EPA-600/4-76-036
July 1976
MONITORING GROUNDWATER QUALITY:
ILLUSTRATIVE EXAMPLES
Edited by
Richard M. Tinlin
General Electric CompanyTEMPO
Center for Advanced Studies
Santa Barbara, California 93101
Contract No. 68-01-0759
Project Officer
George B. Morgan
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
LAS VEGAS, NEVADA 89114
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This report has been reviewed by the Environmental Monitoring and Support Laboratory-
Las Vegas, U.S» Environmental Protection Agency, and approved for publication. Ap-
proval does not signify that the contents necessarily reflect the views and policies of the
U.S. Environmental Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use,,
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ABSTRACT
This report is designed to show by example site-specific procedures for
monitoring various classes of groundwater pollution sources. The first five
case histories of actual or potential groundwater pollution are presented
with the monitoring techniques which were employed as well as a retrospec-
tive view of these techniques and their efficacy. The case histories cover
brine disposal in Arkansas, plating waste contamination in Long Island,
New York, landfill leachate pollution in Milford, Connecticut, an oxidation
pond near Tucson, Arizona, and multiple-source nitrate pollution in the
Fresno-Clovis, California, metropolitan area. The report concludes with
hypothetical illustrative examples for developing and selecting monitoring
alternatives based on a cost comparison between other alternatives and
hydrologic judgment. The examples illustrated cover agricultural return
flow, septic tanks, percolation ponds, and landfills.
in
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ACKNOWLEDGMENTS
Dr. Richard M. Tinlin, Dr. Lome G. Everett, and the late Dr. Stephen
Enke of General ElectricTEMPO were responsible for management and
technical guidance of the project under which this report was prepared.
The following consultants made major technical contributions to this report:
Mr. James J. Geraghty and Mr. Nathaniel M. Perlmutter of Geraghty &
Miller, Inc. , Dr. David K. Todd, Berkeley, California, Dr. Kenneth D.
Schmidt, Fresno, California, Mr. John S. Fryberger of Engineering Enter-
prises, Inc., Norman, Oklahoma, and Dr. L. G. Wilson, Tucson, Arizona.
The following officials were responsible for administration and technical
guidance of the project for the U. S. Environmental Protection Agency:
Office of Research and Development (Program Area Management)
Mr. Albert C. Trakowski, Jr.
Mr. John D. Koutsandreas
Environmental Monitoring and Support Laboratory, Las Vegas
(Program Element Direction)
Mr. George B. Morgan
Mr. Edward A. Schuck
Mr. Leslie G. McMillion
Mr. Donald B. Gilmore
IV
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TABLE OF CONTENTS
Page
ABSTRACT ''
ACKNOWLEDGMENTS iv
LIST OF FIGURES viii
LIST OF TABLES '*
SECTION I - INTRODUCTION 1
SECTION II - GROUNDWATER POLLUTION CASE HISTORIES AND
EVALUATION OF MONITORING TECHNIQUES 3
BRINE DISPOSAL IN ARKANSAS 3
Background 3
Description of Area 4
Monitoring Methods 6
Critique of Monitoring Project 8
PLATING WASTE CONTAMINATION IN
LONG ISLAND, NEW YORK 11
Background 11
Mapping of Plume 12
Steps That Could Have Been Taken 15
What Should Have Been Done 16
LANDFILL LEACHATE CONTAMINATION
IN MILFORD, CONNECTICUT 17
Background 17
What Could Have Been Done 21
What Should Have Been Done 22
POLLUTION POTENTIAL OF AN OXIDATION
POND NEAR TUCSON, ARIZONA 22
Site Description 22
Map of Nitrate Levels 24
Rationale of Project 25
What Could Have Been Done 28
What Should Have Been Done 30
MULTIPLE-SOURCE NITRATE POLLUTION IN THE
FRESNO-CLOVIS, CALIFORNIA, METROPOLITAN AREA 32
Background 32
Summary of the Monitoring Program 33
Description of Alternative Monitoring Programs 40
Strengths and Weaknesses of Monitoring Program 41
Description of Optimal Monitoring Program 41
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CONTENTS (continued)
Page
SECTION III - SITE-SPECIFIC GROUNDWATER QUALITY
MONITORING EXAMPLES 42
AGRICULTURAL RETURN FLOW 42
Land Surface Monitoring 43
Vadose Zone Monitoring 43
Saturated Zone Monitoring 44
AGRICULTURAL RETURN FLOW EXAMPLE 44
Step 2 Identify Pollution Sources, Causes,
and Methods of Waste Disposal 44
Step 3 Identify Potential Pollutants 44
Step 4 Define Groundwater Usage 45
Step 5 Define Hydrogeologic Situation 45
Step 6 Study Existing Groundwater Quality 45
Step 7 Evaluate Infiltration Potential of Wastes
at the Land Surface 46
Step 8 Evaluate Mobility of Pollutants from the
Land Surface to the Water Table 46
Step 9 Evaluate Attenuation of Pollutants in the
Saturated Zone 47
Step 11 Evaluate Existing Monitoring Programs 47
Step 12 Establish Alternative Monitoring Approaches 47
Step 13 Select and Implement the Monitoring
Program 49
SEPTIC TANKS 52
Land Surface Monitoring 53
Vadose Zone Monitoring 53
Saturated Zone Monitoring 54
SEPTIC TANK EXAMPLE 54
Step 2 Identify Pollution Sources, Causes,
and Methods of Waste Disposal 54
Step 3 Identify Potential Pollutants 55
Step 4 Define Groundwater Usage 55
Step 5 Define Hydrogeologic Situation 55
Step 6 Study Existing Groundwater Quality 56
Step 7 Evaluate Infiltration Potential of Wastes
at the Land Surface 56
Step 8 Evaluate Mobility of Pollutants from the
Land Surface to the Water Table 57
Step 9 Evaluate Attenuation of Pollutants in
the Saturated Zone 57
Step 11 Evaluate Existing Monitoring Programs 57
Step 12 Establish Alternative Monitoring Approaches 57
Step 13 Select and Implement the Monitoring
Program 58
VI
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CONTENTS (continued)
Page
PERCOLATION PONDS AND LINED PONDS 60
Land Surface Monitoring 60
Vadose Zone Monitoring 61
Saturated Zone Monitoring 62
PERCOLATION POND EXAMPLE 62
Step 2 Identify Pollution Sources, Causes/
and Methods of Waste Disposal 62
Step 3 Identify Potential Pollutants 62
Step 4 Define Groundwater Usage 63
Step 5 Define Hydrogeologic Situation 63
Step 6 Study Existing Groundwater Quality 63
Step 7 Evaluate Infiltration Potential of Wastes
at the Land Surface 63
Step 8 Evaluate Mobility of Pollutants from the
Land Surface to the Water Table 63
Step 9 Evaluate Attenuation of Pollutants in the
Saturated Zone 64
Step 11 Evaluate Existing Monitoring Programs 64
Step 12 Establish Alternative Monitoring Approaches 64
Step 13 Select and Implement the Monitoring
Program 66
SOLID WASTE LANDFILLS 70
Land Surface Monitoring 70
Vadose Zone Monitoring 71
Saturated Zone Monitoring 71
SOLID WASTE LANDFILL EXAMPLE 71
Step 2 Identify Pollution Sources, Causes,
and Methods of Waste Disposal 71
Step 3 Identify Potential Pollutants 72
Step 4 Define Groundwater Usage 72
Step 5 Define Hydrogeologic Situation 72
Step 6 Study Existing Groundwater Quality 72
Step 7 Evaluate Infiltration Potential of Wastes
at the Land Surface 73
Step 8 Evaluate Mobility of Pollutants from the
Land Surface to the Water Table 73
Step 9 Evaluate Attenuation of Pollutants in the
Saturated Zone 73
Step 11 Evaluate Existing Monitoring Programs 73
Step 12 Establish Alternative Monitoring Approaches 74
Step 13 Select and Implement the Monitoring
Program 75
REFERENCES 77
APPENDIX-METRIC CONVERSION TABLE 81
vii
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LIST OF FIGURES
Figure No. Title Page
1 Location of polluted areas. 4
2 Contours of chloride concentration at bottom of alluvium. 9
3 Section A-A' showing brine distribution. 10
4 Map showing plating-waste plume, water-table contours, and
selected test wells . 13
5 Vertical profiles of hexavalent chromium and cadmium along
the center line of the plating-waste plume. 14
6 Three major groundwater environments as delineated by inter-
pretation of resistivity data 15 to 20 feet below land surface,
Milford, Connecticut. 18
7 Schematic hydraulic profile along section A-A1 of Figure 6,
Milford, Connecticut. 19
8 Location of pond near Tucson, Arizona. 23
9 Nitrate and chloride distribution in wells near the pond site,
October 1971. 25
10 Location of monitoring facilities at the pond site. 26
11 Map of part of the San Joaquin Valley, California. 32
12 Chloride concentration contours (mg/l) in groundwater at and
downgradient of Fresno sewage treatment plant., 35
13 Chloride concentration contours (mg/l) in groundwater east
of the Fresno sewage treatment plant. 36
14 Relation between aquifer penetration and 1970 nitrate for
wells in Figarden-Bullard area. 36
15 Short-term trends in nitrate during pump test on a large-
capacity well in FCMA. 37
16 Seasonal trends in nitrate and chloride for a large-capacity
well in a septic tank area. 37
17 Study areas in the Fresno-Clovis Metropolitan Area. 38
18 Nitrate concentrations in groundwater near Fresno sewage
treatment plant. 39
*
VIII
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LIST OF TABLES
Table No. Title Page
1 Well-construction costs for vadose zone monitoring 49
2 Costs for vadose zone monitoring 51
3 Total costs for agricultural return flow monitoring 52
4 Cost summary for monitoring septic tank pollution 59
5 Costs for monitoring the vadose zone 67
6 Costs for saturated zone monitoring 69
7 Total costs for monitoring industrial waste percolation pond 69
8 Monitoring costs for solid waste landfill 76
IX
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SECTION I
INTRODUCTION
This report is designed to serve as a companion report to two other doc-
uments Monitoring Groundwater Quality; Monitoring Methodology (Todd
et al. , 1976) and Monitoring Groundwater Quality; Methods and Costs (Ever-
ett et al. , 1976). The first report presents the following 15-step method-
ology for monitoring groundwater quality degradation resulting from man's
activities:
Step 1 Select Area or Basin for Monitoring
Step 2 Identify Pollution Sources, Causes, and Methods of
Waste Disposal
Step 3 Identify Potential Pollutants
Step 4 Define Groundwater Usage
Step 5 Define Hydrogeologic Situation
Step 6 Study Existing Groundwater Quality
Step 7 Evaluate Infiltration Potential of Wastes at the
Land Surface
Step 8 Evaluate Mobility of Pollutants from the Land Surface
to Water Table
Step 9 Evaluate Attenuation of Pollutants in the Saturated
Zone
Step 10 Prioritize Sources and Causes
Step 11 Evaluate Existing Monitoring Programs
Step 12 Establish Alternative Monitoring Approaches
Step 13 Select and Implement the Monitoring Program
Step 14 Review and Interpret Monitoring Results
Step 15 Summarize and Transmit Monitoring Information
Application of these 15 steps by a Designated Monitoring Agency (DMA), be
it at the Statewide or local level, will result in the selection of the area to
be monitored and the identification and prioritization of pollution sources
and causes for monitoring. The second report summarizes specific
1
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techniques for monitoring groundwater quality together with detailed esti-
mates of their costs.
In many instances government and industrial organizations divide moni-
toring responsibilities among their various departments according to activ-
ities such as agriculture, mining, public health, etc. As a consequence,
classes of pollution sources, e.g., irrigation return flow, waste-water treat-
ment and disposal, and solid waste disposal, have become institutionalized
along similar lines. Individuals with a responsibility for monitoring such
class-specific problems are not likely to be interested in the complete 15-
step areawide monitoring methodology, but instead will want to know how to
deal with a particular pollution source. Sections II and III of this report
have been specially prepared to illustrate the application of site-specific
monitoring methodology.
