .of the United States is used. 41 ------- Eye [21] concluded that for one foot of penetration of die- Idrin residue level of 20 ppb, water must infiltrate a dis- tance of 360 to 480 feet into the soil. However, the number of cases where groundwaters were reported GH contaminated in the literature is minimal. It is difficult to estimate the degree of contamination of groundwater resources because well-water analyses of CH are not common. In addition, data on CH residue in groundwater is usually not reported in the literature unless it is a part of some particular study. • • > In view of the evidence reported in the literature surveyed it is likely that chlorinated hydrocarbon-pesticide residue can be a slight hazard to deep groundwater aquifers. However, in areas where shallow water table aquifers are present, a real potential hazard exists. i Carbaryl type pesticides containing nitrogen, .such as Sevin, break down in the soil in a comparatively short,time and the resultant metabolic products are non-toxic. No health hazards are known to exist from carbaryl pesticides at the present time [17]. • , , Triazine type heterocyclic pesticides such as diazinone and triazinone and their metabolites persist much longer in the soil [99]. Very little is known, about the metabolites of diazinones or triazinones with regard to toxicity or solu- bility. Chemical literature is still lacking on groundwater pollution by these pesticides. They have not yet been found to be groundwater pollutants. Organophosphorous and organosulfur pesticides are broken down easily and rapidly in soil and subsoil. These compounds are commonly called nonpersistent pesticides because they are degraded to less toxic compounds in a relatively short time (3-6 months, according to some studies) [102]. The degradation of these compounds is achieved by sunlight, soil bacteria, and water. Because of the instability of the original chemical structure and of the less toxic, biodegradable secondary compounds, it is unlikely that such compounds may contaminate deep groundwater sources. The time required for these com- pounds to reach deep groundwaters is sufficient for soil bacteria to attach and degrade them. Organometallic pesticides are those which contain metallic elements in the structure. There are spotty references to those toxic metals. More emphasis is put on arsenic- 42 ------- containing pesticides [41]. Arsenic reacts with the cations of iron, aluminum and calcium. These are water insoluble metallic arsenates which pose no health hazard to groundwater. The presence of phosphorous in the soil affects the phyto- toxicity of arsenic. Phosphorous and arsenic are in the same periodic group and hence have similar chemistry. Arsenic is removed from the soil by bacterial metabolism which transforms it into arsenic hydride and its methyl derivatives. These metabolites are gaseous and easily removed by volatilization. Many of the metallic elements in this group of pesticides have been found to persist in the soil and interfere with plant growth, but apparently pose little hazard to groundwater. Organic botanicals are pesticides derived from plant matter [28]. Such pesticides are manufactured either by extracting naturally occurring insecticidal compounds from plants or by grinding plant matter - roots, stems, leaves - of plants which contain certain insecticidal compounds. Because of their origin organic botanicals are quite low in toxicity, both to plants and warm-blooded animals. Their primary use is in home gardens and control of household insects. Although these compounds are widely used in households, they are of limited use in agriculture because of their high cost, very specific action and a tendency to deteriorate in storage. In general organic botanicals have low solubility in water and are ra- pidly biodegradable, a characteristic which will tend to limit their potential as a source of contamination of groundwater. Some of the common members of this group are nicotine sulfate, rotenone and pyrethrins. Only a limited number of instances of groundwater contami- nation by pesticides and herbicides have been reported in the literature. It is unlikely that groundwater contamination from these sources is a serious problem nationwide; as was pointed out earlier, only chlorinated hydrocarbons residues are persistent and therefore of concern [102]. A study con- ducted by Eye [21] concluded that for one foot of penetration of dieldrin residue at a residual level of 20 parts per bil- lion, water must infiltrate from 360 to 480 feet into the soil. Crosby [13] suggested that if an effective rainfall of about ten inches infiltrated a given area it would remove only 0.003 of a gram of dieldrin residue per square foot and transport it to a depth of approximately one-half inch. The soil for this case was sandy silt with about 20 percent clay. Because of the low solubility, partial degradation, uptake by plants,. biological attack, volatilization and co-distillation, con- tamination of groundwater sources by CH residue on a national 43 ------- scale is not believed to be a problem. However, in certain areas, local contamination of groundwater may occur; this would be primarily in areas of soils of very high permeabi- lity, high water table, and/or slow moving groundwater. Data on intensive farming regions where CH pesticides have been used heavily are available from standard sources (e.g., U. S. Census Bureau) and also through the U. S. Department of Agriculture, Federal and state agricultural experimental stations, agricultural extension services, and the EPA. The data on soils and hydrology can be obtained from the Soil Conservation Service, U. S. Geological Survey, USDA, state geological surveys, the Water Resource Department of each state, and the Water Resources Research Center of each state. The USDA's Agricultural Statistics is a particularly useful data source. B. Preliminary Correlation Between Organics Found in Drinking Water and Specific Pesticide and Fertilizer Uses The nationwide occurrence of organic compounds identified in drinking water are listed in Table 1-IV-l which follows [96]. Those which are active ingredients in pesticide formulations are listed in Table l-IV-2 and those which are inactive in- gredients, such as solvents, are listed in Table l-IV-3. The list of compounds in Table 1-IV-l comprise the total or- ganics identified in drinking water but are only a small fraction by weight of the total organics in drinking water [96]. Many of the chemicals which appear on Table 1-IV-l could be chemical or biochemical degradation products of pesticide formulations, both active and nonactive ingredients. There is no evidence of fertilizer ingredients. The majority of pesticides in drinking water arises from agricultural and urban runoff. A significant number of the chemicals listed on Tables l-IV-2 and l-IV-3 are chlorinated which is the more persistent category. To help put this matter of organic pesticide correlation with organics in perspective it has been determined that for one foot of pene- tration of dieldrin residue at a residual level of 20 ppb, water must infiltrate from 360 to 480 feet into the soil [103]. This throws some light on the likelihood the cor- relation which exists for surface water pesticides and or- ganics occurring for ground water. 44 ------- TABLE 1-IV-l Organic Compounds Identified in Drinking Water* acenaphthylene acetic acid acetophenone aldrin de ethyl atrazine behenic acid, methyl ester benzene sulfonic acid benzopyrene benzothiophene borneol bromochlorobenzene bromofonn bromophenyl phenyl ether butyl bromide e-caprolactam carbon tetrachloride chlorobenzene b-chloroethyl methyl ether chlorohydroxy benzophenone chloromethyl ether m-chloromitrobenzene o-cresol DDT dibromobenzene dibromodichloroethane 1,4-dichlorobenzene 1,2-dichloroethane dieldrin di(2-ethyl hexyl) phthalate dihydrocarvone di-isobutyl phthalate 1,3-dimethyl naphthalene 2,4-dimethyl phenol acanaphthene bladex chlordene crotonaldehyde cycloheptanone acetaldehyde acetone acetylene dichloride atrazine barbital benzene benzoic acid benzothiazole benzy butyl phthalate bromobenzene bronodichloromethane bromoform butanal butyl benzene camphor carbon disulfide chlordane 1,2-bis-chloroethoxyethane chloroform b-chlorethyl methyl ether chloromethyl ethyl ether 3-chloropyridine DDE decane dibromochloromethane dibutyl phthalate dichlorodifluoroethane dichloroethyl ether diethyl phthalate dihexyl phthalate di-isobutyl carbinol 1,2-dimethoxybenzene dimethyl sulfoxide dimethyl phthalate benzaldehyde carbon dioxide 1-chloropropene cyanogen chloride 1,3-dichlorobenzene *Source: "Identification of Organic Compounds in Effluents from Industrial Sources" Prepared for Office of Toxic Substances - EPA Prepared by Versar Inc., Springfield, Virginia April, 1975, EPA 560/3-75-002 45 ------- 1,l-dichloro-2-hexanone dichloropropane di-(2-ethyl hexyl) adipate diphenyl hydrazine p-ethyl toluene hexachlorophene methyl methacrylate pentachlorophenyl methyl ether propazine trimethyl benzene o-xylene m-xylene alachlor butyl octyl maleate ethyl acetate 1,1,1-trichloropropane methyl-2,3-dihydroindene tetrachlorophenol methyl cyclohexane diraethoxy acetophenone o-phenyl phenol tetramethyl benzene trichloropropane dichloroiodomethane bis-(2-ethoxy ethy) ether chloroiodomethane Acetylene chloride isopropanol chloroethyl ether 4,6-dinitro-2-aminaphenol dioctyl adipate docosane eicosane ethanol ethyl benzene cis-2-ethyl-4-methyl-l,3- dioxolane o-ethyl toluene heptachlor 1,2,3,4,5,7,7-heptachloronor bornene .hexachloro-1,3-butadiene hexachloroethan 2-hydroxadiponitrile .isodecane isoborneol isopropyl benzene methyl ester of lignoceric acid methanol methyl benzoate 2,4-dichlorophenol 1,3-dichloropropene diethyl benzene m-ethyl toluene geosmin o-methoxy-phenol methyl tetracosamoate piperidine simazine 3,5,5-trimethyl-bicyclo-(4,1,0)- heptene-2-one p-xylene butachlor dicyclopentaciene pentachloroethane 2,3-dihydroindene methyl benzothiophene ethyl hexanol ethyl acetophenone 2,6-di-t-butyl-4-methylphenol butyl benzene sulfonamide isocyanic acid trichloropropene chloral bromomethane chloropropane bromotrichloroethylene biphenyl diethyl ether 2,6-dinitrotoluene dipropyl phthalate n-dodecane endrin ethylamine 2-ethyl-n-hexane trans-2-ethyl-4-methyl-l,3- dioxolane guaiacol heptachlor epoxide hexachlorobenzene hexachlorocyclohexane hexadecane indene isophorone isopropenyl-4-isopropyl benzene limonene methane. 2-methoxy biphenyl methyl benzothiazole 46 ------- methyl biphenyl methyl chloride 2-methyl-5-ethyl-pyridine methyl naphthalene methyl phenyl carbinol methyl stearate naphthalene nitrobenzene octadecane octylchloride pentachlorophenol pentane phenyl benzoate propanol propyl benzene 1,1,3,3-tetrachloroacetone tetrachloroethane toluene trichlorobiphenyl 1,1,2-trichloroethylene 2,4,6-trichlorophenol l,3,5-trimethyl-2,4,6-trioxo- hexahydro-triazene vinyl benzene 3-methyl butanol methyl ethyl ketone methyl indene methyl palmitate 2-methyl propanal methylene chloride nitroanisole nonane octane pentachlorob ipheny1 pentadecane pentanol phthalic anhydride propylamine 1-terpineol tetrachlorobiphenyl tetrachloroethylene trichlorobenzene 1,1,2-trichloroethane trichlorfluoromethane n-tridecane triphenyl phosphate n-undecane xylene 47 ------- TABLE l-IV-2 Pesticide Chemicals Identified in Drinking Wnter Active Ingredients [94] acenaphthylene acetic acid aldrin atrazine (de-ethyl)atrazine bromoform carbon disulfide carbon tetrachloride chlordane chloroform DDE DDT 1,4-dichlorobenzene dichlorethyl ether dieldrin 4,6-dinitro-2-aminophenol endrin heptachlor heptachlorepoxide 1,2,3,4,5,7,7-heptachloronor- bornene hexachlorobenzene hexachlorocyclohexane isophorome naphthalene pentachlorophenol 2,4,5-trichlorophenol 48 ------- TABLE l-IV-3 Non-Active Ingredients of Pesticide Formulations Identified in Drinking Water [94] acetone benzene benzoic acid camphor chlorobenzene o-cresol dibutyl phthalate dimethyl benzene (xylene) 2,4-dimethyl phenol dimethyl phthalate dimethyl sulfoxide ethanol hexachloroethane 1imonene methanol (3-methy1-2-butane) methyl chloride methyl ethyl ketone methyl naphthalene (methylated naphtalenes) methyleve chloride nitrobenzene pentane propanol 1-terpineol tetrachloroethane tetrachloroethylene toluene (1,1,1-trichloroethane) 1,1,2-trichlorethylene trichlorofluromethane xylenol 49 ------- ingredients should not be considered comprehensive not only because of the lack of information on degradation products but also because of the possibility of the presence of un- reacted pesticide raw materials. In addition many of the pesticide ingredients are also potentially derived from in- dustrial, medical, and natural environmental sources. It should not be inferred from this correlation presentation that the presence of pesticide chemicals and/or their degra- dation products in drinking water is explained by pesticide pollution of groundwater nor is the inference intended that the presence of these chemicals in drinking water does or does not lead one to the conclusion that they can be expected to be found in groundwater because of the characteristic flow patterns which relate groundwater and surface water. C. Laboratory Testing Procedures for Pesticides There is a definite need in some areas for laboratory work to supplement the statistical data available. This is especially true in areas where edaphic and hydro-geologic factors are unique and conducive to pesticide transport into groundwater. Areas where data is marginal but show a need for further investigation should be sampled. Analytical methodology for determination of pesticide residues and their metabolites and degradation products in environ- mental samples is in a state of constant development with rapid advances in analytical chemistry and instrumentation. There are several analytical methods available for pesticide residue analysis. At present, the most accurate and most advanced method available is gas-liquid chromatography. In the discussion of laboratory analysis, gas chromatography will be considered as a prime tool for pesticide residue analysis. If and when analysis warrants other methods to supplement gas chromatography, these more suitable methods should be em- ployed. All methods and procedures must follow the procedures de- scribed and published in the Association of Official Analy- tical Chemists (AOAC) [23]. The Food and Drug Administration, Environmental Protection Agency, and the Agriculture Research Service of the USDA all follow the AOAC. By strictly fol- lowing the methodology of AOAC the data obtained will be within the limits and variables of data published by the above mentioned agencies. The procedures for processing and analyz- ing samples are given in the AOAC manual. Laboratory testing procedures are highlighted below. 