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
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Document is available to the public through the National
Technical Information Service, Springfield, Virginia 22151.
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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
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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.
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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
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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 •
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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
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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
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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
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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.
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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.
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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].
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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
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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].
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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,
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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
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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
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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
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Figure 3.-II-1. ' • . •:•
Groundwater withdrawn, by regions, 1970 in, million gallons a day
10
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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
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. 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
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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
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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
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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.
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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.
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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.
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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
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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
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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,
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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
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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,
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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.
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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,
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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.
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00
FEEDLOTS
FERTILIZERS
GENERAL
PESTICIDES
SEPTIC TANKS
RECOMMENDED
MEASURES
FOR
CONTROL
Figure 2-1-1 Activity Streams
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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),
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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.
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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
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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
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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
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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
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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.
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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
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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
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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.
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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
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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
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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
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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).
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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.
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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.
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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
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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
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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
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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
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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
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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
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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
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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.
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THE IMPACT OF INTENSIVE
APPLICATION OF PESTICIDES
AND FERTILIZERS ON UNDERGROUND
WATER RECHARGE AREAS
WHICH MAY CONTRIBUTE TO
DRINKING WATER SUPPLIES
Section 3
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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
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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
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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)
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