Section II presents a critique of five actual groundwater pollution case
histories given with the monitoring techniques which were employed as well
as a retrospective view of these techniques and their efficacy. The five case
histories are as follows: Brine Disposal in Arkansas; Plating Waste Con-
tamination in Long Island, New York; Landfill Leachate Contamination in
Milford, Connecticut; Pollution Potential of an Oxidation Pond Near Tucson,
Arizona; and Multiple-Source Nitrate Pollution in the Fresno-Clovis, Cali-
fornia, Metropolitan Area.
Section III presents illustrative examples of how to apply those steps of
the methodology applicable in site-specific situations to the following pol-
lution sources: (Agricultural Return Flow, Septic Tanks, Percolation Ponds,
and Solid Waste Landfills. ) Steps 1, 10, 14, and 15 are omitted from the
discussion because the area will already have been specified and the priority
of the sources for monitoring established. In addition, the review, interpre-
tation, and transmission of the monitoring results will be a function of the
goals of the DMA which are not specified in this instance. The costs for the
monitoring methods selected in each example were obtained from Everett
et al. (1976).
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SECTION II
GROUNDWATER POLLUTION CASE HISTORIES AND
EVALUATION OF MONITORING TECHNIQUES
BRINE DISPOSAL IN ARKANSAS
Background
Disposal of the salt water produced along with the oil from oil -wells has
long been a pollution problem. Prior to the 1960s the salt water was com-
monly placed in "evaporation" pits as a disposal method. Pits dug into an
impermeable formation or lined would generally function as intended; how-
ever, in most cases, considerable saltwater infiltrated downward to pollute
the groundwater. In the older oil fields the use of such pits was widespread
and, even though many pits have been filled and are no longer visible,
plumes of polluted groundwater are still present.
Today oil-field brines are more commonly disposed of through wells.
Saltwater disposal wells can be classified in increasing order of safety from
pollution as follows: (1) disposal through the annulus between the surface
casing and production casing, (2) disposal using a converted abandoned oil
well, and (3) disposal in a well specifically designed and drilled for salt-
water disposal. The most common causes of pollution associated with salt-
water disposal wells are (1) corroded or broken casing allowing the salt-
water to escape into a fresh-water aquifer and (2) excessive injection pres-
sure resulting in upward movement of brines outside an improperly cemented
casing or through fractures in containing formations.
The groundwater pollution discussed in this subsection was caused by dis-
posal of oil-field brine first through an "evaporation" pit and later through a
faulty disposal well (Fryberger, 1972). The scope of the original report in-
cludes the following:
A history of the cause of the pollution
Determination of the extent of pollution
Evaluation of chemical changes in the polluting
brine
Cost-benefit evaluation of potential remedial
measures.
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Description of Area
LOCATION. The polluted area is in Miller County in the southwest corner
of Arkansas (Figure 1). The site selected for detailed investigation is 2-1/2
miles* southwest of Garland City on the floodplain of the Red River and about
2-1/2 miles west of the present river channel.
0 10 20 30 40
I I I I I
SCALE-miles
ARKANSAS
MILLER COUNTY
POLLUTED AREA
(GARLAND)
LOUISIANA
Figure 1. Location of polluted areas.
GEOLOGIC SETTING. The floodplain of the Red River is 9 miles wide in
the project area and is characterized by oxbow lakes and poorly drained
bayous, typical of a mature, meandering, aggrading river. Clean, highly
permeable sand was deposited by the river during much of its early deposi-
tional history. In the polluted area the alluvial sand extends to a depth of
40 feet, but elsewhere the alluvium extends up to 90 feet (Ludwig, 1973).
Alluvial clays and silts extending from ground surface to a depth of about
12 feet overlie the alluvial sands in the polluted area. The bedrock under-
lying the alluvium consists of sedimentary formations of Eocene and Creta-
ceous ages.
The static water level in the alluvium is about 8 feet below ground level
in the polluted area. This alluvial aquifer is the most commonly tapped
water source in the County for municipal, domestic, and agricultural water
uses.
*See Appendix for conversion to metric units.
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HISTORY. In 1967 a farmer owning land adjacent to the polluted area
complained to State agencies that his 1,000 gallons per minute (gpm) irriga-
tion well had turned salty.
During the summer of 1967 interested State agencies with overlapping
jurisdiction (Arkansas Soil and Water Conservation Commission, Arkansas
Geological Commission, Pollution Control Commission, and the Oil and Gas
Commission) conducted a preliminary investigation to determine the source
of the pollution. This investigation consisted of sampling the sand-water
mix brought to the surface by a continuous auger-type drill in the area around
the nearby "evaporation" pit. These preliminary test hole samples strongly
suggested that the "evaporation" pit was the source of the polluting brine.
In addition, under a reconnaissance study being conducted simultaneously
by the U. S. Geological Survey, groundwater samples were obtained over a
20-square mile area along the Red River in Miller County. This more gen-
eral study delineated two other polluted areas where chlorides exceeded 500
milligrams per liter (mg/1). Pollution of all three of the areas is believed
caused by improper disposal of oil-field brines through "evaporation" pits,
two of which had been abandoned and filled in. The operator of the remaining
"evaporation" pit was ordered to fill the pit and dispose of the brine using
some other means. An abandoned oil well next to the pit was then used by
the operator as a disposal well.
Funded by an EPA grant, the Arkansas Soil and Water Conservation Com-
mission conducted a detailed investigation of the polluted area using numer-
ous test/observation wells. During this investigation it was noted that
periods of water-level rises in an observation well 500 feet from the disposal
well correlated with periods of saltwater injection into the disposal well.
Further investigation revealed that when the disposal well was first put into
operation, injection pressures of 300 to 400 pounds per square inch (psi)
were required to pump the brine into the disposal formation at a depth of
about 2500 feet. However, at the time of observation no injection pressure
was required to inject the brine at the same flow rate. Based on these facts
and other observations it was determined that most of the brine then being
pumped was escaping from the disposal well through a corroded or faulty
surface casing and was being injected into the fresh-water alluvial aquifer.
A new injection well was then constructed nearby for disposal of the brine.
The continued pollution through the original faulty disposal well could have
been avoided had the appropriate State agency required monitoring of a fluid-
filled annulus outside of the tubing to detect leaks.
The investigation of the Arkansas Soil and Water Conservation Commission
was completed with preparation of the report, "Rehabilitation of a Brine-
Polluted Aquifer, " Fryberger (1972).
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Monitoring Methods
OBJECTIVES. Objectives of most investigative projects can be divided
into two categories. The first includes general objectives that are common
to most investigations of a similar nature; the second includes special objec-
tives not common to all projects of a similar nature.
The general objectives of this investigation were to (1) delineate the lat-
eral and vertical areal extent of pollution and the gradation in concentration
away from the source, (2) positively identify the source, and (3) determine
the rate and direction of movement of the pollution plume by determining the
transmissivity of the aquifer and the slope of the water table.
The special objectives of the investigation were to (1) determine the chem-
ical changes taking place in the aquifer as a result of the polluting brine
mixing with the native groundwater and the formation of solids in the aquifer,
(2) determine the present and future monetary loss caused by the pollution,
and (3) determine the technical and economic feasibility of rehabilitation of
the aquifer by removing the saltwater.
Further discussion of the monitoring program is limited to the three
general objectives and to the first special objective.
EXPLORATION ALTERNATIVES. The selection of specific monitoring
methods from the wide choices available is primarily dependent on the ob-
jectives and the geologic conditions in the project area, and is secondarily
dependent on relative reliability and costs of the alternate choices.
Three alternate general exploration methods of collecting the data re-
quired to meet the objectives of the investigation were considered. These
were: (1) drill test holes, install permanent casing, and obtain water sam-
ples, (2) conduct a surface resistivity survey (supplemented by drilling and
sampling), and (3) rotary drillholes (uncased) and run electric logs on the
holes (supplemented by casing and sampling).
The first alternate, drilling test holes, installing permanent casing, and
obtaining water samples, was chosen as the general exploration method be-
cause it is the only monitoring method of the three that provided the means
to achieve all of the objectives. It offered the advantages of:
Ability to determine both lateral and vertical distribution
of brine
Ability to obtain water samples for chemical analysis to
determine chemical changes in the injected brine
Ability to obtain water levels and formation samples to
determine rate of movement of the plume
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Provision for a permanent monitoring system for determining
actual plume movement with time.
Although the cost of drilled and cased monitoring holes is higher than the
alternate choices, the cost was not considered prohibitive because of the
shallow depths and easy drilling provided by the soft geologic formations.
Under different geologic conditions it may have been advantageous to use
the alternate methods to augment or replace some of the cased drill holes.
For instance, if the polluted aquifer were deeper and presented more costly
drilling conditions, then to reduce costs down-the-hole electric logging meth-
ods to determine relative water salinity could be used in place of water sam-
pling at some of the sampling points. In addition, under vertically and later-
ally uniform geologic conditions, surface resistivity could be used to replace
some test holes to help delineate the lateral extent of the pollution at less
cost than the test holes (Oklahoma Water Resources Board, 1974).
DRILLING ALTERNATIVES. Having selected cased holes and water sam-
pling as the exploration method, alternative methods of setting the casing
were considered to best fit the objectives and the requirements of geologic
conditions, cost, and reliability of data. The methods considered were use
of drive points, continuous-flight auger drilling, mud/water rotary drilling,
cable tool drilling, and air rotary drilling. The drilling method selected for
this project was a combination of two alternatives, continuous-flight auger
drilling and drive points.
Two advantages of continuous-flight auger drilling: (1) there is no drilling
fluid to contaminate the native groundwater, and (2) the drilling rigs are
relatively mobile. Disadvantages: (1) formation samples are mixed and ob-
taining an accurate detailed geologic log is not possible, (2) because the un-
consolidated, loose formations, such as saturated sands, cave in, the casing
cannot be set, and (3) drilling is possible only in relatively soft formations.
Drive points, which are pipes with a short, pointed well screen on the
bottom, are driven through the formation to the desired depth. Although
practical for only shallow, soft formations, drive points have the advantages
of low cost and no need for using foreign matter such as drilling fluid;
therefore, water samples can be obtained quickly without fear of contamina-
tion. However, because no samples of the formation material are obtained
in the process, detailed geologic logs cannot be constructed. Also, deter-
mination of aquifer transmissivity and rate of movement of the plume is
much less reliable without formation samples.
In sinking the well shafts, a continuous-flight auger was used to drill a
hole down through the 10 to 15 feet of clayey soil overlying the sand aquifer.
This method was fast and economical for that specific part of the work, but
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not suited for drilling the entire hole because the loose sand aquifer would
not stand open. Drive points with 2-inch pipe were then set into the open hole,
drilled through the remaining clay, and mechanically driven to the desired
depth in the sand aquifer. The drive points could not be driven through the
clay because excessive force would have been required and the clay would
have sealed off the drive point well screen.
This approach made it feasible to obtain water samples at intermediate
depths as the drive point was being driven to its final depth. The bottom of
the soft alluvial sand was detected when the, drive point reached the hard
underlying bedrock.
Water samples were obtained by pumping with a centrifugal pump attached
directly to the top of the drive point pipe. If the water table had been lower
than about 20 feet, then other pumping methods such as a submersible or
turbine pump would have been required and a larger-diameter casing would
have been necessary.
The primary disadvantage of the method selected is the lack of aquifer
formation samples obtained. This made it more difficult to determine aqui-
fer transmissivity necessary to calculate the rate of movement of the plume.
Pumping tests and sample descriptions from other sources not in the imme-
diate area had to be used for transmissivity estimates.
Critique of Monitoring Project
RESULTS OBTAINED. Twenty-eight sampling sites were located around
the pollution source. At many of the sampling sites water samples were ob-
tained at intermediate depths in order to provide data on the vertical distri-
bution of the brine.
Figure 2 shows the distribution of the sampling sites relative to the pollu-
tion source, the lateral distribution of chloride concentration at the bottom
of the aquifer, and the location of the vertical section through the area that
is depicted in Figure 3.