50 ------- Gas Chromatography. It is necessary to use preparative thin layer chromatography to separate and isolate pesticide resi- dues from other contaminants. A pesticide residue separated from other contaminants should be analyzed using gas-chroma- tography equipped with electron capture detectors for its quantitative determination. Injection technique and injection is one of the important starting functions of the gas chromatographic analysis. It is important that both standard and sample solutions be handled in precisely the same way in order to minimize errors caused by variable response of the instruments. It is also important that sample injection be carried out at least twice, as should be standard, to minimize errors. Only glass columns should be used since they minimize de- composition. These columns must be conditioned at an elevated temperature before use. All columns will be standardized with various standard samples to check their efficiency and reli- ability. Electron capture detection with a tritium source should be employed since these types of detectors are most accurate. When necessary, the tritium foils can be changed easily. The areas under the peaks of the sample graphs and the stand- ard graphs must be calculated in an identical manner so as to minimize measuring errors. There is probably no need for nitrate determination in the laboratory. Sufficient published data is available at present to define and assess the problem. > Time and Temperature. Samples should be analyzed as soon as they are received in the laboratory. This will minimize physical and chemical changes that may occur. A waterless sample must be stored below 0°C in airtight glass bottles. Since light has an effect on pesticides and they do degrade under exposed light, samples must be kept in the dark and in amber colored glass bottles. It is necessary to avoid plastic or metal containers for storing samples, since they affect the pesticide concentrations or cause contamination. The caps used on the amber storage bottles should be equipped with teflon liners to prevent contamination. Extraction Methods. A standard method of extraction should be employed to get the sample free from water and soil particles. Standard techniques such as blending or tumbling of the sam- ples and solvents for rapidity and ease of handling 51 ------- should be employed. A mixture of relatively polar and non- polar solvents has to be employed to get a thorough extraction of the pesticide residue. Cleanup Procedure. It is necessary to use the standard clean- up procedure before GLC analysis. This should be done for two reasons. First, a cleaned sample will give specificity and ease of analysis, and secondly it will prevent undue con- tamination of gas chromatograph injection ports, columns, and detectors. V. ECONOMIC IMPACT OF GROUNDWATER CONTAMINATION ABATEMENT A. Introduction and Overview The approach which is proposed to the evaluation of the econo- mic effects of the regulation of groundwater contamination is related to cost-benefit analysis. This interconnection is important for two reasons. One is the legitimacy conferred on the suggested procedure through its compatibility with the generally-used and officially-suggested cost-benefit tool.* The second reason is that the cost-benefit framework is a useful one for clarifying the assumptions underlying the suggested economic impact analysis. Explanation of these interrelationships and assumptions should therefore introduce the economic evaluation of the regulation of groundwater contamination. B. Cost-Benefit Analysis Cost-benefit analysis is the generally-accepted current prac- tice used for the economic evaluation of public programs. As Mishan argues, cost-benefit analysis is not fundamentally different from the accounting for profitability employed by a private firm when considering an investment in the production of goods or services. Rather, the same sort of question is being asked about a wider group of people—who comprise so- ciety—and this question is being asked more searchingly. Instead of asking whether the owners of the enterprise will become better off by the firm's engaging in one activity rather than another, the economist asks whether society as a whole will become better off by undertaking this project rather than by not undertaking it, or by undertaking, instead, any of a number of alternative projects [36]. "*Senate Document 97 encourages the use of cost-benefit analysis in public decision-making. 52 ------- A critical part of any economic evaluation is the careful delineation of the relevant costs and returns. James and Lee categorize the benefits and costs associated with water re- source planning [48]. In addition to the (a) tangible primary benefits gained directly from project-produced goods and services—examples are irrigation water and flood control— James and Lee categorize benefits as (b) tangible secondary, including gains accruing to output-receiving and input-pro- viding industries interrelated with the directly-affected industry groups (c) tangible employment benefits (d) tangible public benefits and (e) intangible benefits. Tangible employ- ment benefits are the new jobs created to construct, maintain or operate the project. Tangible public benefits include such often serendipitous gains as economic stabilization, income redistribution, and regional development. C. Intangible Benefits Intangible benefits are consequences which cannot be assigned market value and which must be evaluated on a judgmental basis. Examples are the saving of life, improvement of health and the preservation of a desirable environment. Because these benefits involve value judgments, authors like James and Lee typically have less to offer about assessing them. The above list of benefits shows the disadvantages of standard cost-benefit analysis for the assessment of the regulation of groundwater contamination. The benefits from such regulation are primarily intangible. They are also future-oriented. Groundwater typically moves slowly and is contaminated as a result of a long-term and gradual process. Once contaminated, nature's ability to cleanse the water is also slow (or even non-existent). This long-term situation means many,of the most significant benefits from regulation of contamination accrue to future populations rather than to the current so- ciety. Intangible benefits from maintaining pure groundwater are quite complex as well as very important. Economists like Weisbrod, Cicchetti, Freeman, Aaron and Fisher have identified at least four different "option values" for such forms of regulation. One of these, "option demand," is the value to . individuals of having future access to a resource for economic. uses. A second option value, "existence demand," is the demand of people who do not ever plan to use a resource, but. who derive value from knowing it is preserved in its natural • state. "Bequest demand," the third option value, is a derivative 53 ------- . of option demand in which individuals wish to guarantee the option of using a resource for their heirs. Finally, there is "safety or hazard-aversion demand" from individuals who want to avert the risk of damage to their health. - All four option values result from the regulation of ground- water contamination. However, it is doubtful these values could ever be separated empirically, much less assigned a quantitative value. Furthermore, if one were to attempt to measure the various benefits as outlined by James and Lee, regulation of the contamination of groundwater would.usually end up with a negative quantitative benefit value and a set of qualifying statements. Such a statement of benefits runs a risk of misinterpretation by anyone who does not read the report with care. D. Economic Impact Analysis Negative benefit values do not invalidate" cost-benefit analy- ses, but they do make such analyses awkward to handle. Con- sequently, economic analysts often shift away from cost- benefit analysis in such cases, and use economic impact analysis instead. Economic impact analysis starts with the a- priori presumption that the benefits are great enough to justify the public program. The goal of the analysis becomes the assessment of the costs of the program. Costs are not restricted to the direct and ^associated costs of the* project's construction as they are in cost-benefit analysis. Rather, costs are defined to be the costs of cost-benefit analysis plus any quantifiable negative benefits. A major purpose of doing an economic impact analysis is to allow the initial assumption of the worthiness of the public program to be re- evaluated via a more informed judgment. It is suggested here, and later in the "plan" section, that economic impact analysis best suits the economic analysis of the regulation of groundwater contamination. Such an analysis provides a suitable analytical context which is consistent with cost-benefit analysis and which is clear in interpre- tation. The framework of the approach emphasizes the central and a-priori nature of the judgment made about the intangible benefits and it encourages the re-evaluation of -this judgment. In the suggested economic impact analysis, costs would be defined as primary and secondary. Primary costs would be those incurred by the directly-regulated firms or households in complying with the.regulation. Secondary costs are the negative secondary, employment and public benefits expressed as positive quantities. Any positive tangible benefits 54 ------- would, of course, be subtracted from these secondary costs. The costs used in the impact analysis would be expressed as marginal values. Only the increase due to the introduction of the regulatory program would be measured. This allows the cost to be viewed as an impact. Also, it often simplifies the technical derivation of the cost coefficients. E. Primary Costs Some of the techniques which could be used to measure primary costs at the firm or household level are partial budgeting, mathematical programming and economic engineering analysis. These techniques have a comparative advantage over other econometric methods at this level of dis-aggregation. Partial budgeting has the additional advantages of simplicity and un- expensiveness; however, its use depends on the availability of good accounting data. Mathematical programming can yield the same type of answers as budgeting plus additional results, but this more formal method is better suited for optimizing re- turns than for assessing impacts. Economic-engineering— called unit operation analysis by engineers—has an advantage whenever the costs of new productive enterprises are needed and the necessary accounting data is not available. F. Secondary Costs Primary costs would have to be determined at the firm or household level and then aggregated to a regional level by using firm and household distributions. Secondary costs can be measured at the regional level via such techniques as input-output analysis, economic base analysis, social ac- counting techniques or by consumer and producer surplus mea- sures of social welfare. Input-output analysis and economic base analysis focus on the costs incurred by industries that are economically linked to the regulated firms and households. The consumer-surplus oriented method focuses on the impacts on final consumers and on the suppliers of labor. All of these more formal methods are time-consuming, expensive and data- demanding. Yet they do not always incorporate all the secon- dary cost factors. As a consequence, they should be used only when a particular secondary cost is so significant that care- ful formal measurement is necessary. The inter-relationships of the various measurement techniques will be more clearly specified in the tasks outlined later. It should be noted, however, that these tasks stress a careful and sometimes elaborate delineation of which primary and 55 ------- secondary costs are important as the quantification .of a particular cost. Also, the proposed tasks stress simplicity of measurement, whenever possible, with the more complicated and expensive methodologies .relegated to a back-up role. The keynote.criterion of the proposed procedure is a uniformly accurate measurement of all significant costs. Such an ap- proach should adequately serve the need for an economic eva- luation of the regulation of groundwater contamination. VI. GROUNDWATER FLOW MODELS A. Introduction and Overview Porous soil media is a complex matrix. Such a matrix may be viewed as a solid body with irregular interconnected voids. These interconnecting voids or pore channels are of primary interest in understanding the flow of miscible fluids in porous media. There are two approaches to the study of flow through porous media; the investigation of the particular porous media matrices that exist in nature, or the mathe- matical modeling of various types of matrices. Experimen- tally, the investigations would be limited to a small number of different porous media matrices; with theoretical model studies many different possible porous media structures could be investigated. However, the validity of the theoretical model must be assured through experimental verification. Experimental techniques have been carried out to a-high degree of refinement. Generally, a .given substance is.injected into the medium, and then the medium is sampled at various, depths by cutting into it or extracting liquid from it for analysis. Theoretical modeling includes two distinct.approaches (a) the deterministic model, and (b) the probabilistic model. The deterministic model is based on the solution of the basic differential equations for viscous fluids subject to dis- persion and adsorption. The probabilistic models on the other hand concentrate on the statistical character of the porous media. The present state of the art of analytic - numerical methods for solving particular flow problems in porous media flow is to solve a set of coupled nonlinear partial diffe- rential equations with appropriate boundary and initial, etc. conditions. In dealing with the movement of pesticides and nitrates from the soil surface down to the water table one must look at flows in the unsaturated region as well as flows in the satu- rated region.. The unsaturated-region consists pf the 56 ------- layers overlying the groundwater table; in this region the soil pores are filled by two materials - water and air. Water movement in these layers consists of three phases -solid mineral grains, fluid water and gaseous air. The transport of water is more complicated in this region than it is in the saturated region (region below the water table) where the soil pores are completely filled with water. B. Unsaturated Flow In the unsaturated region the infiltration process is a com- plex phenomenon. It consists of a hydraulic transfer of water, accompanied by extraction, and subsequent retention, of liquid by the sediment as the infiltrating liquid passes through it. For example, the water retention in gravel is negligible, while in sands the retention is due primarily to capillary action. In clays, however, the retention, which is essentially an osmotic pressure mechanism, is very large. The shrinkage cracks in a dry clay result in large amounts of water being transmitted. This lasts until the dry matrix has swelled and closed up, at which time the clay ceases to trans- mit appreciable amounts of water. From these considerations it appears that sediments or soils consisting of gravel, sand and silt are, in addition to fissured rocks, make up the principal soil formation capable of transmitting substantial volumes of water and contaminants into groundwater basins. As .stated earlier, the mathematics of flow in the unsaturated media is extremely complicated. In only a few cases have solutions been obtained. These solutions were obtained using one-dimensional, two-dimensional, and simplified models. Little is known of the adsorption mechanism of pesticides on soil matrices. Experimental studies indicate various amounts of CH are leached from different soils. In summary, knowledge of moisture movement in the unsaturated zone is not advanced to the stage where one can accurately predict transient mois- ture changes under actual field conditions; complete models that accurately predict migrations of various pesticides and nitrates in the unsaturated zone have not been fully deve- loped. C. Saturated Zone The theory of dispersion of miscible fluids in porous media has received considerable attention in recent years. Interest in dispersion has resulted from water quality considerations of waste disposal operations, sea water intrusion and seepage from canals into aquifers. 