Generally, the monitoring methods selected for this project were success-
ful in achieving the objectives. The vertical and horizontal distribution of
the chlorides within the polluting plume were determined with sufficient ac-
curacy. A survey of water level elevations in all the test wells plus adja-
cent domestic wells provided accurate data to calculate the slope of the water
table. Good water samples were obtained from the test wells to meet both
the general and special objectives, and additional water samples were ob-
tained from adjacent domestic wells to determine background quality.
RECOMMENDED CHANGES. In retrospect, two changes would be desir-
able if the project were to be repeated. One change involves a general ob-
jective, and the other a special objective.
8
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SCALE-feet
SOURCE: FRYBERGER, 1972
LEGEND
o5
-500-
A-A1
OBSERVATION WELL LOCATION AND NUMBER
CHLORIDE CONCENTRATIONS IN mg/IUer
LOCATION OF CROSS SECTION DEPICTED IN
FIGURE 3
Figure 2. Contours of chloride concentration at bottom of alluvium.
First, a rotary drill using clear water for a drilling lubricant would be
used in place of an auger and drive points. Rotary drilling would permit
sampling of the aquifer formation in order to better evaluate the aquifer
transmissivity for calculating the rate of movement of the polluting plume.
This procedural change would entail (1) drilling and sampling the hole, (2)
setting casing with a short screen on the bottom to the desired depth, and
(3) pumping for a sufficient time to clear all of the drilling fluid out of the
formation. The length of pumping time required would be determined by
monitoring the pumped water in the field using a. portable specific conduc-
tivity meter.
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The second change would be to conduct certain key chemical analyses such
as for pH, CG>2 (carbon dioxide), and HCO3 (bicarbonate) either in the field
or, if in a laboratory, shortly after samples were obtained to provide better
quality data for the objective of determining chemical changes in brine as
it mixed with the native water and aquifer solids.
PLATING WASTE CONTAMINATION
IN LONG ISLAND, NEW YORK
Background
In 1942, the Nassau County Department of Health, Long Island, N. Y. ,
undertook a routine survey of the water-supply system in a former aircraft
plant at South Farmingdale. The survey revealed that water from a well
near a basin used to dispose of wastes from metal-plating operations at the
plant contained about 0. 1 mg/1 of chromium.
The plating-waste contaminants were derived from chemical solutions
used chiefly in anodizing and other metal plating processes, starting in
about 1941. Until several years after World War II, large quantities of
virtually untreated plating-waste effluents were recharged into the ground-
water through disposal basins. Only scanty records were kept of the quan-
tities, but it is estimated that during the early 1940s, as much as 200,000
to 300,000 gallons of effluent, containing about 52 pounds of chromium and
smaller amounts of other metals, was recharged daily into the upper glacial
aquifer. After the war, the quantities of effluent were reduced substantially
and the character of the waste changed to some extent.
It was not determined initially whether the chromium was in the nontoxic
trivalent ion or the toxic hexavalent ion, but the plant management was ad-
vised by the Health Department to prohibit the use of water from the contami-
nated well for drinking purposes and to initiate treatment for removal of
chromium from the plating wastes.
Nothing further was done until 1945, -when the Department of Water Supply,
Gas, and Electricity of the City of New York installed a series of shallow
test wells in an area several hundred feet south of the aircraft plant. This
work was undertaken because the City was concerned over potential contami-
nation of its auxiliary groundwater system at Massapequa, several miles to
the south. The chromium content of the water from the test wells, which
penetrated the water table for only a short distance, ranged from zero to a
trace, and consequently City officials decided that no real threat to the water
system existed.
In 1946, after the U. S. Public Health Service established a limit of 0. 05
mg/1 for hexavalent chromium in drinking water, the New York State De-
partment of Health requested that the new owners of the metal-plating
11
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facilities present plans for the removal of chromium from the plating wastes
before disposal into the groundwater reservoir. In 1948, the New York State
Department of Health analyzed another set of samples from the test wells
drilled in 1945 and also took samples from a shallow domestic well about
1500 feet south of the disposal basins. The results showed about 1 to 3.5
mg/1 of hexavalent chromium, 0 to 0. 24 mg/1 of cadmium, and 0. 06 to 0. 16
mg/1 of copper and aluminum. In conformance with recommendations of the
County and State Health Departments, a waste-treatment unit for chromium
was placed in operation in 1949, but discharge of the effluent containing cad-
mium and other metals continued at the disposal basins.
HYDROGEOLOGIC SETTING. The groundwater reservoir in the South
Farmingdale area consists of about 1300 feet of saturated consolidated de-
posits resting on crystalline bedrock. In general, this sedimentary sequence
is divided into three principal aquifers or water-bearing units. The upper
glacial aquifer extends from the water table, at depths of less than 15 feet
below land surface, to the top of the second aquifer, referred to as the Mago-
thy aquifer. The upper glacial aquifer consists mainly of beds and lenses of
fine-to-coarse sand and gravel. The Magothy aquifer, whose upper surface
ranges from about 80 to 140 feet below land surface, consists chiefly of beds
and lenses of fine sand, sandy and silty clay, and clay. The third aquifer,
the Lloyd sand member of the Raritan formation, lies more than 1, 000 feet
below land surface. Only the upper glacial aquifer was affected by the con-
tamination.
The general direction of groundwater movement in the upper glacial aqui-
fer is toward the south, and the shallow groundwater in the area of the study
eventually discharges into Massapequa Creek. Water enters the upper gla-
cial aquifer by direct infiltration of precipitation and by lateral subsurface
inflow.
DIMENSIONS OF PLUME. Figures 4 and 5 show a plan view and vertical
sections of the plume of hexavalent chromium and cadmium contamination,
as defined by the test drilling and sampling. The plume was as much as
4, 300 feet long and 1, 000 feet wide in 1962. In the vertical dimension, it ex-
tended from the water table to depths of as much as 50 to 70 feet below land
surface. Maximum concentrations of hexavalent chromium, which were as
much as 40 mg/1 in 1949, had decreased to about 10 mg/1 in 1962. Concen-
trations of cadmium were as high as 3 mg/1 in 1962, and as high as 10 mg/1
in 1964 at a spot not previously tested.
Mapping of Plume
Aware of the potential danger to public water supplies, the Nassau County
Departments of Health and Public Works began a systematic investigation of
the plume in 1949 with the drilling of about 40 test wells along several streets
12
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730i081
Legend
O No heavy metals
Hexovalent chromium and cadmium
© Cadmium only
Hexavalent chromium only
48 i_ Contour on water table and direction
* of ground water flow. Datum is mean 55
Figure 4. Map showing plating-waste plume, water-table contours, and
selected test wells (modified after Perlmutter and Lieber, 1970).
13
-------
-D
D O
0)
**- C
0 I
0> D.
o t;
-M
1 1
(D _2
> Q.
10
0)
D
O)
14
-------
south of the disposal basins (Figure 4). These wells were 1-1/4-inch driven
points which were sampled by hand pumping at 5-foot intervals. Drilling was
continued to depths (generally 50 to 60 feet) at which field testing showed no
evidence of chromium contamination. Maps and profiles of the plume were
prepared for the first time from the results of this drilling (Suter et al. ,
1949).
In 1953, 1958, and 1962, additional test wells were installed to map
changes in the boundaries of the plume and changes in concentrations of the
cadmium and chromium. In the 1962 investigation, which was the most de-
tailed of the series, about 100 sampling wells were installed and several
test holes were drilled in which cores were taken to define the lithology and
hydraulic coefficients of the geologic units in more detail. Extensive sam-
pling of Massapequa Creek and underlying beds also was undertaken to de-
termine the concentration and load of heavy metals at various points in and
beneath the stream. Spectrographic analyses of several water samples were
made to determine the presence of metals other than cadmium and chro-
mium. Detailed maps and cross sections of the plume again were prepared,
a water budget calculation was made, and the pattern of movement of con-
taminated water from the shallow aquifer into the stream was delineated
(Perlmutter and Geraghty, 1963; Perlmutter et al. , 1963).
Steps That Could Have Been Taken
The basic objectives of the investigation were somewhat limited, and were
focused mainly on defining threats to drinking-water supplies, especially to
the groundwater facility operated by the City of New York and to private
wells in the area. Although a relatively large expenditure was made on the
study, several approaches were not tried that might have yielded better in-
formation and might have led to a better understanding of the occurrence
and behavior of the plume. These other approaches are surface resistivity
surveys, more comprehensive chemical analyses, pumping tests, and con-
taminant transport modeling.
SURFACE RESISTIVITY SURVEY. Surface resistivity surveys might
have proven of value by detecting changes in subsurface conductivity caused
by differences in the conductivities of the native and contaminating fluids.
Such surveys are simple to conduct, do not require extensive test drilling,
and offer a quick way of mapping the broad dimensions of a plume. Al-
though they do not provide quantitative information on the mineral composi-
tion of the plume, they may be useful in selecting areas within which drill-
ing should be undertaken. The success of such surveys depends on the de-
gree of contrast in conductivities and on the depths of the fluids to be de-
tected.
15
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COMPREHENSIVE CHEMICAL ANALYSES. Some of the samples taken
during the investigation should have been analyzed for more chemical con-
stituents, especially other heavy metals and trace elements. Spectrographic
analyses could have been made at the start of the investigation to at least
define the presence of rare or exotic constituents.
HYDRAULIC PROPERTIES OF THE AQUIFER. No pumping tests were
conducted to define the water-bearing properties of the upper glacial aquifer,
and most of the information developed in the study was obtained empirically
through test drilling and sampling. It is likely that a better knowledge of the
hydraulic behavior of the groundwater system at the site could have expedited
the evaluation of the problem and saved some of the costs of drilling. Pre-
dictions of flow velocities, for example, might have been made at an early
stage in order to estimate the probable length of the plume.
CONTAMINANT TRANSPORT MODEL. Another useful step would have
been to develop a mathematical model to predict rates of movement of con-
taminated water and changes in concentration, distribution, and dispersion
of the contaminants. This would require information on such factors as po-
rosity, hydrodynamic dispersion coefficient, hydraulic conductivity of the
aquifer materials, and the thickness and hydraulic conductivity of the stream
bed material in Massapequa Creek, which was the discharge point at the
southern end of the plume. Such a model recently has been made by Pinder
(1973), who predicted that contamination of Massapequa Creek would effec-
tively cease in about 7 years after cessation of disposal or institution of
complete treatment.
What Should Have Been Done
IMPROVED TREATMENT. As with many such projects, after the extent
and composition of the plume had been reasonably well defined between 1949
and 1962, the public agencies decreased the detailed monitoring effort. In
order to abate the contamination, a recommendation was made to the plant
owners to improve the effectiveness of the methods of treating the hexavalent
chromium, but little was done to eliminate other metals in the waste. A
more complete treatment method should have been used to remove all of the
toxic constituents.
SAMPLING OF WELLS AND STREAMS. Although a reasonably good
picture of the extent and movement of the plume was developed during the
detailed field investigation, little has been done since to determine if the
hydrologic situation has altered significantly. No new information has been
obtained, for example, on the attenuation of the plume or whether the con-
tamination has started to move downward into the underlying Magothy aquifer,
which is the principal source of potable water in Nassau County. It is con-
ceivable, with the growing stress being placed on the Magothy aquifer by
public water supply systems, that a downward hydraulic gradient could
16
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develop eventually, with possible long-terra implications to the quality of
drinking water. It probably would be desirable to conduct follow-up studies
involving periodic sampling of strategically located shallow wells and of
parts of Massapequa Creek, and determinations of changes of heads and di-
rections of flow in both the shallow and deep aquifers.
RECOVERY OF CONTAMINANTS. Another step that should have been
given greater consideration is the feasibility of pumping out the contaminated
groundwater for transport to a water-treatment plant or other disposal facil-
ity. The transmissivity of the upper glacial aquifer is reasonably high, so
that even a single shallow pumping well could withdraw a fairly large quantity
of the contaminated groundwater. This could have been tried at least exper-
imentally to show how effective such a procedure would be.