57 ------- Hydrodynamic dispersion or miscible dispersion is a spreading phenomenon. Experiments show that when a flow containing a certain mass of solute (known as a tracer) is moving, the tracer usually spreads and occupies an ever increasing portion of the flow domain, beyond the region it Is expected to occupy according to the average flow alone. The mixing of the tracer mass with the remaining portion of the flowing liquid is a transient, irreversible process. Hydrodynamic dispersion is the macroscopic outcome of the actual movements of the in- dividual tracer particles through the soil pores and also the outcome of various physical and chemical phenomena that take place within the pores. The two basic transport phenomena involved in dispersion are convection and molecular dispersion. The two basic elements of convection or mixing are the flow (variation in local velocity, both in magnitude and direction) and the geometry of the pore system. Molecular dispersion is a mass transport phenomenon resulting from variations in the tracer concent- rations within the liquid phase. The interaction between the solid surface of the porous matrix and the liquid may take several forms: adsorption of tracer particles on the solid surface, deposition, solution, ion exchange, etc. [38]. All of these phenomena, as well as chemical reactions within the liquid, may cause changes in the concentration of the tracer in the flowing liquid. Because of the complexity of the dispersion-adsorption pheno- menon in porous media, no general model has been formulated and solved. Solutions to various specific miscible displace- ment problems in porous media have been obtained by a number of investigators. Common to most of these studies is the basic assumption that the concentration at one boundary is in the form of a step function; that is, the concentration of the tracer to be introduced at one boundary changes instantane- ously from zero to some predetermined value and is maintained thereafter (conservative model). In addition, most models assume that convection and dispersion are the principal fac- tors in mass transport while other mass transport mechanisms are considered insignificant and therefore neglected. The model studies which have been performed by various in- vestigators can be placed into one of two categories: (a) dispersion with no adsorption, and (b) dispersion with ad- sorption. A brief summary of each type of modeling is given below. 58 ------- D. Dispersion With No Adsorption Some of the early analytical solutions for longitudinal dis- persion within a semi-infinite non-adsorbing porous media were obtained by Ebach, et al (1958) and Ogata, et al (1961). In both cases, a steady undirectional flow was assumed; the Ebach study assumed an input concentration that is a periodic func- tion of time while the Ogata study considered the 1 input concentration to be a constant. Hoopes, et al (1965) investigated the problem of dispersion in radial flow from a fully penetrating well operating in a homogeneous, isotropic confined aquifer. The study was directed primarily at dis- persion from injection wells where the solute was non-ad- sorbing. Shamiz, et al (1960) obtained analytical solutions for longitudinal dispersion in a semi-infinite non-adsorbing layered medium. In their model, the flow was assumed to be perpendicular to the layers of longitudinal dispersions and parallel to the layers for the lateral dispersion case. In both cases the input concentration was assumed to be constant and adsorption was neglected. Bruch and Street (1966) in- vestigated the flow in a semi-infinite non adsorbing porous media subject to longitudinal and lateral dispersion. As in the previous studies, it was assumed that there is steady undirectional flow which was subject to a constant concent- ration input. E. Dispersion With Adsorption Nielsen, et al (1962) presented several examples of break- through curves in which interaction between the liquid and the solid phase has taken place. Several theoretical models have been suggested for dispersion with adsorption. Lindstrom, et al (1967) examined various solutions to the dispersion equat- ion subject to linear adsorption under input conditions of continuous flux and plug type. Ogata (1964) obtained an analytical solution to the one dimensional dispersion equation subject to linear adsorption. Similar solutions were also obtained by means of the integral transform method by Cleasy and Adrian (1973). Banks and Ali (1964) presented an analy- tical solution to the dispersion equation subject to a linear adsorption isotherm. The flow was considered to be steady and one-dimensional under a constant concentration input. The case of non-linear adsorption was also investigated subject to. no dispersion. Gershon, et al (1969) studied the effects of boundary conditions of various models on tracer distribution . in flow through porous media. A solution for one-dimensional • dispersion subject to a semi-infinite adsorpting porous media was presented. 59 ------- Numerical solutions of the dispersion equation for different adsorption equilibriums was reported by Lai, et al (1972). Solution to the one dimensional dispersion equation subject to non-linear adsorption was given by Tagamets, et al (1974), and by Gupta, et al (1973) for a bilinear rate of adsorption. Solution of the dispersion equation with adsorption was also reported by Rubin (1973). A summary of some analytical so- lutions to the dispersion equation is given by DeWiest (1969) and Ogata (1970). F. Summary of Dispersion Models In general, the available analytical solutions of.the dis- persion equation are for simple one dimensional flow with constant concentration input. In all of these cases adsorp- tion has been neglected or assumed linear. The available numerical techniques provide approximate solutions for dis- persion with non-linear adsorption in one dimensional flow. All of the above cases are ideal, i.e. homogeneous, isotropic soils, constant initial concentration, and well defined ad- sorption isotherms. Unfortunately, conditions in nature cannot be duplicated by the models; soils are not homogeneous and isotropic, concentration varies with time and space, and the adsorption isotherms of many pesticides are not well known. C. Regional Models A physical-chemical model for predicting the movement of contaminants in an isothermal groundwater system in which there are no chemical reactions was developed by Bredehoeft and Finder [5, 6]. The mass transport equation and the equa- tion of motion have been coupled and solved numerically for a saturated groundwater system. The authors tested their model by analyzing the movement of contaminants in the principal aquifer at Brunswick, Georgia [59, 60]. The particular contaminant studied was salt water contamination (chloride) and the model was used to predict future chloride distributions. The model was calibrated using data available due to extensive geohydrological investigations conducted by USGS at Brunswick. The use of this.model to predict changes in ground water quality is limited. The complete physical - chemical description of moving groundwater must include chemical reactions in a multicomponent fluid and requires simultaneous solutions of the differential equations that describe the transport of mass (including dispersion, adsorption) momentum and energy in porous media. Finder [55] used the Galerkian method in conjunction with the finite element method to simulate the movement of groundwater con- taminants. The mathematical model was used to simulate the 60 ------- movement of a plume of chromium contaminated groundwater on Long Island, N.Y. The two dimensional model considered poro- sity and hydrodynamic dispersion to be the principal aquifer properties affecting mass transport. Values of longitudinal and lateral dispersion were estimated based on tests conducted on similar material due to lack of actual data. Adsorption was neglected in this study. Calibration of the model was based on historical record of chromium distribution and was used to predict the location of the plume in future years. The model requires extensive data and is limited to cases where the point where the effluent concentration enters the aquifer is known. In 1974 a digital computer program [22] was developed to esti- mate concentration of total dissolved solids (TDS) of ex- tracted water from a multiaquifer groundwater basin. The model considered salt input from natural sources due to man's uses of water: domestic, industrial, and agricultural. The model was tested on the Santa Clara - Calleguas area in Ven- tura County, California. That area was selected because a water quality model was already available for the area and could be used to simulate groundwater movement. The quality model considers six inflows such as rainfall infiltration, percolation, etc. and three outflows: sub- surface outflow, extraction and consumption by phreatophytes. The model does not account for chemical reactions, adsorption of dispersion. It is basically a tool for management to predict TDS concentration subject to different inflow para- meters. During 1974 the U.S. Geological Survey (USGS) [61,53] com- pleted a study, wherein a conservative model was developed. The linear mathematical model used in the USGS study is an idealized representation of the San Juan Valley groundwater basin. It describes in concise quantitative terms the re- sponse of the groundwater system to various conditions of stress or development. Once such a quantitative response has been obtained, the model can be used to facilitate an under- standing of the hydrologic system and aid in determining how climate, geology, and man influence the groundwater basin. The model was developed according to the theory and analytical approach developed by Finder and Bredehoeft [5], (1968) [6]. In order to use this mathematical model as a predictive tool . it must first be calibrated. Model calibration is accomplished 61 ------- by combining, in the model, hypothetical distributions of transmissivity and specific yield values with sets of known or estimated groundwater flow conditions. The correct, or cali- brated, combination of aquifer parameters and flow conditions is determined when model-generated water levels approximate historical water levels within some predetermined limit of accuracy. Recently the Agricultural Research Service of the USDA pub- lished an Agricultural Chemical Transport Model (ACTMO) [25]. The objectives of this model are to predict the concentration and amount of the chemical in the runoff water and in the sediment at the watershed outlet, and to predict the location and concentration of chemicals that are leached and moved spatially through the soil of the watershed. The model in- cludes such management options as the time, rate, and type of chemical applied, changes in crop pattern, and tillage prac- tices. To facilitate application, topographic, soil, and land use maps of the watershed are used to estimate model para- meters. The model's authors assume that published, data from the field and laboratory can be used for estimating the chemi- cal interaction with the soils and water. The model is divided into three submodels: a chemical, an erosional, and a hydrological submodel. The erosion submodel receives data from the hydrology submodel while the chemical submodel receives data from both the hydrological and ero- sional submodels. This separation facilitates the interchange of other chemical, erosional or hydrological submodels and modifications. Objectives of the initial effort were to achieve an operating version of ACTMO for certain limited conditions. Unfortunately, ACTMO which is a dynamic model, is aimed pri- marily at surface water runoff from a specific farm. However, it could be modified to reflect the groundwater recharge problem, and by manipulating and adding parameters, it could be used over large section of soil regions. A model, called the Pesticide Transport and Runoff (PTR) Model [12] was developed by the EPA. This model is primarily a surface model, but like ACTMO it gives results adaptable to groundwater needs. Four pesticide storage zones with assigned depths within the soil profile are assumed:, surface zone, upper zone, lower zone, and groundwater zone. The assumed . zone depths are necessary to specify the mass of soil involved in the pesticide-soil interactions. The PTR Model estimates the loss of pesticides from the land surface by simulating the mechanisms of surface runoff, 62 ------- sediment loss, pesticide adsorption-desorption, and pesticide volatilization and degradation. There are various loss mechanisms and submodels included within the PTR Model. The hydrologic submodel is responsible for the determination of surface runoff and soil moisture storage. The sediment loss submodel estimates sediment production from the land surface based on input rainfall and surface runoff provided by the hydrologic model. The division of applied pesticide among the various phases (adsorbed, dissolved, and crystalline) is determined by the pesticide adsorption-desorption submodel. This submodel, in conjunction with the hydrologic and sediment loss submodels, determines the amount of pesticide removed from the land surface by surface runoff and sediment loss. This model also considers the loss of pesticides by vola- tilization and degradation. Another recent model [14] developed for the EPA describes pesticide movement through soils. In this work a numerical simulation procedure for describing the simultaneous transport of water and adsorbed and nonadsorbed solutes was developed and evaluated. The combined effect of convection, adsorption- desorption, and dispersion (diffusion and mechanical dis- persion) were considered as well as a correction for numerical dispersion in the finite difference solution of the solute transport equation. Experimental laboratory and field data were used to evaluate the suitability of the two numerical solutions to describe the movement of each phase. Adsorption and desorption was also studied for several herbicide-soil systems. Several adsorption models were considered and eva- luated in the solute transport equation. However, a numerical solution has not been developed and tested for simultaneous transfer of water and adsorbed solutes in a soil. > It appears that, given reasonable time to develop or modify subsections from existing models, a working model could be developed which would describe the percolation of nitrates and/or pesticides through various soil types and into ground- water. Although such a model can be developed, there are two obstacles which potentially limit the usefulness of the model: (a) the amount of data available for input into the model; and (b) the surface area over which the model can be applied. The PTR and ACTMO models can now characterize only a few acres of surface, which indicates the degree of difficulty still to be met in modeling larger areas. The EPA laboratory at Athens, Georgia, is developing a water basin study using an area of approximately twenty square miles in Iowa [103]. This region will be instrumented and 63 ------- modeled for surface and subsurface runoff evapotranspiration, rainfall, crop cover, soil porosity and moisture, pesticide (and fertilizer) applications, rates of denitrificatibn, etc. An estimate will be made as to How much water percolates through the soil as part of the materials balance, but a measurement of the effects on groundwater as such are not projected at present. It would seem feasible that this multi- year study could be modified to include considerations of groundwater, and the model extended to include this dimension. Putting this project in perspective, one of the intents of this study is to give the EPA and the manufacturers of pes- ticides a "standardized" method for calculating the potential impact of a pesticide on surface waters before registration is granted. The U.S. Geological Survey and certain contracting firms have developed models [60] for the U.S. Energy Research and De- velopment Administration (formerly the U.S. Atomic Energy Commission) which characterize the transport of radioactive and chemical wastes from buried materials. Reeves and Duguid [16,58] have developed a two-dimensional transient model for water movement through saturated-unsaturated porous media which can cope with multi-layered geologic formations. This model uses the Galerkin finite-element method. With these point source models available, it appears feasible that with additional submodels included, a feedlot (or septic system) could be adequately modeled to estimate groundwater impacts. Many other models have been developed and come to our atten- tion, but an extensive evaluation of each model at this point is not in order. Such' an effort, however, has been assigned by EPA (Ada, Oklahoma) to the Commission on Simulation Mo- deling of the Scientific Committee on Problems of the Environ- ment, headed by Drs. Frenkiel and Munn [64]. This project, titled "Evaluation of Existing Groundwater Basin Management Models," is funded in part by EPA under project control number R803713-01. This project is directed to the EPA program catalogue number and title 66.505 Water Pollution Control- Research Development and Demonstration. This year long effort is expected to be completed in late Spring-early Summer of 1976. The objective of this study is to evaluate existing ground- water basin models in order to judge the state of knowledge and state of the art in this,complex art-technology. The intent is to provide guidelines for future modeling develop- ment work to insure a sound and logical baseline. Indirectly, 64 ------- the project may provide guidelines for optimizing the design of monitoring networks. It is,strongly suggested that there be a high level of inter- change between this committee and the EPA task force concerned with groundwater modeling efforts in order to more rapidly implement the findings of other groups already working in this field. 65 ------- THE IMPACT OF INTENSIVE APPLICATION OF PESTICIDES AND FERTILIZERS ON UNDERGROUND WATER RECHARGE AREAS WHICH MAY CONTRIBUTE TO DRINKING WATER SUPPLIES Section 2 Approaches For A More Detailed Investigation I. INTRODUCTION This study has considered major agricultural practices with regard to their possible adverse impact upon groundwater recharge areas. Information has been gathered from many sources including lite- rature search, interviews, personal communications and review of other related studies and investigations. In the light of current knowledge, it is apparent that all of the complexities and inter- relationships of the many facets of groundwater pollution are not yet fully comprehended. Therefore, a set of tasks has been formulated which illustrates an approach to better understand the total problem and would pro- vide a basis for judging the need for measures of abatement and control. These tasks and any further work on the problem will be considered within the context of competing priorities for ful- filling the charges under the Safe Drinking Water Act. These tasks, which could be carried out in a period of about fifteen months, have been carefully defined to avoid duplicating efforts completed or in progress elsewhere. A considerable effort is already underway at various institutions pertaining to the broad topic of intrusion of toxic substances into groundwater from the use of such chemicals and also from the operation of feedlots and septic systems. The related problem (not dealt with in this study) of saline buildup, in connection with irrigation practices, is also under extensive investigation. The results of these studies will provide inputs to the various tasks described here below. Some tasks do complement work already carried out, but are included here in order to broaden or fill-out these other projects. Tasks which require very long term efforts, even though potentially valuable, have not been included; also projects of marginal payoff have been omitted. A set of econometric tasks, in which the costs and rewards of optimal corrective measures would be evaluated, 66 ------- illustrates an approach to defining the financial impact and/or justification of any recommendations ultimately considered by the Agency. Some of the proposed tasks are common to, or impinge upon, topics under consideration, whereas others are germane only to specific components, such as pesticides, fertilizers, feedlots, etc. The presentation, therefore, is structured into "activity streams" (Figure 2-1-1) in which the investigations may be conducted con- currently. Four major subject areas are considered: 1. Nitrates o Fertilizers o Feedlots o Septic Tanks 2. Pesticides 3. Economic Impacts 4. Modeling and Simulation The "general" activity stream (Tasks G-l, G-2, G-3, et seq) is designed to generate basic information relatable to all three sources of nitrates and to pesticides. A separate activity stream is then pursued for fertilizers (Tasks FR-1, etc.) feedlots (Tasks FE-1, etc.), septic tanks (Task S-l, etc.), and pesticides (Task P-l, etc.) and finally all five streams are brought together for the economic impact (Task E-l) and modeling (Task M-l) activities. In the following pages, the objectives, scope and technical ap- proach to each set of tasks are described. To support and illu- minate these descriptions, a detailed discussion of each subject area and the present state of knowledge in each is given in a series of appendices to the plan. II. GENERAL A. Task G-l Objective: To identify and map those areas of the country which may be vulnerable to groundwater contamination from agricultural practices. Scope; The nation's systems of groundwater reservoirs are influenced by climate, soil characteristics, depths of im- pervious layers, water tables, and other factors. Those areas in which major productive aquifers occur, i.e., aquifer whicfi can yield more than 50 gallons of water per minute to the public water supplies are to be located and identified, in terms of their vulnerability to contamination. 67 ------- 00 FEEDLOTS FERTILIZERS GENERAL PESTICIDES SEPTIC TANKS RECOMMENDED MEASURES FOR CONTROL Figure 2-1-1 Activity Streams ------- Approach; From data available through such agencies as the U.S. Geological Survey (USGS), State Water Resource Research Centers, U.S. Department of Agriculture (USDA), U.S. Environ- mental Protection Agency (EPA) and others, a map will be prepared to show those areas where public water supply is drawn from groundwater reservoirs which are most vulnerable to contamination by virtue of being overlain with thin or sandy soils, highly fractured rock or by having relatively high water tables. B. Task G-2 Objective; To define and map predominant agricultural acti- vities practiced in the vulnerable areas identified in Task G- 1. Scope; Agricultural activities on the land determine the nature and extent of possible groundwater contamination. The range of activities in areas of productive aquifers with vulnerable edaphic and geologic characteristics will be iden- tified. Approach; A map of agricultural activity regions will be superimposed on the vulnerable areas map prepared in Task G-l. This will enable the crop producing and cattle feeding areas of the country to be related to groundwater supply and the regimes of pesticides and fertilizer applications and feedlot operations to be determined. C. Task G-3 Objective; Within the vulnerable areas, to compare available water quality data from productive aquifers with predicted values obtained from Tasks G-l and G-2. Scope; Groundwater quality data, while imcomplete, is avail- able from several sources. These data can be used as a bench- mark to measure the accuracy of the regimes used in Task G-2 for predicting groundwater contamination. Approach; A review of groundwater data quality files for areas in which intensive agriculture is practiced within the vulnerable areas is a priority project task. Data of this type is available through the U.S. Geological Survey (USGS), state Water Resource Research Centers, U.S. Bureau of Census, U.S. Department of Agriculture (USDA), U.S. Environmental Protection Agency (EPA), Soil Conservation Service (SCS), 69 ------- state Agricultural Extension Services, Land Grant College's agricultural research programs, and U.S. Army Corp of Engi- neers. These data will be compared to the effects of nitrates and fertilizers on groundwaters from known agricultural practices in the vulnerable areas, as calculated in the previous task. D. Task G-4 Objective; To determine whether or not "best" agricultural practices can be used to abate groundwater problems. Scope; Up-to-date scientific knowledge and procedures are used in the management of many farms, particularly those operated as large corporate entities. The effectiveness of those practices, in areas of groundwater contamination, will be evaluated and compared to the less structured procedures used by the individual farm operator. Approach; In each vulnerable area, an "economic" farm will be selected, if possible, and the procedures and extent of use and control of pesticides and nitrates on that farm deter- mined. The groundwater quality of these areas will then be compared to areas in which no "economic" farm is operated. Soil, water tables, and geologic characteristics will be taken into consideration in the subsequent evaluations. III. NITRATES A. Fertilizers 1. Task FR-1 Objective; To determine the degree to which nitrate contamination of groundwater is attributable to agri- cultural application of fertilizers. [It may be possible to estimate how much nitrate in groundwater derives directly from fertilizers and how much from plant decay, nitrogen fixation, animal wastes and septic systems by a technique* using isotopes of nitrogen which are indi- cators—to a degree—of the nature of the source.] *This technique has been developed at Washington University, St. Louis, Missouri. 70 ------- Scope; The areas of investigation are limited to those in which there is intensive farming and high rate of nitrate fertilizer application. Regions with deep aqui- fers and low recharge levels need not be considered. Aquifers which can yield more than 50 gallons of water per minute to public water supplies are of primary con- cern. Approach: It is recognized that nitrates usually per- colate into soils at a greater rate during the winter months when plant uptake of nitrogen ceases, plant decay adds nitrogen to the soil, and groundwater recharge rates tend to increase. When assessing groundwater quality data, the time of testing needs to be determined, if it is obtainable. Data should be collected preferably in winter or early spring. Areas of fractured rock overlain by a shallow soil mantle are areas of high hazard since nitrates readily pass through the porous fissures in such rocks as creviced dolomite, limestone and shale. Areas of high water table (only a few feet below the surface) are less hazardous to groundwater from the nitrate point of view because the soil is in an anaerobic state (deficient in oxygen) where denitrification (nit- rate may be converted to nitrogen gas) is promoted if carbonaceous material is present. Nitrates do not quickly mix with the deeper levels of groundwater under conditions of laminar flow, but nor- mally "ride on top" of the groundwater water layer for many months. In taking samples it is well to know if the sample was taken from the top of the aquifer. With data obtained from G-l, G-2 and G-3, the following tasks will be carried out: Task FR-1A. Prepare mappings of the agricultural areas of the country to show levels of nitrate above acceptable levels (choose several levels greater than 5 ppm, greater. than 10 ppm, greater than 20 ppm, greater than 45 ppm and greater than 100 ppm) for different years of testing so as to indicate visually the increased level of nitrate pollution where it exists. Task FR-1B. Correlate fertilizer application levels versus crop and tillage practices, climatic conditions and aquifer flow rate. This data will allow for 71 ------- estimation of nitrate concentration increases in the groundwater through the increase of fertilizer appli- cation rates. Other factors such as a change in the time of application, or the use of less soluble forms of nitrogen—such as urea—can then be studied as to their effect on nitrate leaching into groundwater. Task FR-1C. The effort to study groundwater recharge must include some estimate as to the degree of recharge from local streams and ponds which are either high or low in nitrate. Surface streams tend to recharge the aquifers (and the aquifers recharge the streams). Often, during the late summer, the aquifer recharges the stream more than the stream recharges the aquifer. Nitrates from the top of the aquifer pass to the stream. In the winter the aqui- fer is recharged by the stream carrying nitrates and other soluble substances into the aquifer. A study of this balance will help to indicate the source of intrusion of toxic substances into the groundwater. 