LANDFILL LEACHATE CONTAMINATION
IN MILFORD, CONNECTICUT
Background
In 1973, the State of Connecticut authorized an investigation of a sanitary
landfill site in Milford, Connecticut, that was under consideration as the
location for a new State park. The main objectives of the study were to de-
termine if contamination of the ground and surface waters would prevent the
use of the area for this purpose and whether or not the contamination prob-
lem was severe enough to warrant shutting down the landfill. Drilling and
sampling were carried out to define the chemical quality and pattern of move-
ment of the ground and surface water beneath and adjacent to the landfill,
and an evaluation -was made of gases being generated by the landfill materi-
als (Geraghty and Miller, 1973).
The landfill area,, part of -which is an old fly-ash disposal site formerly
operated by the Devon Power Plant, covers approximately 90 acres. The
refuse is derived from nearby communities and consists largely of ordinary
household wastes, construction rubble, brush and vegetative materials, and
various types of solid and liquid wastes from local industries. A volume -
reduction plant was constructed at the site to shred a portion of the refuse
prior to its deposition in the landfill.
HYDROGEOLOGIC SETTING. The landfill is located on an old tidal
marsh about one-half square mile in area bordering on Long Island (Figure
6). Part of the original marsh is still visible around the landfill materials.
The entire project site was at one time underlain by swamp deposits ranging
from several feet to a few tens of feet in thickness. Directly beneath the
landfill, the marsh deposits have been somewhat compressed and mixed
with fill materials so that they do not show up as a distinct unit in drilling
logs. The marsh is now mostly isolated from tidal effects except for a
small channel in the eastern section. The channel discharges freshwater
during low tide and contains some salty water part way upstream during high
17
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NORTH
-NATURAL GROUNDWATER ENVIRONMENT
'TOO -*1320
LEGEND:
4 80 / 38
/HIGHLY MINERALIZED
\^ GROUNDWATER
/ ENVIRONMENT
48
TREATMENT
PLANT
RESISTIVITY STATION WITH APPARENT
-£° RESISTIVITY VALUE IN ^/mho/cm AT A
SINGLE SELECTED DEPTH
= = = APPROXIMATE LIMIT OF ENVIRONMENT
- LIMIT OF EXISTING LANDFILL
SOURCE: Geraghty and Miller, 1973
Figure 6. Three major groundwarer environment's as delineated by interpretation of
resistivity data 15 to 20 feet below land surface, Milford, Connecticut.
18
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tide. About half of the original marsh area is covered by the artificial fill.
The marsh deposits are underlain by unconsolidated materials about 40 to
60 feet thick (Figure 7). These materials are essentially glacial till and
some outwash sediments, consisting chiefly of layers of fine to medium
sand, silt, and clay. The individual beds do not appear to be very extensive
laterally.
The glacial materials are underlain by consolidated bedrock consisting
primarily of schist and some gneiss. A bedrock valley extends from west
to east across the northern portion of the landfill site. The bedrock slopes
generally to the southeast and an outcrop is present northwest of the land-
fill. The water table ranges in altitude from sea level to about 8 feet above
sea level (Figure 7). The altitude has been raised above its normal level
due to the construction of the landfill mounds.
DIMENSIONS OF PLUME. Because the landfill is in a hydrologic system
of limited areal extent, the contaminated fluid has not moved a great distance
away from the site. In general, a mound of highly contaminated water is
within the landfill materials. The contaminated water moves out radially
from the center of the mound and most of it eventually discharges into Long
Island Sound, only a few hundred feet to the south. Leachate moving to the
west and southwest from the landfill discharges almost immediately into the
60
40
20
LLJ
-20h
Z
o
^ -40
£ -601
-801-
-FRESH WATER
0
400
800
feet
TRANSITION
ZONE
-SALT WATER-
VERTICAL EXAGGERATION : 10 x
LEGEND:
*- GROUNDWATER FLOW
TW 6 WELL NUMBER
f 7.4 WELL SCREEN AND HEAD IN FEET ABOVE SEA LEVEL
^- APPROXIMATE LOCATION OF INTERFACE
Figure 7. Schematic hydraulic profile along section A-A' of Figure 6, Milford, Connecticutc
19
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surface waters in the marsh and the small streams that drain the area. In
some parts of the marsh, the water table is above land surface and has
formed ponds containing leachate.
The investigation showed that some of the groundwater has moved verti-
cally downward to invade deeper zones of the unconsolidated material direct-
ly below the landfill. The quality of the water at these depths is much better
than that of the water in the landfill materials, suggesting that the underlying
fine-grained sediments have been at least partly effective in attenuating the
contamination. Several hundred million gallons of groundwater has been
slightly to heavily contaminated by leachate at the site. A water-budget cal-
culation indicates that about 80, 000 gallons per day of water derived from
precipitation is recharged into the landfill materials, and that an equivalent
amount of contaminated fluid discharges through the bottom and sides of the
landfill.
MAPPING OF PLUME. Initially, background information was reviewed
on topography, vegetation, records of wells and borings, rainfall, tides,
and surface drainage. Following this, seismic and electrical-resistivity
geophysical methods were utilized to give a preliminary idea of the character
and thickness of the materials at the site. In the next step, 36 test observa-
tion wells were drilled in and around the landfill. At some of the well sites,
two wells (one deep and one shallow) were installed to define vertical head
relationships. The wells ranged in depth from 12 to 96 feet.
Periodic measurements of water levels, referenced to sea level, were
made in all wells. Water samples were collected from the wells for chemi-
cal analysis, and where the water levels were below suction lift, the sam-
ples were collected by first blowing water out of the well casings with com-
pressed air and then bailing out the water sample. A field laboratory was
set up to make determinations of some chemical constituents, and samples
were sent to a certified laboratory for more detailed analyses.
Water temperature profiles were made in the deeper wells by means of
an electronic thermometer. Specific-conductance and dissolved oxygen de-
terminations were made on water samples from principal surface water
bodies. Complete chemical and bacteriological analyses were run for some
of these samples.
A series of shallow gas sampling tubes was installed in the landfill at
depths ranging from 3 to 5 feet. Analyses were made to determine the per-
centage of methane in the gas mixture and its explosive levels.
The vegetation was studied by biologists from a local research institute
to define stresses on the vegetation and the relationships with the ground-
water system. Color, stereo, and multispectral photographs were taken
of the landfill and the surrounding area and were used to construct base
20
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maps, establish topographic contours, and define vegetative patterns. The
abnormally high water table, contaminated ground-water, and insect infesta-
tion accounted for most of the stress on the vegetation.
What Could Have Been Done
The information collected during the investigation provided adequate an-
swers to the questions asked by the State, and led to the shutting down of the
landfill. Funds were not allocated in the first stage for a more intensive
monitoring effort, simply because it was not needed. However, a number
of other monitoring steps could have been taken for general research pur-
poses, or to provide data that might have proved useful if an early decision
could have been made on covering the landfill.
GAS GENERATION. The investigation provided some information on the
generation of gases within the landfill. However, no detailed observations
were made to define which types and concentrations of gases were being
generated, where they were concentrated, and the pressure distribution.
More studies could have been conducted along these lines, since ultimately
there would have to be some requirement for venting gases in order to per-
mit multipurpose use of the landfill area.
ADDITIONAL CHEMICAL DETERMINATIONS. Although numerous com-
mon chemical constituents and a few heavy metals such as iron, lead, cop-
per, and manganese were determined in the water samples, little attention
was given to the possible presence of other toxic heavy metals and trace
elements. At some additional expense, these could have been determined
through spectrographic analysis which might have helped detect other toxic
constituents possibly responsible for some of the ecological damage.
BACTERIOLOGICAL STUDIES. Coliform bacteria found in nearby
surface-water bodies were believed to be largely, if not entirely, from con-
taminated materials in the landfill. However, because of the great difficulty
in sterilizing pumps and wells and in disinfecting the environment around the
wells, it was not considered feasible to collect samples of groundwater for
bacteriological analysis. With sufficient funds, time, and suitably con-
structed wells, it would have been possible to study this aspect of the prob-
lem.
ADDITIONAL TEST WELLS. Samples taken from the limited number of
wells drilled directly within the landfill materials showed a wide divergence
in chemical composition, owing partly to differences in the types of materi-
als placed at different locations within the landfill and partly to dilution of
the contaminated water. It would have been useful, therefore, to have in-
stalled a denser grid of sampling wells in order to define particular "hot"
spots of highly contaminated water. The results of such sampling might
have helped locate the sources of particularly objectionable contaminants.
21
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However, problems in constructing wells in the landfill materials and the
fact that the landfill was still in operation during the test program made it
impractical to fully explore the entire landfill area.
INFILTRATION RATES. Another useful procedure would have been to
prepare a more accurate and detailed water budget for the landfill area to de-
termine the rate of leachate production. Field measurements of infiltration,
runoff, and evaporation would have been useful in this regard. However,
the estimates made were considered to be reasonably useful for the purpose
of the investigation, since the landfill was still active at the time and the
rates of leachate production were probably variable.
What- Should Have Been Done
Because of the intention to convert the landfill area into a State park,
more intensive monitoring of stresses on the vegetation during the field
study and following the investigation should have been planned. However,
this additional work was not authorized. Consequently, although the land-
fill is covered over and converted into a recreational area, monitoring has
ceased, although the original test wells still are in place. Additional moni-
toring of vegetative stress and of leachate discharge would prove of consid-
erable value in showing the effectiveness of the landfill cover and of the slow
changes anticipated as the production of leachate slowly diminishes.
POLLUTION POTENTIAL OF AN
OXIDATION POND NEAR TUCSON, ARIZONA*
Site Description
The Ina Road oxidation pond site is located about 10 miles northwest of
Tucson, Arizona, in SE1/4, Section 1, T13S, R12E (see Figure 8). The
site abuts the Santa Cruz River, the principal drainage channel of the Tucson
Basin, and is immediately downstream of the confluences of Canada del Oro
and Rillito Rivers. Discharge in these channels is primarily ephemeral.
However, the Santa Cruz River drains the entire effluent discharge from the
City of Tucson Treatment Plant about 6 miles upstream, as well as overflow
from the Ina Road ponds.
The Ina Road ponds, serving as principal treatment facilities for sewage
in northwest Tucson, are managed by The Metropolitan Utilities Management
Authority. These ponds will be replaced in the near future by a regional
treatment plant of standard design. A sanitary landfill is located along the
Santa Cruz River immediately to the southwest of the ponds.
*The work reported in this subsection was supported in part by a grant from
The Office of Water Research and Technology, U. S. Department of the In-
terior, Washington, D. C.
22
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T13S
IMS
SOURCE: Small, 1973
Figure 8. Location of pond near Tucson, Arizona.
Sediments underlying the pond site are typical of the Basin and Range
physiographic province. Specific geologic units and their water-bearing
properties are discussed by Davidson (1973). The source materials for
these sediments are volcanic rocks from the Tucson Mountains, immediate-
ly to the west, and the granitic rocks of the Santa Catalina and Tanque Verde
Mountains to the east. Principal aquifers in the region comprise surficial
material, Fort Lowell formation and the Tinaja Beds. For the Ina Road
site, Randall (1974) estimated the transmissivities of the aquifers com-
prising the surficial deposits to be between 150,000 - 300,000 gallons per
day per foot (gpd/ft). The corresponding transmissivity of the combined
Fort Lowell and Tinaja Beds aquifer was estimated to be 35,000 gpd/ft.
Depth to the water table at the time of the tests was about 70 feet.
Groundwater flow in the vicinity of the pond is predominantly in a north-
westerly direction, corresponding to underflow in the Santa Cruz River,
but is moderated by southwesterly flow in the Canada del Oro system. Sim-
ilarly, groundwater quality reflects two distinct sources: underflow and re-
charge in the Canada del Oro and Rillito systems; and underflow and re-
charge in the Santa Cruz River, including the contribution of sewage effluent
(Schmidt, 1972a).
23
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An additional complicating factor is that shallow perching layers within
the vadose zone may conduct water laterally at substantial rates (Wilson and
DeCook, 1968). If such layers are hydraulically connected to the Santa Cruz
River, sewage effluent may move laterally from the river into the pond area,
eventually leaking into the water table. Leaching of the landfill deposits by
river seepage is also a distinct possibility and is the subject of a recent
study (Wilson, 1974).