2. Task FR-2 Objective; To determine how farmers can control nitrate percolation into groundwater in those areas where ground- water nitrate problems have been traced to fertilizer applications. Scope; In each agricultural region there are some farms that are operated on a scientific and cost effective basis. Some of these farms are operated probably in areas experiencing groundwater nitrate toxification problems. It is in these areas, where fertilizer appli- cation is suspected of being the primary contributor to this groundwater problem, that farms should be selected for study. There should be strong similarity between each selected farm and the "control" farms in the area in topography and the crops grown. A number of farms should be selec- ted, with preferably two or three in each area studied. A selected pair of farms in one area may be as much as 20 to 50 miles apart. Approach; With data obtained from G-4, the tasks defined below will be pursued. In the event that this approach 72 ------- is successful, there will be a strong indication that an appropriate farm management training program would be bene- ficial. Also required will be effective research to determine the capacity of crops to take up nitrates (and other nut- rients) from fertilizers and soils. Fertilizer applications could then be made in optimum amounts and at judicious times so as to minimize the leaching and runoff potential. Task FR-2A. The first order of business is to set criteria and then to select and contact the farms to be used in the study. State or federal agricultural farms and previously studied farms can be included if they meet the criteria listed in the "Scope" above, but private operations will generally be chosen. Negotiations will determine the degree of cooperation (and the possible fee for the use of the farmer's time and facilities) which is required. It may be possible to in- corporate additional funding into the study from interested state agricultural agencies and extension services, and Water Resources Research Centers of the State, USDA Agricultural Research Service, USGS, soil conservation service, and land grant college agricultural programs. In some instances the use of equipment and personnel from these sources may sub- stitute for cash input to the study. For example, the state may provide the testing of water samples free. Task FR-2B. A file of the farm characteristics will be made, consisting of: (a) a topographical map of the farm which will also show locations of fences, buildings, wells, septic tanks, etc. (b) the history of the farm extending back at least 5 years, preferably 10 years or more, including all pertinent data that will help in determining what factors contributed to the local groundwater quality. These data include, but are not limited to the following: DATA OUTLINE o Cropping patterns and amounts planted o Yields o Fertilizer applications and types (include manner of application) o Pesticide usage 73 ------- o Tillage practices o Building additions and other physical changes to farm such as pond construction or creek dams, etc. (include timing information) o Livestock history o Climatic factors affecting crop o History of soils tests o History of any drilling of wells (test, drinking, irrigation) o Any practices which would affect groundwater (dump area for farm wastes, fertilizer and pesticide containers, etc.) o Septic tank and outhouse locations and periods of use (installed or stopped usage) o Other pertinent data such as water table levels, years when well was dry or low, etc. (c) test the present farm wells for nitrate levels and drill test wells at judicious locations about the pro- perty to obtain edaphic, geological, and hydrological characteristics of the farm. Lysimeters should be placed where appropriate. Nutrient and microbiotic matter in the soil, soil mois- ture, hydrologic conductivity, water quality in each of the wells placed on the property, etc. shall be recorded at least monthly. Precipitation, water runoff, tem- perature and humidity levels can be recorded automati- cally. The water runoff may be difficult to obtain due to topographical characteristics and may have to go unknown on some farms. Task FR-2C. Record the farm activities that take place during the year of study, including but not limited to the following: o Time of all activities o Record of pertinent weather conditions o Amounts of pertinent materials used 74 ------- o Tillage of various fields (plowing, disking, etc.) o Planting of seeds o Fertilizer applications o Irrigation water used o Changes in livestock patterns o Soils analyses o Crop yields o Pesticide applications o Cutting of hay, alfalfa, etc. o Changes in topographical features (e.g., new pond, or an old pond drained or serious erosion of an area) o Dumping on spillage of fertilizers and pesticides on the farm property o Dumping of wastes on the farm property o Any other significant operations Task FR-2D. Digest the data recorded and investigate for correlations between farming activities and the data developed on groundwater quality (nitrates and pesticide residues). B. Feedlots 1. Task FE-1 Objective; To establish a method of standardizing animal waste analysis and research reporting. Scope; Standardization will allow for a clear statement of any measurements or analysis techniques that may be required in future feedlot regulations as they apply to protecting groundwater from contamination (and as they apply also to runoff contamination). In order to compare research results and establish application rates there must be standardized data reporting. 75 ------- Approach: Data on location of research by climate and soil characteristics will be made. The depth of im- pervious layers, water tables, and other pertinent infor- mation will be reported. This is necessary in that future regulations may require analyses of the quality and quantity of minerals percolating through the soil as a result of feedlot operations. This approach can best be pursued by forming a team of experts in the field of animal wastes analysis and re- search. Using data provided from Task G-l, the team will carry out the following: Task FE-1A. Review the work previously accomplished in the areas of animal wastes analysis and research. Con- sideration must be given to the various conditions under which data must be collected and the purposes for which it is recorded. It is recommended that analyses be expressed on a dry weight basis, except possibly for liquids of low solids content (approximately 1% or lo- wer). There must be a procedure established whereby data taken in various locations and under extremely different cli- matological, edaphic, geological, and hydrological con- ditions can be related. The important point of the work is that the method of analysis and reporting be stan- dardized so that regulations can be written and enforced in a meaningful way. 2. Task FE-2. Objective; To assess the success of the various methods to control feedlot runoff and manures, particularly in relation to groundwater contamination. A secondary ob- jective is to develop a set of criteria for required sizes for waste storage facilities and for maximum feed- lot sizes and animal densities for specified control techniques used at sites in various regions of the nation. Scope; During the past five years or so techniques for collecting and holding feedlot runoff and manures have been adopted at many feedlot locations. The effective- ness of these techniques must be assessed. This project cannot be entirely segregated from efforts to prevent runoff of effluents into streams and ponds which also recharge groundwater. Approach: Investigate those feedlots which have been 76 ------- instrumented to determine the level of nitrate pene- tration into underlying soils, and ultimately into ground- water. Simultaneously select additional feedlots to be instrumented, which do not duplicate the above situat- ions, which use alternative collection and storage tech- niques. This selection is to be made to represent varied feedlot design, size, manure types, soil and climatic conditions, geology, and hydrology. Beef and dairy cattle, hog, and poultry feed operations will be con- sidered, with cattle operations receiving major emphasis. This approach will be best accomplished by performing the following tasks: Task FE-2A. Review available studies on projects which have analyzed certain feedlot designs for collecting and holding effluents and solids from feedlots. It is noted that many studies have been concerned primarily with preventing runoff into streams and ponds. Measurements of nitrate levels in nearby streams are usually avail- able. Many studies have identified the percolation of nitrates into the soil at points within the feedlot and about the perimeter. The most significant data are those from measurements made during the winter and spring seasons when nitrate concentrations usually appear higher. The review should be especially concerned with areas that include soils with shallow groundwater (15-50 feet) depth. Here nitrate concentrations in soils are im- portant because leaching into groundwater is potentially high. In humid zones the concentration of waste salts should be recorded and the degree of leaching determined. Where records exist on the quality of groundwater in the di- rection of flow away from the feedlot the dispersion pattern and amount of dilution should be calculated. Task FE-2B. In areas where feedlot operations are lo- cated on permeable soils overlying shallow aquifers, the groundwater contamination levels need to be investigated more extensively. The feedlots to be tested for ground- water contamination are to be those in regions repre- senting soil and manure types, geological, hydrological, and climatological conditions not covered by existing 77 ------- studies as identified in Task FI5-2A. Where feasible, when existing studies have incomplete data, efforts to test for the additional necessary data should be made at these sites. Tests should be conducted so as to obtain data which coincides with the standardization procedures being developed in Task FE-1. Since both tasks FE-1 and FE-2 will be in operation simultaneously, effective coope- ration will be needed between the two Task groups. The testing shall be performed around the feedlot pe- rimeter and at locations where the groundwater flows down stream of the feedlot. Existing wells should be utilized when feasible, but test wells should be installed as appropriate. Testing should be done at several intervals during the year to observe seasonal variations. Test wells should be drilled to a depth which will draw water samples from the upper levels of the aquifer. It is in this region that contaminants concentrate because of the minimal vertical mixing which occurs under con- ditions of laminar flow. Profiles of nitrate and salt concentrations in the soil should be obtained. Soil moisture, bio-oxygen demand (BOD), hydrological con- ductivity, and other parameters should be measured as required. In areas where the groundwater has not been contaminated, these data are invaluable in building a history for the feedlot region and feedlot design. Testing of the soils and groundwater should be coor- dinated with testing programs presently being conducted by the EPA's R. S. Kerr Laboratories (Ada, Oklahoma), Lhe U.S. Department of Agriculture, and the U.S. Geological Survey. Some of these programs involve in-house offoris and others are in connection with land grant schools and state water resource research programs. Task FE-2C. The task force will continually synthesize data and project the outlook for the future with respect to feedlot designs, manure types, edaphic, geological and hydrological conditions. This perspective will provide the context within which to develop the understanding required for the design of sound regulations for ground- water protection. 