Map of Nitrate Levels
Nitrate was the principal ion considered in the pond study. In general,
groundwater quality in the region downstream of the City of Tucson Treat-
ment Plant is noted for localized high concentrations of nitrate (Matlock et al,
1972; Schmidt, 1972a). Such nitrate may have originated from sewage effluent
recharging in the Santa Cruz River, recharging of effluent applied during ir-
rigation of cropland, leaching of nitrogenous fertilizers, leaching of indige-
nous nitrogen, or leaching of landfill deposits.
One of the major purposes of the study by Wilson et al. (1973) at the pond
site was to monitor the movement of nitrate during deep seepage, particu-
larly during the period immediately after the pond was placed into operation.
Wilson et al. found no positive evidence that lagoon seepage had resulted in
nitrate contamination of groundwater in the area.
The areal distribution of nitrate in wells within the area encompassing the
pond in October 1971, three months after the pond was initiated, is shown in
Figure 9. Data were obtained by the Department of Soils, Water and Engi-
neering, University of Arizona. The two wells sampled in the southeast
quarter, upstream of the pond, contained nitrate levels of 72 mg/1 and 48
mg/1. Wells in the northwest quarter, downstream of the pond, generally
contained nitrate concentrations of about 30 mg/1 except for the furthermost
northwest well, with a level of 45 mg/1.
An irrigation well 300 feet downstream of the pond (see Figure 10) con-
tained 28 mg/1 nitrate in October 1971. The vertical distribution of nitrate
in the profile beneath the pond after several months of pond operation is re-
ported by Wilson et al. (1973). Subsequent nitrate values on 19 April 1973,
within the same profile reported by Wilson and Small (1973) were: 60-foot
PVC well 27. 28 mg/1, No. 1 access well 7. 48 mg/1, and irrigation well
18. 04 mg/1. In 1974 the PVC wells were dry and could not be sampled.
Nitrate levels in the No. 1 and No. 2 access wells were reported by Wilson
(1974) to be 1.2 mg/1 and 1.5 mg/1 respectively. Pump water from the ir-
rigation well contained 11.7 mg/1 nitrate.
24
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R 12E
UPPER VALUES - NITRATE (mg/l)
LOVER VALUES CHLORIDE (mg/H
TI3S
Figure 9. Nitrate and chloride distribution in wells near the pond
site, October 1971.
Rationale of Project
The monitoring program at the pond site was based on experience from
prior studies. One of these studies was conducted at the site before con-
struction of the pond. Other studies were conducted at the University of
Arizona Water Resources Research Center (WRRC) field laboratory about
6 miles south of the pond. The latter studies involved investigations of arti-
ficial and natural recharge, with particular references to mechanisms of
water movement in the vadose zone and water quality changes during such
movement. Results of some of these studies were reported by Wilson and
DeCook (1968) and Wilson (1971). Monitoring facilities included observation
wells, pumping wells, shallow piezometer-water sampling wells, and access
wells. By means of neutron logs in the latter wells, the growth and dissipa-
tion of two perched water tables in the sediments overlying the principal
aquifer were clearly observed. The existence of such perched tables in
surficial deposits of the Tucson Basin has been known for many years. The
advantage of neutron logging is that the location and behavior of the tables
can be followed. Furthermore, knowing the location of regions in which
tables develop, it is possible to terminate sampling wells in sediments
which saturate during recharge. Based in part on such reasoning, two bat-
teries of sampling wells were installed at the WRRC recharge site. Four
wells in each battery terminated within the vadose zone, and a fifth termi-
nated below the water table.
25
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#OOG
ffCQ. o oo-o
-^
IRRIGATION WELL
*2 ACCESS WELL
CCE
--= 585 feet
^109° 02' 99".
0 16' 00"
13' 00'
SEWAGE LAGOON
WATER SURFACE EL. 85.0'
BOTTOM EL. 80.0'
*1 ACCESS WELL
40' PVC WELL
60' PVC WELL
700 feet
N
SANTA CRUZ RIVER
SOURCE: Small, 1973
Figure 10. Location of monitoring facilities at the pond site.
One observation of interest from the recharge study was that water
moved very rapidly (up to 200 feet per day) in the perched layers. In fact
it appeared that the upper layer served essentially to spread water for a
considerable lateral distance away from the recharge source, with leakage
into the lower layers. Furthermore, samples from the wells in the vicinity
of the water table showed a gradual displacement of native groundwater by
recharge effluent, suggesting that recharge effluent flows along the top of
the main, but slower moving, water body. Mixing then takes place by dis-
persion, etc.
The experience gained during the installation and operation of the facili-
ties at the WRRC site prompted the installation and operation of similar
facilities at the oxidation pond site during investigations of grass and soil
filtration in 1967-1968. Results of these investigations were reported by
Wilson and Lehman (1967) and Lehman (1968). Basically, the studies in-
volved metering oxidation pond effluent onto three Bermuda grass plots,
each 25 feet by 1, 000 feet. Two 100-foot access wells were installed on
the central plot. Neutron logging in these wells during preliminary experi-
ments seemed to indicate the presence of two perched layers within the
vadose zone, one at about 30 feet below land surface and a deeper layer at
about 50 feet. Two 4-inch-diameter PVC wells terminating at depths of
26
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40 and 60 feet were then installed by the cable-tool method. Each well
contains a 4-foot-long plastic well screen. PVC was selected as material
for these wells to minimize interference during studies involving the moni-
toring of heavy metals during effluent irrigation. Drill cuttings were ob-
tained during construction of the wells but unfortunately, except for the
upper 8 feet, these cuttings were not examined for physical or chemical
makeup.
In addition to the PVC wells and access wells, the central plot was in-
strumented with three sets of four suction cup batteries, extending 2 feet
below ground surface. These units were installed to permit soil solution
sampling in the unsaturated state.
Results of flooding trials showed that grass filtration was not particularly
effective as an overall, tertiary-treatment technique, compared with soil
filtration. As expected, effluent arriving in the two PVC wells contained
excessive levels of nitrate (in excess of 90 mg/1), but phosphate concentra-
tions were lowered.
In 1970 the Pima County Department of Sanitation began plans for a new
10-acre stabilization lagoon, which would encompass several hundred feet
of the grass plots. The County and City had received unfavorable publicity
a short time before this period due to a threatened lawsuit by a homeowner
near the ponds. The homeowner claimed that he could not drill a well for
fear of nitrate contamination. Although the matter was settled before the
new pond was due to be constructed, the University approached the County
Department of Sanitation with the suggestion that a joint study be undertaken
to monitor seepage from the new pond, with particular emphasis on nitrate
movement. Fortunately, the two PVC wells and one access well were
close enough to the western dyke of the lagoon that it was possible to con-
struct a platform to reach them. The resultant arrangement is shown in
Figure 10. Not shown in Figure 10 are two batteries of ceramic suction
cups, one located on the -western side of the pond and the second near the
eastern side.
With the physical arrangement of -wells shown on Figure 10, it was con-
jectured that a fair representation of the vertical changes in effluent quality
could be obtained during deep seepage. Thus, the shallow suction cups
would provide samples of soil solution, the two PVC wells would sample
from mounds within the vadose zone, the access wells would sample just
below the water table, and the irrigation well would provide an integrated
sample from its perforated region of 80 feet to 278 feet. Also, the two
access wells, one within the pond and one outside, offered the opportunity
to detect the lateral movement of water in the vicinity of the main water
table.
27
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Whaf Could Have Been Done
Additional steps could have been taken to upgrade the monitoring pro-
gram but were not because of limited funds.
An interdisciplinary team could have been assembled to ensure that all
parameters of significance would be monitored during the study. The fol-
lowing disciplines would have been desirable: soil chemistry, soil micro-
biology, soil physics, sanitary engineering, aquatic biology, and hydrology.
An interdisciplinary team would have allowed relating changes in physical,
chemical, and biological properties of the aqueous environment of the pond
to corresponding changes in effluent during flow across the benthic-soil in-
terface and during deep seepage. Some of the specific parameters which
could have been monitored by the team are presented below.
Since the pond site is located in a region of complex hydrogeology at the
confluences of the Canada del Oro and Santa Cruz Rivers, bulk groundwater
flow from the two systems creates a complex effect on flow patterns and
water quality. Also the effect of flood recharge and inflow of sewage ef*-
fluent and landfill leachate through perching layers should be taken into ac-
count. Therefore, a thorough hydrogeological study would have helped to
delineate and separate the interrelated effects, and thereby assisted in in-
terpreting results.
Standard techniques for hydrogeological studies (Walton, 1970) could
have been employed to delineate sources and sinks, boundary conditions,
etc. In addition, test wells could have been constructed to provide drill
cuttings for particle-size analyses and chemical composition. Resistivity
and seismic surveys and down-hole gamma and neutron logging would be
included. Results would have been carefully examined for more precise
delineation of possible perching layers in the vadose zone, as well as re-
gions of varying permeability below the water table.
As part of the hydrogeologic study the team could have attempted to
trace inflow of sewage effluent from the Santa Cruz River by introducing
suitable dyes upstream of the pond and collecting samples of well water.
(Unfortunately, chloride levels are about the same in all sources. )
Based on the hydrogeological studies, additional monitoring facilities
could have been installed around the pond. For example, from moisture
logging (i. e. , neutron probe) data, additional shallow wells could have been
constructed down to perching layers. These wells would have allowed
more accurate examination of the lateral spread of pond effluent through
the layers. Similarly, better estimates could have been made of the mix-
ing in these layers of inflowing sewage effluent (and possibly landfill leach-
ate), natural recharge, and downward flowing pond effluent.
28
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Several deeper observation wells could have been constructed around
the pond. Additional information on aquifer transmissivity and storability
could have been obtained by pumping these wells. Water samples could
have been extracted from various zones beneath the water table in these
wells before and after initiating the pond operation. Data from such a pro-
gram would have provided a picture of the vertical distribution of quality
(e. g. , nitrate content), below the water table and indicated the effects of
dispersion, etc.
A ring of access wells would provide moisture content data via neutron
moisture-logging to facilitate water balance studies.
The drill cuttings obtained as part of the hydrogeological study could
have been examined for chemical composition. In particular, the concen-
tration of indigenous nitrogen and phosphorous in saturated extracts from
the cuttings would have indicated the vertical distribution of these constit-
uents in the vadose zone.
The C:N ratio of sludge within the benthic layer of the pond could have
been evaluated periodically to determine the effects of changes in this ratio
on mineralization of nitrogen (see Miller, in Sopper and Kardos, 1973).
Similarly, soil cores from the soil-benthic interface could have been taken
to determine changes in organic matter, cation exchange capacity (CEC)
and exchangeable cations (particularly ammonium-nitrogen (NH^-N)) . Wil-
son et al. (1973) hypothesize that increase of soil organic matter by pene-
tration of sludge would increase the CEC. Changes in NH^-N or nitrate-
nitrogen (NOg-N) levels in shallow tensiometer samples could have been
examined for a relationship between organic matter content and CEC.
Vertical movement of heavy metals and organic toxins originating in pond
effluent could have been monitored in shallow tensiometers, deeper PVC
wells, and access wells.
An attempt could have been made to install a system of electrodes in the
soil-benthos interface for monitoring redox potential. However, as pointed
out by Ellis (in Sopper and Kardos, 1973) in-situ determination of redox has
not proven to be successful.
Wells constructed for the sampling program could have been used to ob-
tain data for the development and calibration of computer models. In par-
ticular, data could have been obtained to provide realistic estimates of
dispersivity coefficients of aquifer materials.
At the time of the study (1971), a few finite difference models were
available to simulate groundwater flow. Mass transport effects were han-
dled by the method of characteristics. Today finite element models are
29
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being developed to simulate joint hydraulic-mass transport phenomena in
aquifer systems. Such models could be adapted to the pond site.
What Should Have Been Done
Some monitoring programs or techniques that should have been used in
the pond study were not included because of lack of insight or lack of time.
A hydrochemical balance (albeit gross) of the groundwater system of the
area should have been conducted before the pond was placed in operation.
A fair amount of data was readily available for developing such a balance.