78 ------- 3. Task FE-3 Objective; To determine the degree of. groundwater tox L- fication resulting from recharge from animal waste ap- plications which are occasioned by feedlot operation. Scope; It is recognized that there are many means of disposing of animal wastes, including spreading, treat- ing, refeeding, synthesizing, burning and so forth. This task is concerned with the discharge of wastes on lands after various levels of treatment in holding and treating ponds. This study is most concerned with the effects on groundwater toxification as a function of application rates, edaphic characteristics, climate, geology, hy- drology and time of application. Approach; The following tasks will be carried out: Task FE-3A. A survey of areas where the application of animal wastes is affecting permeable soils with shallow groundwater (15-50 feet) will probably show that these conditions offer higher potential of groundwater con- tamination than areas that are arid. A survey of the nitrate levels in groundwater in these regions is re- quired, using files from local well testing data. This data will often mesh with the data collected in Task FE-2 and there should be a close working relation between the two task groups. Task FE-3B. Methods of application of animal wastes, as well as composition of the wastes, the amount and time of application, crop cover, climate, edaphic conditions and hydrology will be surveyed to determine which methods are applicable, and which are not, in identified regions and seasons. In Illinois, for example, nearly all recharge to ground- water occurs between the first of November and the end of April, during periods when evapotranspiration losses are minimal, soil moisture, deficiencies have been satisfied, and during periods when the ground is unfrozen. It would probably be inappropriate to apply animal wastes during this period, unless mitigating factors allow for winter applications. Plant capacities for nitrogen uptake, and the optimum 79 ------- times and rates of application, should be «ssesoed for the edaphlc conditions existing at various feedlot areas. Much of this data will have to be gathered from the land grant colleges, state agricultural research services, extension services, and the USDA's Agricultural Research Service (Dr. Stanford, USDA, Beltsville). Minimal data is now available in this area. These factors should be identified for all areas where waste spreading is conducive to groundwater contami- nation. Task FE-3C. Use the findings of this study to formulate guidelines or rules for upper limits on manure spreading in feedlot regions under specified conditions. C. Septic Systems and Groundwater 1. Task S-l Objective; To determine the extent of groundwater con- tamination that exists on farms as a result of septic tank use. Scope; The investigation will be limited to farms and will be further limited to areas representative of spe- cified soil conditions, geology, depth of water table, climate (precipitation available to dilute the waste water) and tank design. Approach: With data obtained from Task G-l, the fol- lowing activities will be pursued: Task S-1A. Since the density of septic tanks in farm areas is usually low (less than 10 units per square mile) the pollution potential for serious regional groundwater contamination probably does not exist, but local problems do occur. A set of areas around the country will be selected for which well test records are available. The areas are to be defined and segregated by soil types and geology. In cases where well contaminations occur at a statistically significant level, investigations will be extended to determine the pollution source. When septic sources are suspected, a study of well construction will be made and the corresponding septic tank history re- viewed. Poor design of either the well casing or 80 ------- positioning may be more at fault than the septic tank. Conversely, the septic design and construction may be inadequate. A determination of the facets of the problem will thus be made. Areas without high water tables will not be included, but areas with fractured porous rock below a thin soil cover should be investigated, even with only moderately high water tables. It is suggested that this study of farm septic tank pollution be made as a subset of a national study by the EPA Office of Air and Waste Management in their Solid Waste Management Program and that coordination be ar- ranged with the R. S. Kerr Experimental Research Labo- ratory (Ada, Oklahoma), where a long term septic tank study is already underway. It is anticipated from preliminary reviews that farm septic systems are an insignificant source of groundwater pollution, except on a local basis, in relation to the other sources of potential groundwater pollution from agriculture practices. Septic systems are too sparsely situated in a farm setting to be a major source of nit- rate contamination of groundwater. The only farming areas where a potential for widespread groundwater contamination may exist is where a farm or ranch supplies a concentrated area of housing for ranch and farm hands, and septic systems process the human wastes. This also applies to areas where migrant worker camps service substantial numbers of people in concent- rated pockets of farmland. IV. PESTICIDES A. Task P-l Objective; To determine the potential severity of toxifica- tion of groundwater that is suited to use for public drinking water supplies based on the history of past applications and the projected use of pesticides in the near future. Scope: Since groundwater contamination by pesticides and herbicides has been reported in only a limited number of instances it will be necessary that the records of Water Resource Research Centers in each state be reviewed. .Only those states and areas with intensive farming on permeable soil (sandy soil or thin permeable soil mantle over layered 81 ------- fractured rock, e.g., limestone,) with high water table and slow moving groundwater, need to be considered. Also, only those areas in which persistent varieties of pesti- cides are used would require such study. A minimum level of CH (chlorinated hydrocarbon - a per- sistent class of pesticides) pesticide concentration in groundwater would be set for the investigation. Only in areas where the minimum CH levels are surpassed will records of lower levels be investigated; this is to identify trend patterns. Approach; With data obtained from Task G-l, the fol- lowing will be carried out: Task P-1A. The task force formed to investigate this problem will review the records of CH usage in agri- culture. These data have been published by and in the files of the USDA, Agricultural Experimental Stations and Agricultural Extension Services. Only those data need to be researched which lie within areas of intensive farm- ing, very permeable soils (sand soils), high water table, and slow moving groundwater. Also, areas where the soil mantle is thin and is underlain by a fractured rock matrix, such as limestone, shale, etc. are candidate areas. The soil, geological, and hydrological data is provided by the Soil conservation Service of the USDA, U.S. Geological Survey, and state Geological Surveys. The areas to be investigated are those where a high water table is actually used for drinking water supplies. Task P-1B. With or without a formal groundwater mode!2 the data made available from the files of the various state agencies identified above will be used to determine the past, present and future migrations of CH residues. The future migrations will have to be (a) based on recent (last two years) application rates of CH; (b) based on the projected reduced rates because of present and pend- ing regulations; and (c) based on possible increased applications rates if warranted. Task P-1C. In areas where contamination of groundwater is known to exist, arrangements will be made for ob- taining a new and representative set of groundwater samples using the methodology and procedures described by the Association of Official and Analytical Chemists (AOAC). 82 ------- V. ECONOMIC IMPACT OF MEASURES TAKEN TO REMEDY GROUNDWATER CONTAMINATION A. Introduction and Overview This section will present a possible approach for assessing the economic impact of the measures taken to remedy groundwater contamination problems. It consists of a flow diagram of the complete procedure, a set of three objectives and a list of specific tasks necessary to meet the objectives. The economic impact portion of the plan of work would be undertaken whenever a groundwater contamination problem is discovered and defined. It would begin immediately after standards, guidelines or other remedies had been established to guarantee the future purity or safety of the groundwater; the benefits* of these remedies are expected to exceed the costs of enacting them. The economic impact analysis would determine the costs of the abatement more precisely and would allow a second posteriori assessment of the benefit assump- tion. The economic impact analysis will concentrateon the primary cost impacts and on the significant secondary impacts** as- sociated with the abatement of groundwater contamination. Primary impacts are changes in the output, costs or returns of firms or individuals whose operations would be directly affected by the standards, guidelines or remedies. Secondary impacts are the changes in prices, costs or quantities of goods occurring in the support industries, competing indus- tries or at the retail level. An example of a support in- dustry is the fertilizer industry. An example of a competing industry is the grassfed beef industry which would probably feel the impact of any feedlot regulations. Of course, we are all affected by higher retail prices and by shortages. *These benefits are primarily increases in the safety and health of current and future generations of human beings, of other animals, and of plants. **It should be noted that not all secondary impacts are costs. An increase in the cost to one firm or an industry may benefit a competing firm or industry. 83 ------- The procedure to be used in the economic impact analysis can be structured according to three main objectives. These are: (a) to choose the best set of possible alternative remedies to groundwater problems, (b) to determine the primary impacts of these alternative remedies on a firm, industry and regional basis, and (c) to identify and assess the significant secon- dary impacts of the most promising remedies. Inferior re- medies will be discarded at the completion of each phase of the analysis. This will keep the procedure efficient. On the other hand, the effort made to explore alternative methods of abatement under the first objective will help insure that the most rational remedies are subjected to the impact analysis. The three objectives are represented in the flow chart of the procedure (Figure 2-V-l) as three columns. In the lefthand column are the tasks to be performed in choosing the best abatement methods. As can be noted from the diagram, either a task-force approach or a Delphi technique can be used to complete this objective. In the middle column, the tasks necessary to assess the primary impacts are shown. Firm-level output and cost impacts would be determined while meeting the initial objective; hence, the tasks needed to complete the second objective are mostly concerned with aggregation to the industry and regional levels. The right-hand column and the third objective are concerned with delineating the major secondary impacts. Tasks required to fulfill this final objective are identification of impacts important enough to be analyzed; choice of analytical technique to use in the anal- ysis; and performance of the analysis itself. Two other aspects of the flow-charted procedure should be noted. An option to bypass Objective 1 is included to account for a situation where the standard, guideline or remedy is already known and/or specified by law. This option is not under any of the three objectives. Also noteworthy is the branch in the left-hand column which indicates that if a byproduct can be found from an abatement remedy which will pay for the remedy, then no further study of impacts is needed. An example of the first option might be a pesticide ground- water pollutant for which there is a substitute pesticide. Objective 1 can be bypassed if there is confidence that the one pesticide will be substituted for the other. An example of the second option would be a manure byproduct that makes it feasible to capture the liquid and solid wastes before they penetrate the soil surface. 84 ------- DBJECTIV! 1 Determine Remedies Primary Impacts Secondary Impacts Input: Description of Contamination, Acceptable Standards & Affected Firms Choose Remedies or Method of Evaluating Remedies Choose Experts (Delphi Technique) or Form Task Force Define Current Production Regions Remedy is Known Survey for or Calculate Technical and Economic Parameters Determine Number, Type & Size of Affected Firms I Choose I I Best Remedies t I I L , 1 Use Firm Parameters to Calculate Primary Impacts Delineate Major Secondary Impacts Select Economic Technique to Assess Secondary Impacts Compute Secondary Impacts Using Selected Technique 1 I Exit if I Primary Impacts I Negligible L Summarize Impacts & Exit I Exit if I Remedy Covers Cost J Figure 2-V-l Flow Diagram of Economic Impact Analysis 85 ------- B. Task E-l: Choose Alternative Remedies Objective; The goal here is to determine the most technically and economically feasible ways of abating groundwater con- tamination. In many cases, the most feasible abatement al- ternative may be well known and/or well documented in the literature. For example, it may be well known that one pes- ticide will readily substitute for another and that this substitution will relieve the need for major changes in current agricultural production practices. Objective 1 would be bypassed in this case. A case in which Objective 1 would not be bypassed might be a feedlot waste disposal problem where the remedies could range from building an effluent and solid waste holding system to manufacturing a byproduct such as composted manure or methane gas. In such a case, feasible alternatives have to be defined and their technical and econo- mic parameters determined before the remedies most likely to be used can be chosen. Scope; Limited to those specific contamination problems where several attractive abatement alternatives exist and where choice of the most feasible remedy is not easily made. Approach; Either a Delphi procedure or a Task Force approach will be used. The Delphi approach will be preferred for the easier choice problems. The more complicated Task Force approach would be used if the choice problem is difficult. Task E-1A. Choose analytical method to be used in determining most feasible contamination remedies. To do this, one would (a) assemble information about scope, seriousness and attri- butes of groundwater contamination problem (from earlier phases in project), (b) gather what easilyobtainable infor- mation about possible abatement procedures exists, and (c) in conference with EPA representatives, choose either the Delphi technique, the Task Force approach or the most likely remedy- (ies). If a remedy, or a set of remedies, is chosen during completion of this task, the other tasks under Objective 1 would be omitted. Task E-1B. Choose experts to be polled in Delphi technique or choose members of task force. Experts for the Delphi procedure would come from both inside and outside government and would be knowledgeable about both the technical and the business aspects of the agricultural firms contributing to the groundwater contamination. The group should include some representatives of the firms which would be affected by the abatement practices. If a task force is formed it should 86 ------- include Agricultural Scientists (who would know about plant varieties, row spacings, cultivation practices, etc.)