For example, the Department of Soils, Water, and Engineering at the Uni-
versity of Arizona had been involved in obtaining hydraulic data of the
Tucson aquifer system for a number of years. These data could have been
examined to estimate flow trends in the vicinity of the pond. In the early
1970s the same department was also actively involved in collecting chemi-
cal data from well-water samples. These data should have been examined
and used to construct trilinear diagrams, etc.
Much data could have been collected from wells in the area; a basic pro-
gram to monitor water levels and quality in nearby domestic and irrigation
wells should have been established. Water levels and chemical data were
obtained in access wells and the irrigation well at the pond site for several
months before the pond was put into operation, but this program should
have been expanded.
The major oversight in the pond study, vis-a-vis the hydrochemical
balance, was in not monitoring seepage of effluent in the Santa Cruz River.
Later studies by Wilson and Small (1973) showed that intake rates of sewage
effluent in the reach of the Santa Cruz River along the pond site are sub-
stantial, ranging from 1. 5 feet per day to 7. 7 feet per day. A program to
monitor trends in the quality of river effluent (including, for example, total
nitrate and boron) should have been implemented before and after the pond
was placed in operation. Resultant data could have been used with ground-
water data to construct trilinear diagrams.
One other possible source of subsurface inflow into the area was not
examined, namely, deep seepage from irrigation across the river from the
ponds. In particular, the movement of leached fertilizers should have been
considered.
Pond overflow should have been metered or sampled. The rationale at
the time was that the various transformations within the aqueous system of
the pond were of interest only as the pond filled. When the groundwater
monitoring program was continued a metering device should have been in-
stalled on the pond overflow and a sampling program established. A nitro-
gen balance of the aqueous system could have been conducted subsequently
30
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to relate to changes in the ground-water system. For example, since the
pond frequently shifted from an aerobic to an anaerobic state, valuable data
could have been obtained on nitrification-denitrification processes. Sam-
ples from the shallow suction cups might have reflected these processes.
Also, a meter on the overflow line would have allowed calculation of long-
term intake rates.
In addition to monitoring seepage rates in the pond by the gross inflow-
change in storage technique, seepage measurements should also have been
attempted at several locations via seepage meters, infiltrometers, etc.
The measurement results should have been related to soil core data on
bulk density, particle size distribution, etc. (Consideration was given to
mounting one or two seepage meters permanently near the platform in order
to relate seepage rates to development of the benthic layer at precise loca-
tions. )
Although the primary purpose of the study was to monitor the movement
of nitrogen species, the chemical data (see Table 2 of Wilson et al. , 1973)
showed that the total phosphate increased from 3. 7 mg/1 to 52 mg/1 in the
40-foot PVC well, and from 6.7 mg/1 to 24. 5 mg/1 in the 60-foot PVC well.
Normally, migration of phosphate in soils and groundwater systems is not
considered a problem and soil filtration studies at the site showed a dimi-
nution of phosphorus during soil filtration. Consequently, the observed
trends should have prompted additional sampling for phosphate beyond the
period of the study. Furthermore, the forms of phosphorus, i. e. , organic
versus ortho or condensed phosphate, should have been determined. A
soil microbiologist could perhaps have related the mobility of indigenous
or effluent phosphate to soil transformations in the soil-benthos region and
underlying zones. (As pointed out by Ellis in Sopper and Kardos (1973), a
soil under reducing conditions will not adsorb as much phosphorus as the
same soil would in well-aerated conditions. )
Although it is known that soils are capable of the chemical filtration of
boron (Ellis, in Sopper and Kardos, 1973), there are cases reported where
boron levels increase in the soil solution during irrigation with sewage ef-
fluent (Bouwer, in Sopper and Kardos, 1973). Therefore, the movement
of boron should have been monitored in the well system at the pond site.
Additional technical details relating to monitoring should have included:
Checking the interaction, if any, of the ceramic materials
used for suction cups with nitrogen, phosphorus, boron, etc.
Installing a system of tensiometers to measure soil moisture
tension near ceramic cups. This would have ensured apply-
ing the proper suction so as not to affect moisture flow
31
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Taking samples periodically to other laboratories as a
quality control measure
Monitoring groundwater temperatures in the network of
wells.
MULTIPLE-SOURCE NITRATE POLLUTION IN THE
FRESNO-CLOVIS, CALIFORNIA, METROPOLITAN AREA
Background
The objective of the Fresno-Clovis study was to determine the extent of
nitrate pollution in the groundwater, the sources of pollution, and time
trends in nitrate content of water pumped by wells.
The Fresno-Clovis Metropolitan Area (FCMA) is a predominantly urban
area of 145 square miles in the central San Joaquin Valley of California
(Figure 11). The surrounding lands are agricultural and rainfall averages
20 miles
i
TO LOS ANGELES
J.
Figure 11. Map of part of the San Joaquin Valley, California.
32
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about 11 inches per year. Groundwater occurs in permeable alluvial de-
posits and water levels average about 70 feet in depth. Wells average
several hundred feet in depth and yields exceeding 1,000 gpm are common.
Groundwater is the sole source of water supply in the urban area, whereas
irrigation demand in the surrounding area is supplied by both canal water
and groundwater. The primary means of liquid waste disposal other than
evapotrans pi ration is by percolation, as there are no significant discharges
to surface water.
Major sources of nitrogen include septic tank effluent in unsewered areas,
sewage effluent, leakage from sewers, fertilizers, and meat-packing plant
and winery wastes. Natural sources of nitrogen do not appear to be of ma-
jor significance and background levels of nitrate in the aquifer are less than
10 parts per million (ppm).
Summary of the Monitoring Program
The two major constraints on the project were time and funding. The
project was a doctoral dissertation, the time available was about 1 year,
and no grant funds were available on such short notice. Thus maximum
use had to be made of existing data and the cooperation of local individuals
and agencies. Limited personal funds were used for research (mainly
photocopying and kits for chemical quality determinations in the field).
The monitoring phase of the project encompassed the folio-wing steps:
1. Determination of the extent of data on groundwater and water
quality in the proposed study area. Sufficient data were avail-
able to warrant proceeding with the program.
2. Completion of an exhaustive literature review on the pollutant
of interest, in this case nitrogen or nitrate. Studies of sources
of nitrogen and the occurrence of nitrate in soils and groundwater
were reviewed (American Water Works Association, 1967;
Schroepfer and Polta, 1969; and Stout et al. , 1965).
3. Collection of all available reports and data on (a) groundwater,
(b) soils, (c) well data, (d) pollution sources, and (e) chemical
analyses of groundwater and pollution sources in the study area
(Behnke and Haskell, 1968; California Department of Water Re-
sources, 1965; Nightingale, 1970; and Page and LeBlanc, 1969).
4. Preliminary evaluation of the areal distribution of sources of
nitrogen and nitrate in groundwater.
5. Collection of supplementary data to fill in gaps; such as water
samples for more extensive areal coverage of groundwater
quality, recent hydrogeologic records, historical development
of nitrogen sources, and chemical analyses of waste waters.
33
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The remainder of the project was interpretation and report preparation
(Schmidt, 1972b and 1975).
COLLECTION OF ADDITIONAL WATER SAMPLES. High capacity
wells (500 to 2500 gpm) were selected for water sampling at the discharge
after prolonged pumping. Localized situations, such as the effect of a
septic tank or lawn fertilizer on groundwater beneath one lot were not of
concern in this study. Low capacity domestic wells (less than 50 gpm)
pumping for short time periods generally reflect very localized conditions.
Water samples taken from high capacity wells after long periods of pumping
are much more indicative of regional conditions, which were of interest in
this investigation. Figures 12 and 13 illustrate the areal distribution of
chloride southwest of Fresno as determined from analysis of water sam-
ples from high capacity wells. Chloride was evaluated in this case because
of its use as a tracer in this area, its being present in waste waters but
almost absent in native groundwater. In the case of point or line sources,
high capacity wells can be used for monitoring at a distance of several hun-
dred or thousand feet from the source. This is due to the lateral extent of
the cone of depression after prolonged pumping.
Because nitrate content varies vertically in groundwater, well construc-
tion is an important parameter in the selection of monitor wells. Figure 14
illustrates the vertical distribution of nitrate in a septic tank area of the
FCMA as determined from pumping of open-bottom (unperforated) -wells.
Highest nitrates occur in the shallowest part of the aquifer. Because of this
vertical stratification of water quality, nitrate contents of well water often
change with pumping time over short time periods. Short-term trends in
some cases can be plotted as straight-line relations on semilogarithmic
graph paper (Figure 15). Seasonal fluctuations were also considered in
evaluating chemical analyses of water samples from monitor wells (Figure
16). Short-term and seasonal trends must be established before long-term
time trends can be evaluated.
As a number of individuals and agencies operate wells within the FCMA
and no uniform monitoring program for ground-water quality exists, the
existing chemical analyses are often for water samples taken at different
times. It was desirable to sample many wells over a period of several
days to several weeks to establish the areal and vertical distribution of
nitrate at a specific time. The optimum sampling time was during the
warmest time of the year, when the maximum pumpage occurred from high
capacity wells. This served two purposes: (1) sampling was much easier
with almost all wells already pumping, and (2) the most typical chemical
quality of the regional groundwater could be monitored.
Several hundred municipal wells were sampled by one individual within
2 or 3 days. This was because only five or six agencies operated these
wells. Sampling of irrigation wells southwest of the urban area took much
34
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PLANT NO
/SEWER FARM ','
W/////////////,
PLANT NO. 2
INFERRED CONTOUR
WELL SAMPLED 8/72
CHLORIDE CONCEN,
TRATION(mg/l)
Figure 12. Chloride concentration contours (mg/l) in groundwater at and
downgradient of Fresno sewage treatment plant.
35
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LEGEND:
WELLS
MAJOR TRUNK SEWERS
Figure 13. Chloride concentration contours (mg/l) in groundwater east of the Fresno
sewage treatment plant.
200
z
o
I
$
I
LU
s
5
O
<
'1
10 15 20 25 30 35
NITRATE (ppm)
Figure 14. Relation between aquifer penetration and
1970 nitrate for wells in Figarden- Bui lard area.
36
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20
18
O 16
QC
I
Z
LU
U
Z
O
I
Z
CITY OF FRESNO
WELL PS 77
JUNE 24, 1970
2 5 10 20
TIME SINCE PUMPING STARTED (min)
Figure 15. Short-term trends in nitrate during pump test on a
large-capacity well in FCMA.
100
50
40
30
20
40
a.
O
x
u
30
20
10
FCWD PUMP 2-1
1972
1973
Figure 16. Seasonal trends in nitrate and chloride for a
large-capacity well in a septic tank area.
37
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longer because of access problems (poor roads), individual ownership in
many cases, and lack of a faucet or open discharge. Because nitrate con-
tent can change with storage time, determinations were made immediately
after collection. Electrical conductivity, water temperature, and chloride
content were also measured.
SITE SPECIFIC DATA AND INTERPRETATION. The FCMA was sub-
divided on the basis of the predominant nitrogen source and on hydrogeology
and the areal distribution of nitrate in the aquifer. This subdivision (Figure
17) was probably the key aspect of the entire study. The Figarden-Bullard
area and Fresno sewage treatment plant were selected because of the pre-
dominance of one nitrogen source in each case (septic tanks and sewage ef-
fluent, respectively). Evidence gained from studies in these areas was
then used in the Tarpey Village and Mayfair- Fresno Air Terminal areas,
where both sources as well as others were present. The latter two areas
had the highest nitrates in groundwater of the urban area. The Downtown
Fresno area had no obvious source, but high nitrate contents were present
in the aquifer. Each area had distinct hydrogeologic conditions with respect
to the other areas.
In areas of diffuse sources, such as septic tanks or fertilizers, semi-
annual analyses are often sufficient to detect seasonal trends. However,
near point sources of large volume, such as the Fresno sewage treatment
plant disposal ponds, weekly or monthly sampling of wells is necessary
R.19 E. R.20 E. R.21 E.
FIGARDEN-BULLARD
I AREA
CITY OF FRESNO SEWAGE
'TREATMENT
T.
12
S.
T.
14
s.
Figure 17. Study areas in the Fresno-Clovis Metropolitan Area.
38
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(Figure 18). The density of existing wells is generally sufficient to delin-
eate the areal water quality distribution. Open-bottom wells drilled by the
cable-tool method are especially valuable as they tend to draw water from
specific depth zones and thus give an indication of vertical stratification of
groundwater quality. Other constituents, such as chloride, potassium,
ammonium, and calcium are valuable in differentiating among various
sources of nitrate. Trilinear diagrams can be prepared for waste waters
and groundwater to illustrate similarities in chemical types of water. His-
torical chemical analyses in the FCMA have documented the buildup of ni-
trate in groundwater due to the development of nitrogen sources at certain
times.
SPECIAL CASES AND ASSUMPTIONS. The travel time of recharged
waste waters from the land surface through the vadose zone to the water
table is in terms of weeks, months, or several years in the FCMA. Cal-
culations on the water budget indicate that near point sources in particular,
wastes must move rather rapidly to the water table. If not, there would be
no storage space in the vadose zone for storage of these large volumes of
water. Hydrographs of water levels and water quality data as related to
land surface phenomena confirm that movement of water through the vadose
zone is relatively rapid.
In the particular case of nitrate, which originates usually as organic
or ammonium nitrogen at the land surface, there is no gross uptake in the
vadose zone, as might be the case for certain trace metals. The fate of
50 1-
40
I
o
I
z
O
u
30
20
WINERY
SEASON
WINERY
SEASON
ASONDJFMAMJJA SOND
Figure 18. Nitrate concentrations in groundwater near
Fresno sewage treatment plant.
39
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most of the nitrogen applied at the land surface is (1) plant uptake, (2)
denitrification and loss to the atmosphere, or (3) nitrification and leaching
to the groundwater. In this particular case, natural nitrate contents are
low, which makes it easier to detect nitrate groundwater pollution.
INSTITUTIONAL CONSTRAINTS. Little or no monitoring has been done
by regulatory agencies, thus there was a lack of supplementary data, par-
ticularly on waste dischargers. Most polluters had an ingrained belief
that they were not polluters. Thus they tended to hesitate to sample or per-
mit sampling. In addition, in the literature reviewed, the researchers
often represent some interest, such as agriculture, and bias is sometimes
evident. Thus the literature is confusing with regard to effects of specific
pollutants on groundwater.
Description of Alternative Monitoring Programs
Additional monitoring would have been possible without the two major
constraints of time and funding. If more money had been available, the
following could have been done:
Sampling of nitrate in soil moisture and the vadose zone
in septic tank areas, as well as near some point sources
Measurement of water movement in the vadose zone beneath
point sources
More detailed sampling of waste at the land surface, including
determinations of viruses, stable organics, nitrogen forms,
chloride, boron, and trace metals
Test well drilling near some point sources, such as wineries
and meat packing plants, where no nearby wells existed
Possibly, use of stable nitrogen isotopes to differentiate
among sources of groundwater nitrate
More complete chemical analyses of groundwater, as many
existing analyses were incomplete.
If more time was available, the following could have been done:
Establishment of seasonal trends in groundwater nitrate in
more detail
Evaluation of minor sources, such as lawn fertilizers
Statistical correlation of septic tank density and groundwater
nitrate content
Calculation of water budgets and nitrogen budgets for various
sources, including determination of evapotranspiration, perco-
lation, denitrification, crop uptake, and other factors.
40
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Strengths and Weaknesses of Monitoring Program
The major strengths of the investigation were the development of a de-
tailed hydro geologic framework in the area and the comprehensive use of
water well sampling. The selection of high capacity wells for water sam-
pling and chemical analyses permitted evaluation of regional groundwater
conditions. Historical records compiled during the investigation permitted
development of long-term time trends in groundwater nitrate related to
nitrogen sources at the land surface. Other constituents, such as chloride,
proved to be strong tools in determination of possible sources of nitrate.
The thorough literature study preceding the field work was invaluable.
Many of the weaknesses of the investigation were due to the limited ex-
perience of the investigator, as well as time and funding constraints. Some
sources were ruled out or considered negligible without acquisition of data
to support such a decision. Leaking sewers and lawn fertilizers should
have been analyzed in more detail. Insufficient consideration was given to
soils and the vadose zone. Too large an area was selected for study, and
the Fresno sewage treatment plant and the agricultural area southwest of
Fresno should have been studied separately. Reliable chemical analyses
were unavailable for some pollution sources, and data on plant operation
were lacking.
Description of Optimal Monitoring Program
An optimal monitoring program would have included the following:
More land surface or source monitoring, specifically waste
water sampling
Test well drilling at selected point sources of pollution
The Fresno sewage treatment plant should have been studied
separately from the rest of the FCMA
Sampling in the topsoil and the vadose zone, specifically
measurement of the movement of percolating water and
nitrate and chloride contents.
Most of the additional types of monitoring would be costly. The least
costly would be more monitoring at the land surface. Sampling in the va-
dose zone would probably have to be limited to a reconnaissance level,
especially for diffuse sources. The existence of a monitoring program by
regulatory agencies for waste waters and other potential sources of ground-
water pollution would have greatly enhanced the study.
41
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SECTION III
SITE-SPECIFIC GROUNDWATER
QUALITY MONITORING EXAMPLES
Four potential categories of groundwater pollution have been selected to
illustrate application of the major steps in development of the groundwater
pollution monitoring methodology for site-specific conditions agricultural
return flow, septic tanks, percolation ponds, and landfills. Agricultural re-
turn flow represents one of the major potential sources of groundwater pollu-
tion in the western United States. Septic tanks are known to be a major
source of groundwater pollution in some suburban areas. Both of these
sources are generally diffuse, and thus monitoring programs for the two
have certain similarities. Disposal and storage of various types of liquid
wastes in ponds or pits subject to percolation represent another major po-
tential source of groundwater pollution. Landfills for disposal of solid
wastes can be major sources of groundwater pollution in humid areas. Per-
colation ponds and landfills are both point sources and thus monitoring pro-
grams for the two have certain similarities.
After discussion of the salient aspects of monitoring each type of pollu-
tion source, an example illustrating the procedure for selecting site-specific
monitoring alternatives and estimating associated costs is presented. Steps
1, 10, 14, and 15 of the methodology which relate to areawide aspects in
application of the methodology are not included in the discussions.
AGRICULTURAL RETURN FLOW
The area selected to monitor return flow depends primarily on soil con-
ditions, the type of crops irrigated, irrigation methods, farming practice,
and groundwater characteristics. In most cases, large farms (hundreds to
thousands of acres) and irrigation districts (tens to hundreds of thousands
of acres) would be areas of suitable sizes for monitoring.
Nonquality parameters to be monitored include volumes of applied water,
precipitation, recharge from other pollution sources in the area, evapo-
transpiration, and infiltration of excess applied irrigation water. Quality-
related parameters include the quality of applied water, amounts of addi-
tives such as fertilizers and pesticides, concentration due to evapotrans-
piration, dissolution and precipitation reactions in the soil-groundwater
system, crop uptake of some constituents from the irrigation water, and
quality of percolated water. Sampling is usually necessary for the applied
water, percolate in the vadose zone, and groundwater.
42
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Land Surface Monitoring
Land surface monitoring encompasses an inventory of volumes of water
applied to the land surface and other sources of recharge, such as seepage
from streams or canals. Evapotranspiration and rainfall rates must oc-
casionally be measured in the field, but can often be extrapolated from
nearby areas. Compilation of these data in conjunction with runoff deter-
minations will allow calculation of infiltration rates. Amounts of additives
must be inventoried, including fertilizers, soil amendments, and pesticides.
Some of these are directly introduced to the irrigation water, whereas
others are applied on the land. Estimates for application rates per unit
area should be compiled. The chemical quality of applied water must be
known or sampling and analysis undertaken. The approximate volumes and
quality of other sources of recharge must also be determined. In some ir-
rigated areas of the western United States, preliminary inventories of most
of these items have been made for large areas such as irrigation districts.
Vadose Zone Monitoring
Monitoring in the vadose zone includes laboratory and field tests for de-
termination of percolate quality and determination of storage capacity and
travel times for water and specific pollutants in the vadose zone. The oc-
currence of restricting layers in the topsoil and relatively impermeable
strata above the water table should be ascertained. Native soil and geolog-
ical materials may be sampled for determinations such as nitrogen and
total dissolved solids. Because return flow is a diffuse source, detailed
sampling of percolating water in the vadose zone is impractical over large
areas. The major disadvantage of sampling in the vadose zone in the case
of a diffuse source of large areal extent is the cost of obtaining a sample
representative of the entire system. To compensate for this, selected
target areas can be chosen as typical of the larger area. Neutron probe
and tensiometer measurements are the most effective method to trace
water movement, and water samples can be effectively collected from soil-
water samplers in the vadose zone or from wells in the saturated zone. In
most cases analytical determination would be limited to the major inorganic
chemical constituents, nitrogen forms, and boron. Pesticides, phosphorus,
chloride, and potassium could be important in some areas. Sampling fre-
quency in part depends on travel time in the vadose zone. Calculation or
determination of travel time can be made based on infiltration rates and
storage capacity of the vadose zone. If wells are drilled to penetrate the
entire vadose zone and travel time of percolate to the water table is suf-
ficiently slow, sampling during drilling and once every 5 or 10 years
thereafter may be sufficient. Where travel times are less than 1 or 2
years, semiannual sampling may be necessary. Where pressure-vacuum
soil-water samplers are installed as permanent sampling points, monthly
sampling may be done; however, this usually will be unnecessary.
43
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Saturated Zone Monitoring
Monitoring beneath a diffuse source in the zone of saturation should
usually focus on sampling existing wells after long-term pumping. Large-
capacity wells should be selected in order to provide an integrated sample
of the water quality in the area of the well. In areas with few wells, con-
struction of monitor wells may be necessary. Open-bottom cased wells
drilled by the cable-tool method in unconsolidated materials may provide
the most suitable results. Such wells produce water from well-defined
depth zones. Where large seasonal variations in groundwater quality occur,
seasonal trends must be established (based on at least monthly measure-
ments to represent the extremes of chemical quality). Thereafter a semi-
annual or annual sampling program will usually suffice. Long-term chemi-
cal hydrographs can then be plotted to illustrate groundwater quality changes
due to return flow. Often, detection of meaningful changes requires chemi-
cal analyses for a period of a decade or longer.
An analysis for the major inorganic chemical constituents is advisable in
most cases. Total dissolved solids, boron, sodium percentage, nitrate,
and hardness are the major concern. Selected pesticides also should be
periodically determined. The wells to be sampled should be chosen to re-
flect the quality of water in the upper part of the aquifer where pollution
from return flow will first become apparent.
AGRICULTURAL RETURN FLOW EXAMPLE
Step 2 Identify Pollution Sources, Causes,
and Methods of Waste Disposal
For this example, a 50, 000-acre irrigation district in Central California
is given as the area in need of monitoring. The source is given as return
flow. The area is rural with two towns of population less than 500 each.
The area has been intensively farmed for over 80 years. In this case there
is no specific method of waste disposal, as groundwater pollution can result
from normal crop irrigation.
Step 3 Identify Potential Pollutants
The chemical quality of irrigation water is known from records of State
water agencies. Farmers, farm advisors, manufacturers, and regulatory
agencies provide information on application rates of fertilizers, soil amend-
ments, and pesticides. The primary fertilizer elements are nitrogen and
phosphorus. The major soil amendment is gypsum and is widely used in
only two of the subareas. There are five major types of pesticides in use,
including two chlorinated hydrocarbons. The use of pesticides is related
primarily to cropping patterns. Two of these pesticides are applied entirely
in one subarea because of cropping patterns.
44
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Step 4 Define Groundwater Usage
In this district, 95 percent of the ground-water use is for irrigation of
agricultural lands. The remainder is used for domestic purposes in small
communities and rural areas. Despite the fact that the water used for do-
mestic purposes is only a small portion of the total water use, groundwater
provides the sole source of drinking water in the area.