> Agri- cultural and/or Civil Engineers (who would know equipment and processes), and Agricultural Economists (who would know mar- kets and comparative costing techniques). Such a task force could use a systems approach in studying the alternative abatement possibilities. The credibility of this approach is attested to by such successes as the development of mechanical harvesting for tomatoes. Task E-1C. Perform analyses needed to make choice of abate- ment alternatives and calculate cost and returns of each alternative remedy. These analyses need to generate two kinds of information: technical parameters and economic parameters. In the final rounds of the Delphi procedure, if it were used, experts would be polled about such items as fertilizer appli- cation rates, recommended varieties, sizes of holding ponds, equipment needed for methane gas production, costs of appli- cation, equipment, etc. and prices of composted manure, etc. These questions would be formulated for only a few of the most promising remedies and only near the completion of the Delphi procedure; otherwise, the response rate of the experts will be inadequate. If a task force approach is used, the member of the force who has the relevant expertise will take final responsibility for providing each relevant parameter. Since cost and price parameters are included, one output of this task will be the direct impacts of the pollution abatement on the affected firms. If this task is not performed, the direct economic impacts of the known remedy would be calculated as part of Task E-2C. Final Note; A task Force analysis might turn up a byproduct process which will abate the groundwater pollution and pay for itself while doing so. Objectives 2 and 3 would be omitted in this case as additional cost impacts would be well outweighed by the benefits accruing from the pollution abatement. C. Task E-2: Determine Primary Industry Effects Objective: Cost and/or output impacts on the industries containing the polluting firms are to be determined during the. completion of this objective. Also, if the cost impacts directly associated with polluting firms were not calculated under Objective 1, they will be determined here. Industry impacts are of critical importance in order to assess the national and international trade effects of the abatement remedies. If these are negligible, costs of abatement will 87 ------- be borne primarily by the polluters. If they are significant, abatement will also include social costs. Since these costs may vary by region, a regional stratification will be made. If primary impacts at the industry level are negligible, Objective 3 can be omitted. Scope; Attention will be focused only on U.S. agricultural production industries directly affected by corrective action. The impacts of remedial action upon supportive and competitive industries or on final consumers will be determined in Objec- tive 3. Approach; The impact of corrective action will be determined via collection and revision of existing USDA and Bureau of the Census data. Task E-2A. Define Current Production Regions. Efforts to determine the regional distribution of production should be closely coordinated with executors of the technical and engi- neering phases of the total analysis. It will be necessary to arrive jointly at relevant regional definitions. Soil types, and location of major market areas and supportive industries should be considered. Regional delineation is of critical importance because the imposition of corrective measures could alter significantly the nature of competition that exists between major production areas. Task E-2B. Determine number and size distribution of firms affected in each region. It is possible that remedial action will affect only small firms in one region. If the region is characterized by a wide range of firm sizes, the effects of corrective action in all probability will be small. However, if the instituted action affects a large firm which accounts for a large share of regional and national output, the econo- mic impact could be rather significant. Therefore, to arrive at a realistic assessment of the primary effects it will be necessary to consult USDA and Bureau of the Census data. These data and associated studies will be used to derive size distributions of firms by region. Task E-2C. Use firm parameters to calculate total impact on industry by region. Given the isolation of areas where cor- rective action is necessary (output technical and engineering phase) and firm parameters developed under Objective 1 of the economic impact analysis, the total impact on the industry will be calculated by region. Changes in firm cost structure reported under Objective 1 will be translated into industry 88 ------- and regional price and quantity changes. If the cost impacts on the affected firms have not been calculated previously, they will be computed as part of this task. Partial budgeting procedures will be used to carry out this computation. D. Task E-3. Determine Secondary Effects Objective; The purpose of this objective is the quantifica- tion of the effects remedial action has on supportive and competitive industries. Demand for outputs and/or services rendered by industries serving in support roles, such as the feed grain industry in the case of feedlots, could be severely altered by the institution of corrective measures. Competing industries, such as the grass-fed beef industry once again in the case of feedlots, may find the demand for their products increased as a result of government intervention. An addi- tional possible outgrowth of the correction of spillover activities is the increase in prices at the consumer level. The nature of the effect on consumers, as well as the pre- viously mentioned secondary impacts, will be derived using the results generated under Objectives 1 and 2. Scope; The analysis will be limited only to supportive and comparative industries indicated to be affected by results derived under Objectives 1 and 2. Consumer impacts will be determined only in situations where significant price changes are indicated. Approach; Examination of results of tasks accomplished under Objectives 1 and 2 to determine impact areas. Select appro- priate economic tools and execute the analysis. Task E-3A. Delineate major impacts which should be studied. Assessment of secondary impacts will require identification of affected supportive and competitive industries. Findings under Objectives 1 and 2 will set the initial boundaries. For example, evidence discovered in the execution of tasks con- tained in Objective 2 may indicate a decrease in the demand for feed grains as a result of feedlot regulation. Given this information, the analysis can proceed to the determination of the feedgrains affected. Results obtained under Objectives 1 and 2 will be used also in the assessment of the effects remedial action will have upon consumers. Task E-3B. Selection of Economic Tools. Several possible economic tools are available which can be used to perform 89 ------- an impact analysis. Budgeting aggregation, commodity section models, input-output analysis, and economic base analysis are examples of possible techniques which could be used to deter- mine the impact of remedial action on supportive and competi- tive industries. The final decision as to the technique used will be based on output generated under Objectives 1 and 2, in consultation with informed industry, EPA representatives and other quali- fied sources. Consumer impacts will be derived via the use of the price elasticity of transmission and Griliches' social welfare approach. Task E-3C. Execution of Analysis. Once the boundaries for the analysis have been established and tools selected, it will be necessary only to collect the relevant data and to locate the necessary parameters and proceed with the chosen analy- tical procedure. VI. MODELING A. Task M-l Objective; The objectives of modeling a particular situation such as the intrusion of toxic substances into groundwater recharge, whether from nitrates or pesticides, is to be able to predict on a fairly reliable basis what the future conse- quences will be with continued use of these substances. Modeling should also permit us to vary certain parameters so as to determine the application level at which the substance would no longer toxify the groundwater. It is desired that modeling be capable of dealing with large land areas in order to describe adequately the expected effect on an aquifer for several years in advance. Scope; At present the state-of-the-art in groundwater model- ing does not permit the modeling of large areas. It will be necessary therefore to determine the extent to which various existing models can be adapted to this purpose, and the degree of reliable prediction to be expected and the number of input parameters required. The task will be to select a model or to adapt a set of models and suitable submodels which can fulfill the objective of this program. Modeling of a sophisticated nature is not warranted for areas showing small changes of nitrate in groundwater over a period of a decade or more since fertilizer and animal waste applications obviously do not add significantly to these groundwater contaminations. 90 ------- Approach; The objectives of the program will be reached by the accomplishment of the following tasks: Task M-1A. During June of 1975 the EPA awarded a contract to the Commission on Stimulation Modeling of the Scientific Committee on Problems of the Environment to evaluate the existing groundwater basin management models (EPA project control number R803713-01). A liaison with this committee should be established by the EPA groups concerned with model- ing the effects of fertilizers, pesticides, feedlots, and septic tanks on groundwater recharge. Even though the commit- tee's work is scheduled for completion in July 1976, the modeling groups will receive invaluable benefit from the collected ideas and will also be able to share their insights. Among the above group of individuals interacting with the Committee the EPA should assign a team of persons who-will be responsible for developing a groundwater model. Task M-1B. (a) Using the findings of the Scientific Committee on Problems of the Environment, a modeling effort for fertili- zers can develop a non-point source model to predict the quantity of groundwater which will be toxified by applications of fertilizer under various assumptions. The initial phase of this Task will be to develop a working model which will pre- dict the effects on groundwater from various levels of ferti- lizer applications versus suitable parameters within a water- shed or basin. This will be utilized to determine the time period in which toxification will occur (if indeed it will). It will also be an aid to agricultural extension services around the country in recommending fertilizer application rates so as to protect groundwater recharge. Task M-1B would be designed to model a watershed or basin using available data from well tests. The well data will have to span at least a decade or more and be correlated to ferti- lizer application levels (along with crop practices, clima- tology, hydrology, etc.) of the affected area. The modeling effort will be designed to produce a simplified model which will take into consideration the change in fertilizer appli- cation patterns over the years and relate them to the changes in the nitrate levels in the groundwater (as recorded from well test sample taken over the last decade). Once an histo- rical pattern is determined, fertilizer application levels should be simulated which show how the groundwater nitrate level can be influenced by fertilizing at versus other 91 ------- relevant factors including changes of crop or tillage prac- tices. The data for Task M-1B will be supplied through the efforts of the Fertilizer Task group determining the extent of nitrate toxification of groundwater as resulting from fertilizer usage. (b) Part 2 of Task M-1B is the same as Part 1, except that it would be applied to pesticides using data supplied by the Pesticide Task group. Task M-1C. In that the EPA, Athens, Georgia, laboratory is already concerned with modeling the effects of pesticide in sub-surface and surface run-off situations, and are funding an approximately 20 square mile test area to calibrate the model, it would be reasonable to extend the program by means of additional funding to include the effects of pesticides on underground recharge areas in addition to those of subsurface run-off aquifers, (i.e., those aquifers which intersect a surface water body such as a river or lake.) Only a modest increment in funds would be required to develop a subprogram to handle the case in hand. Task M-1C would be a more detailed effort that Task M-1B and would demand more specific data to be taken and cover a less extensive area than Task M-1C. Task M-1D. An effort to model point sources of nitrate in- trusion into soils, (i.e., from feedlots, barnyards, dairy cow milking areas, poultry houses, and septic tank operation) should be attempted using models developed by ERDA, which already account for various ground factors and chemical chan- ges. This modeling group can be the same group as described in Modeling Task M-1B; if a different group, it should operate in a manner similar to that of modeling Task M-1B. The model should include operation of the point source during the start- up period, normal operation period, and phase-out period. The model should predict what limits are to be set on size, dis- tance from the aquifer and/or wells, and the conditions of operation of the point source, in order to preserve the quali- ty of the underground waters. Note on Modeling Task; Modeling is not a problem in itself but a tool for analysis. The sophistication of the model should be of the same order of magnitude as the precision of the data which will be available as input to the model. 92 ------- THE IMPACT OF INTENSIVE APPLICATION OF PESTICIDES AND FERTILIZERS ON UNDERGROUND WATER RECHARGE AREAS WHICH MAY CONTRIBUTE TO DRINKING WATER SUPPLIES Section 3 Bibliography 1. Aldrich, S.R., Determining Application Rates of Livestock Wastes to the Land, Livestock Waste Management Conference, 1973. 2. . Plant Nutrients, Illinois Pollution Control Board, 1972. 3. Allison, F.E., "Nitrogen and Soil Fertility, "U.S. Yearbook of Agriculture, pp. 86, 1957. 4. Brady, N.C., The Nature and Properties of Soils, MacMillan Publishing Company Inc., Newark 8th Edition, 1974. 5. Bredehoeft, J.D., Finder, G.F., Application of Transport Equations to Groundwater Systems, Underground Waste Management and Environmental Implications Proceedings of a Symposium held jointly by the USGS and the American Association of Petroleum Geologists, pp. 191, 1972. 6. . "Mass Transport in Flowing Groundwater," Water Resources Research, Volume 9, Number 1, pp. 194, 1973. 7. Brezonik, P.L. and Lee, G.F., "Denitrification as a Nitrogen Wink in Lake Mendota, Wisconsin," Environmental Science and Technology, 1968. 8. Butchbaker et al, Evaluation of Beef Cattle Feedlot Waste Management Alternatives, EPA, 1971. 9. Case, A.A., The Health Effects of Nitrate in Water, Proceedings of the 12th Sanitary Engineering Conference, University of Illinois, 1970. 10. Commoner, B., The Killing of a great Lake, World Book Year Book, 1968. 93 ------- 11. Corey, R.B. et al, Excessive Water Fertilization, Report to the Water Subcommittee of State Agencies, 1967. 12. Crawford, N.H. and Donigian, A.S., Pesticide Transport and Runoff Model for Agricultural Lands, EPA, Office of Research and Development, 1973. 13. Crosby, J.W. Ill, Johnstone, D.L., Drake, C.E., and Fenton, R.L., "Migration of Pollutants in a Glacial Outwash Environment," Water Resources Research, Volume 4, Number 5, 1968. 14. Davidson, J.M. et al, Use of Soil Parameters for Describing Pesticide Movement Through Soils, EPA, National Environmental Research Center, 1975. • 15. Doneen, L.D., Effects of Soil Salinity and Nitrates on the Drainage in San Joanquin Valley, California, Water Sciences and Engineering, paper 4002. 16. Duguid and Reeves, Material Transport Through Porous Media: A Finite-Element Galerkin Model, Oak Ridge National Laboratory, ERDA, 1975. 17. EcoSystems, Incorporated, A Manual for Executing Short-Run Studies on the Economic Impact of the Restriction of Carbaryl or Other Insecticides, 1975. 18. Eliassen, R. and Techobanoglous, G., Removal of Nitrogen and Phosphorous from Waste Water, Environmental Science and Technology, 1969. 19. Engberg, Richard A., The Nitrate Hazard in Well Water With Special Reference to Holt County, Nebraska, USGS Professional Papers, 1967. 20. Erwin, B. and Waterworth, A., Nitrogen Cycle in Surface and Subsurface Waters, EPA, Office of Research and Monitoring, 1973. 21. Eye, J.D., Aqueous Transport of Dieldrin Residues in Soils, J. Water Poll. Contr. Fed., 40(8), Pt. 2, pp. 316-331, 1968. 22. Faye, R.E., Mathematical Model of the San Juan Valley Groundwater Basin, San Benito County, California, USGS, 1974. 23. Federal Working Group on Pest Management. Guidelines on Sampling and Statistical Methodologies for Ambient Pesticides Moni- toring, October 1974. 94 ------- 24. Frere, M.H., "Adsorption and Transport of Agricultural Chemicals in Watersheds," Transactions of the American Society of Agricultural Engineers, Volume 16, Number 3, 1973. 25. Frere, M.H., Onstad, C.A. and Holtan, H.N., ACTMO: An Agricultural Chemical Transport Model, Agricultural Research Service, USDA, 1975. 26. Fuhriman and Barton, Groundwater Pollution in Arizona, California, Nevada and Utah, EPA, 1971. 27. Garner and Smith, The Disposal of Cattle Feedlot Wastes by Pyrolysis, EPA, 1973. 28. Green, R.E.,.Pesticide Mobility and Degradation in Soil-Waste Systems, University of Hawaii, 1974. 29. Griliches, A., "Research Costs and Social Returns: Hybrid Corn and Related Innovations," Journal of Political Economics, 66:419-431. 30. Hargett, N.L., Fertilizer Summary Data, National Fertilizer Development Center, 1974. 31. Harmeson, R.H. and Larson, T.E., Interim Report on the Presence of Nitrates in Illinois Surface Waters, Proc. 111. Fertilizer Conf., 111. Fertilizer Ind. Assoc., Champaign, 111. pp. 33, 1969. 32. Harshbarger, et al, Arizona Water, USGS, 1966. 33. Hirsch, P., Overein, L. and Alexander, M., Formation of Nitrite and Nitrite by Actinomycetes and Fungi, J. Bacteriol. 82:442-448. 34. Hutchison, G.L. and Viets, F.G., Jr., "Nitrogen Enrichment of Surface Water by Absorption of Ammonia Volatilized from Cattle Feedlots," Science, Number 166, pp. 514-515, 1969. 35. Ingols, R.S. and Navarre, A.T., "Polluted Water from the Leaching of Igneous Rock," Science, Number 116, pp. 595-596, 1952. 36. James, L., and Lee, R.E., Economics of Water Resources Planning, McGraw-Hill Book Company, New York, pp. 615, 1971. 37. Karubian, J.F., Polluted Groundwater: Estimating the Effects of Man's Activities, EPA, National Environmental Research Center, Las Vegas, Nevada, 1974. 95 ------- 38. Keeley, J.W., and Sealf, M.R., "Aquifer Storage Determination by Radiotracer Techniques," Groundwater, Volume 7, Number 1, 1969. 39. Kohl, D.H., Shearer, G.B. and Commoner, B., "Fertilizer Nitrogen: Contribution to Nitrate in Surface Water in a Corn Belt Watershed," Science, Number 174, pp. 1331-1334, 1971. 40. Krause, H.H. and Batsh, W., "Movement in Fall-Applied Nitrogen in Sandy Soil," Can. J. Soil Science, Number 48, pp. 363-365, 1968. 41. Lagerwerff, J.V., Heavy Metal Contamination of Soils, USDA, 1966. 42. Lehr, et al, Proceedings of the Second National Groundwater Quality Symposium, EPA, 1974. 43. Lijinsky, W., and Epstein, S., "Nitrosamines as Environmental Carcinogens," Nature, 225, 21, 1970. 44. Lorimor, J.C. et al, "Nitrate Concentrations in Groundwater Beneath A Beef Cattle Feedlot," Water Resources Bulletin, Volume 8, Number 5, 1972. 45. Mansfield, G.R. and Boardman, Leona, "Nitrate Deposits in the United States," U. S. Geological Survey Bulletin, Number 838, 1932. 46. Marshall, K.C. and Alexander, M., Nitrification by Aspergillus Flavus, J. Bacteriol, Number 83, pp. 572-578, 1962. 47. McCoy, E., Nitrogen Cycle in Surface and Subsurface Waters, Tech. Compl., Rep. OWRR B-004-Wis., pp. 30-42, 1968. 48. Mishan, E.J., Economics for Social Decisions; Elements of Cost- Benefit Analysis, Praeger Publishers, New York, pp. 151, 1973. 49. Murphy, L.S. and Gosch, J.W., Nitrate Accumulation in Kansas Groundwater, Proj. Compl. Rep. Kan. Water Resources Res. Ins., Kan. State University, Manhattan, Kansas, 1970. 50. National Academy of Sciences, Accumulation of Nitrate, pp. 106, 1972. 51. National Research, Council, "Agricultural Soil Maps," Highway Research Board, 1957. 52. National Science Foundation, Executive Summary and Continuation Proposal for Study of Certain Ecological and Economic Consequences of the Use of Inorganic Nitrogen Fertilizer, 1974. 96 ------- 53. Papadopulos and Winograd, Storage of Low-Level Radioactive Wastes in the Ground: Hydrogeologic and Hydrochemical Factors, EPA, 1974. 54. Pauszek, F.H., Digest of the 1972 Catalog of Information on Water Data, USGS Water Resources Investigations Number 63-73, 1973. 55. Pinder, G.F., "A Galerkin-Finite Element Simulation of Groundwater Contamination on Long Island, New York," Water Resources Research, Volume 9, Number 6, pp. 1657-1669, December 1973. 56. Porter, L.K. and Beard, W.E., "Retention and Volatilization of Lindane and DDT in the Presence of Organic Colloids Isolated from Soils and Leonardite," Agricultural and Food Chemistry, Volume 16, Number 2, pp. 344, March/April, 1968. 57. Proctor, D.E., Amounts, Composition, Characteristics and Pollutional Properties of Animal Wastes, Proceedings of the Pacific Northwest Animal Industry Waste Conference, 1964. 58. Reeves and Duguid, Water Movement Through Saturated-Unsaturated Porous Media: A Finite-Element Galerkin Model, AEG, Oak Ridge National Laboratory, 1975. 59. Robbins, J.W.D. and Kriz, G.J., "Groundwater Pollution By Agriculture," Groundwater Pollution, 1973. 60. Robertson, J.B., Digital Modeling of Radioactive and Chemical Waste Transport in the Snake River Plain Aquifer at the National Reactor Testing Station, Idaho, USGS, 1974. 61. Robson, S.G., Feasibility of Digital Water-Quality Modeling Illustrated By Application at Barstow, California, USGS, 1973. 62. Scalf, M.R. et al, Fate of DDT and Nitrate in Groundwater, Robert S. Kerr Water Research Center, ADA, Oklahoma, 1968. 63. Schmitz and Seckler, "Mechanized Agriculture and Social Welfare: The Case of the Tomato Harvester," Journal of Agricultural Economics. Volume 52, Number 4, pp. 569-577, 1970. 64. Scientific Committee on Problems of the Environment, Evaluation of Existing Groundwater Basin Management Models, to be published in 1976. 65. Shuyler, L., National Animal Feedlot Wastes Research Program, EPA, 1973. 97 ------- 66. Smith, G.E., Nitrate Problems in Plants and Water Supplies in Missouri, Mo. Agr. Exp. Sta., Columbia, Mo., 1965. 67. Soils Science Society of America, Symposium on Pesticides and Their Effects on Soils and Water, ASA Special Publication Number 8, 1966. 68. Spencer, W.F., "Distribution of Pesticides Between Soil, Water and Air," Pesticides in the Soil; Ecology, Degradation and Movement, 1970. 69. Stanford, George, Development and Utilization of Improved Methods for Predicting Nitrogen Fertilizer Needs in Agriculture: A Preliminary RANN-NSF Proposal, 1975. 70. Stanford, George, Epstein, Eliot, "Nitrogen Mineralization-Water Relations in Soils," Soil Science Society of America Proceedings, Volume 38, Number 1, pp. 103, 1974. 71. Starkey, R.L., Interrelationships Between Microorganisms and Plant Roots in the Rhizosphere, Bacteriol. Rev., 22:154-176, 1958. 72. Stewart, B.A. et al, Distribution of Nitrates and Other Water Pollutants Under Fields and Corrals in the Moddle South Platte Valley of Colorado, U.S. Department of Agriculture, 1967. 73. Taylor, C.R., Swanson, E.R., Economic Impact of Imposing Per Acre Restrictions on Use of Nitrogen Fertilizer in Illinois, Illinois Agricultural Economics, 1974. 74. Thomas, H.E., "Groundwater Regions of the U.S. - The Storage Facilities," The Physical and Economic Foundation of Natural Resources, Volume 3, 1952. 75. Thomson, T.L., The Occurrence of Nitrifying Microorganisms in Aquatic Environment, University of Wisconsin, 1966. 76. Tiebout, C.M., The Community Economic Base Study, Committee for Economic Development, 1962. 77. U. S. Department of Agriculture. Cattle Feeding in the U. S., Economic Research Service, 1970. 78. . "Commercial Fertilizers," Statistical Reporting Service, Bulletin Number 472, 1971. 79. . Commercial Fertilizers: Consumption in the U. S. FY 1974, Statistical Reporting Service, 1975. 98 ------- 80. . Cropping Practices: Corn, Cotton, Soybeans and Wheat 1964-70, Statistical Reporting Service. 81. Quantities of Pesticides Used by Farmers in 1966, Economic Research Service, Agricultural Economic Report Number 179, 1970. 82. U. S. Department of Commerce, "A Multiregional Input-Output Model for the United States," Economic Development Administration, 1970. 83. . Detailed Housing Chatacteristics, Bureau of the Census, 53 Volumes, 1970. 84. U. S. Department of Commerce, Groundwater Pollution, Part 2: Pollution from Irrigation and Fertilization, A Bibliography with Abstracts, National Technical Information Service, 1975. 85. U. S. Environmental Protection Agency, Abbreviated List of Publications and Guideline Documents Dealing with Monitoring Quality Insurance, Office of Monitoring Systems, 1974. 86. . Groundwater Contamination in the Northeast States, Office of Research and Development, June 1974. 87. . The Movement and Impact of Pesticides Used for Vector Control on the Aquatic Environment in the Northeastern U. S., Office of Water Programs, 1972. 88. . The National Groundwater Quality Symposium. 89. . On Site Domestic Waste Disposal, Office of Air and Waste Management, June 1975. 90. U.S. Geological Survey, Catalog of Information On Water Data, Volumes 1-19, Office of Water Data Coordination, 1973. 91. . Distribution of Principal Kinds of Soils: Orders, Suborders, and Great Groups (map), 1967. 92. . Geology (map), 1966. 93. U. S. Public Health Service, U. S. Public Health Service Chemical " Standards of Drinking Water, 1962. 94. U. S. Water Resources Council, Essentials of Groundwater Hydrology Pertinent to Water Resource Planning, Hydrology Committee, 1973. 99 ------- 95. VanderLeeden, F., Cerrillo, L.A., and Miller, D.W.^ Groundwater Pollution Problems in the Northwestern United States, EPA, Office of Research and Development, 1974. 96. Versar Inc., "Identification of Organic Compounds in Effluents from Industrial Sources," April 1975, for Office of Toxic Substances, EPA. 97. Viets, F.G. and Hageman, R.H., "Factors Affecting the Accumulation of Nitrate in Soil, Water and Plants," Agricultural Handbook,. Number 413, 1971. 98. Wadleigh, C.H., Wastes in Relation to Agriculture and Forestry, Agricultural Research Service, 1968. 99. Weber, J.B. et al, "Pesticides: How They Move and React in the Soil," Crops Soils, Volume 25, Number 1, pp. 14-17, 1972. 100. Private communication with Hend Gorchev, P.E., Ph.D. EPA Office of Research and Development, Washington, D.C. 101. Private communication with Dr. Yaron Sternberg, Engineering, Univ. of Maryland. 102. Private communication with Dr. Charles Helling, USDA, Agricultural Research Service, Beltsville, Md. 103. Private communication, Dr. H. P. Nicholson, EPA Southeast Environmental Research Laboratory, Athens, Georgia. 100 ------- TECHNICAL REPORT DATA (Please read Instructions on the reverse before completing) 1. REPORT NO. EPA 560/3-75-006 2. 3. RECIPIENT'S ACCESSION-NO. 4. TITLE AND SUBTITLE The Impact of Intensive Application of Pesticides and Fertilizers on Underground Water Recharge Areas Which May Contribute to Drinking Water Supplies 6. REPORT DATE December 11. 1975 6. PERFORMING ORGANIZATION CODE 7. AUTHOR(S) David Garrett, P.E., Francis P. Maxey, Herbert Katz 8. PERFORMING ORGANIZATION REPORT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS Special Projects Branch Office of Toxic Substances (WH-557) Washington, D.C. 20460 10. PROGRAM ELEMENT NO. N/A . 11. CONTRACT/GRANT NO. 12. SPONSORING AGENCY NAME AND ADDRESS U.S. Environmental Protection Agency Office of Toxic Substances Washington, D.C. 20460 13. TYPE OF REPORT AND PERIOD COVERED 14. SPONSORING AGENCY CODE 15. SUPPLEMENTARY NOTES 16. ABSTRACT A report was submitted on an assessment of the impact of intensive application of pesticides and fertilizers on underground water recharge areas which may contribute to drinking water supplies and also a plan for developing additional information required to define the nature and extent of the impact of agricultural practices on groundwater supplies for public water systems, as required by the Safe Drinking Water Act (PL-93- 523). Both the assessment and the plan were subsumed under the four headings of nitrates, pesticides, economic impacts, and modeling and simulation. Sources of groundwater pollutants were considered with a view towards determining thei relative contribution to the overall problem. Special emphasis was placed on feedlot operation, a source of significant concern. Fertilizers, pesticides, and septic tanks were also examined, along with a detail examination of the nitrogen cycle. Economic impact of changes in a&ronswie jp-raetices y&?p t.akfiji intp ac.c,ountj, and suggestions were nade concenuiisg; the 7. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS Pesticides in Groundwater Fertilizers in Groundwater Groundwater Pesticides in Drinking Water Fertilizers in Drinking Water Groundwater as Drinking Water Supply Nitrates in Groundwater Groundwater Nitrates in Drinking Water Vulnerability Phosphates in Drinking Water Modeling Ground- Phosphates in Groundwater water Feedlot Pollution of Ground- Contamination water Septic Tank Pollution of Groundwater 8. DISTRIBUTION STATEMENT Release Unlimited 19. SECURITY CLASS (This Report) Unclassified 20. SECURITY CLASS (Thispage) Unclassified 21. NO. OF PAGES 107 22. PRICE EPA Form 2220-1 (9-73) ------- INSTRUCTIONS 1. REPORT NUMBER Insert the EPA report number as it appears on the cover of the publication. 2*. LEAVE BLANK 3. RECIPIENTS ACCESSION NUMBER Reserved for use by each report recipient. 4. 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