Step 5 Define Hydrogeologic Situation
Subsurface materials are alluvial sediments comprised of interbedded
sand, silt, and clay layers. The depth to groundwater ranges from 50 to
200 feet below land surface and the average annual rainfall is 10 inches.
Irrigation water is supplied from an extensive system of canals, utilizing
surface runoff from nearby areas, and groundwater. Soils range from
highly permeable sandy soils developed on sand dunes to low permeability
hardpans. The regional direction of groundwater movement is westward
through the district toward pumping depressions. Aquifer transmissivities
range from 100,000 to 300,000 gpd/ft and irrigation well yields range from
500 to 1, 000 gpm.
Preliminary investigation includes calculation of an approximate hydrol-
ogic water budget. Surface water inflow and outflow are large items,
whereas groundwater inflow and outflow are small items. Data on precipi-
tation and evapotranspiration can be combined with data on the foregoing
parameters to compute the water budget. The budget indicates whether
there is an imbalance between groundwater recharge and discharge. This
in turn indicates whether groundwater levels are relatively constant, rising,
or falling. This information is pertinent to the monitoring effort, as the
thickness of the vadose zone may vary substantially seasonally and over a
period of years or decades. Sources of recharge are seepage from streams
and canals, return flow of excess applied irrigation water, and groundwater
inflow. Groundwater discharge is primarily through pumping and natural
groundwater outflow. Domestic waste disposal volumes are negligible com-
pared to agricultural return flow volumes.
Step 6 Study Existing Groundwater Quality
Maps prepared based on existing chemical analyses indicate the areal
distribution of total dissolved solids, nitrate, and sodium percentage in the
groundwater. High values of these parameters are generally related to
soil type, cropping and irrigation patterns, and duration of irrigation.
Water quality records indicate high total dissolved solids and nitrate con-
tents in the upper 50 feet of the groundwater body, with much lower con-
tents at deeper intervals. Previous studies by the United States Geological
Survey indicate the chemical quality of sources of recharge other than re-
turn flow.
45
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At this point, available information indicates the advisability of subdivid-
ing the study area. As a result, the study area is divided into five subareas
for the following reasons:
Surface water in the district is supplied from two separate
sources of differing quality
Soils in the district can be categorized into several groups
on the basis of permeability
Irrigation methods vary from place to place, but sprinkler
irrigation is predominant in some areas and furrow irrigation
in others
Fertilizers, soil amendments, and pesticides are applied at
different rates in various portions of the district
Characteristics of the groundwater basin vary, especially
from east to west.
Each subarea has a unique combination of these factors, and thus lends
itself to a separate determination of water budgets and salt balance.
Step 7 Evaluate Infiltration Potential
of Wastes at the Land Surface
Determination of the volume of return flow escaping the root zone is the
objective of this step. Average applied water volumes per acre for the dis-
trict are available from a State water agency. Knowlege of the soils, irri-
gation methods, and cropping patterns enables more accurate estimates to
be made for each subarea. Estimates of canal seepage are available from
the irrigation district and streamflow seepage is known from streamflow
records at various gaging stations operated by the United States Geological
Survey. Crop surveys by District personnel and evapotranspiration rates
from lysimeter tests at a local agricultural experiment station can be used
to determine crop evapotranspiration. Precipitation is measured at several
stations in the District. Average annual return flow is calculated for each
subarea.
Step 8 Evaluate Mobility of Pollutants
from the Land Surface to the Water Table
Travel time of return flow to the water table is generally unknown. How-
ever, preliminary calculations indicate that in cases of shallow water tables,
this travel time would generally range from 6 months to 5 or 10 years. In
cases of deep water tables, the travel time could range from 5 to 50 years.
Application rates of irrigation water are the primary controlling factor.
46
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Because of the pollutant attenuation characteristics of soils and alluvial
deposits in the District, forms of fertilizer such as phosphorus and potas-
sium would be adsorbed by soils and geologic materials. The primary
form of nitrogen fertilizer is anhydrous ammonia. Ammonia tends to be
sorbed to materials in the vadose zone. However, oxidizing conditions in
the vadose zone permit formation of nitrate which is subsequently leached
to the groundwater. The gypsum contains sulfate which is fairly mobile in
the vadose zone. Although calcium may be adsorbed in the vadose zone, it
may subsequently be replaced by other cations and reach the water table.
Some precipitation of gypsum may occur in the vadose zone. Tests at agri-
cultural experiment stations indicate that only one of the pesticides used is
subject to significant leaching; however, its mobility in the vadose zone is
unknown.
Step 9 Evaluate Attenuation of Pollutants
in the Saturated Zone
Horizontal movement of pollutants in the aquifer is not of primary con-
cern, in this example, as a diffuse source is being considered. However,
the extent of return flow in the aquifer in a vertical sense needs to be ap-
proximated. This is necessary in order to effectively utilize existing wells
for monitoring purposes. Wells that are perforated too deep may not indi-
cate any effect of return flow. Return flow tends to occur in the upper 50
to 100 feet of the aquifer, as shown by existing well data and chemical
analyses. This occurrence is largely due to the layered nature of the al-
luvium which results in small vertical permeabilities compared to horizon-
tal permeabilities.
Step 11 Evaluate Existing Monitoring Programs
A brief investigation of the records of the local water resource agencies
indicates that there are no existing monitoring programs for groundwater
quality in the area except for limited sampling of domestic wells in the two
towns.
Step 12 Establish Alternative
Monitoring Approaches
Analysis of the hydrogeologic framework, groundwater quality, and ir-
rigation practice of the district indicates that monitoring at the land surface,
in the vadose zone, and in the saturated zone is necessary. Monitoring in
the vadose zone is where the test drilling and relatively expensive and
time-consuming aspects of monitoring come into play. The cost of moni-
toring in the vadose zone depends highly on the density of sampling devices.
47
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LAND SURFACE MONITORING. This phase of the monitoring program
was previously developed largely in Steps 3 and 7. This monitoring will be
continuously updated approximately every 5 years. No additional sampling
or analysis will be necessary.
VADOSE ZONE MONITORING. One site in the District is selected for
detailed monitoring of percolate in the vadose zone. This monitoring is
necessary due to the virtual absence of such data in the project area. The
site is 40 acres in size. Soils, irrigation methods, and cropping patterns
are judged typical of the larger area. Primary costs of this phase are for
well construction, installation of sampling devices, sample retrieval, and
chemical analyses and interpretation.
Three alternatives have been selected for monitoring in the vadose zone.
The most effective means of sampling and analysis are derived from
Everett et al. (1976). Alternative A has two access wells for neutron
probes and three holes for pressure-vacuum soil-water sampler nests
(Everett et al. , 1976, Figure 15). Alternative B has five access wells for
neutron probes and ten holes for pressure-vacuum soil-water sampler nests.
Alternative C has ten access wells for neutron probes and 20 holes for
pressure-vacuum soil-water sampler nests. The access wells for neutron
probes are 2 inches in diameter and 150 feet deep. Three pressure-vacuum
soil-water samplers are placed at 10-, 25-, and 50-foot depths in a 6-inch
diameter hole to comprise each nest.
Neutron probe analysis and lysimeter sampling are carried out on a
monthly basis. The percolate is analyzed for the major chemical constit-
uents and boron. For Alternatives A, B, and C, the number of percolate
samples collected monthly are 9, 30, and 60, respectively. Vadose zone
monitoring is envisioned to be unnecessary after the first 2 years, because
this period is believed to be sufficient for determination of rates of water
movement and pollutant attenuation.
SATURATED ZONE MONITORING. Due to their large number, existing
wells are determined to be sufficient for sampling. A carefully conducted
well-data collection procedure is necessary before wells are selected for
monitoring. Seasonal variations in well-water quality in the district are
generally unknown. A 2-year period is chosen for bimonthly sampling of
300 large-capacity wells. Thereafter a semiannual sampling program is
selected for 50 wells chosen from the 300. The major inorganic chemical
constituents and boron are determined for the well-water samples. Pri-
mary costs of this phase are for sample collection, chemical analysis, and
interpretation of results.
48
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Step 13 Select and Implement the
Monitoring Program
Given the alternatives from Step 12, costs are derived based on a com-
panion report (Everett et al. , 1976).
LAND SURFACE MONITORING. It is estimated that a person with a
B. S. degree in hydrogeology or water resources engineering and a mini-
mum of 2 years of work experience in groundwater (salary $12, 000 per
year) could collect most of the data required on surface water, ground-
water, soils, climatology, and waste loads in about 2 months. Costs for
the time of the junior-level individual are calculated by applying a multi-
plier of 2. 5 times the salary. A senior-level hydrogeologist, one with an
M. S. degree in hydrogeology and a minimum of 5 years of work experience
(salary $18,000 per year) in groundwater, could supervise the monitoring
effort. About 1 month of his time would be necessary to review and inter-
pret collected data, interpret hydrogeologic conditions with respect to
groundwater pollution, delineate subdivisions of the study area, and to es-
tablish monitoring alternatives. Costs for the time of the senior-level in-
dividual are also calculated by applying a multiplier of 2. 5 times the salary.
This phase is primarily a one-time effort, but might have to be periodically
updated, depending on future land use, irrigation methods, fertilizer appli-
cation rates, and other factors. Costs for this phase of the program would
be $5, 000 for the junior-level individual's time and $3, 750 for the senior-
level individual's time, or about $8, 750. It is estimated that $2, 000 per
year would cover periodic updating of this phase every 3 or 4 years if nec-
essary.
VADOSE ZONE MONITORING. Costs for access wells for the neutron
probe and for soil-water sampler wells are taken from Everett et al. (1976,
Figure 18). However, in this case, slightly different well-construction
techniques are necessary. Casing is not necessary, but special plugs must
be installed to separate the three samplers in each hole. Reasonable esti-
mates can be derived from Everett et al. (1976, Figure 18).
TABLE 1. WELL-CONSTRUCTION COSTS FOR VADOSE ZONE MONITORING
Type of Well
Access Well Construction
(including casing and development)
Soil-water Sampler Well Construction
(including sampler installation)
TOTAL
A
500
500
1,000
Alternatives
(cost in dollars)
B
1,100
1,750
2,850
C
2,100
3,380
5,480
49
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In addition, logging test holes and supervision of sampling device instal-
lation by the junior-level individual would require 1 month for Case A, 3
months for Case B, and 6 months for Case C. The costs of his time for
these alternatives are $2,500, $7,500, and $15,000, respectively.
One neutron probe device with 200 feet of cable is purchased for $3, 000
(Everett et al. , 1976, p 36). Each soil-water sampler costs $20 and one
hand-pump service kit costs $30. Including tubing, the samplers required
for each hole cost $70. Only one service kit is needed for all of the sampler
wells.
The moisture logging cost per run per well for Alternative A, with a
density of one per 20 acres, is approximately $250 using the cost curve of
one per acre density (Everett et al. , 1976, Figure 9), totaling $500 for the
40-acre tract. Since this cost curve was prepared for point-source applica-
tion, densities in this example are too low to use the graph directly, and
costs must be estimated by extrapolation. The cost per run per well for Al-
ternative B, with a density of one per 8 acres, would be approximately $225.
The cost per run per well for Alternative C, with a density of one per 4 acres,
would be approximately $200 or $2, 000 total. The monthly time for the
junior-level individual for sampling soil-water samplers is 0. 5 day for Al-
ternative A, 1.5 days for Alternative B, and 2.5 days for Alternative C.
The chemical analyses for percolate obtained from the soil-water sam-
plers include the major inorganic chemical constituents (Everett et al. ,
1976, p 114) and boron (Everett et al. , 1976, Table 14). The cost of analy-
sis of percolate for the major inorganic chemical constituents is $12 per
sample and the cost for boron (dissolved) is $10. For purposes of this
example, a special group rate of $17 is assumed for a combination of the
foregoing. Discounts of 10 percent are applied for total cost over $500 and
20 percent for total cost over $1,000 (Everett et al. , 1976, p 113). Analyt-
ical costs are $17 per water sample for Alternative A, $15 per sample for
Alternative B, and $13. 50 per sample for Alternative C. The costs for
vadose zone monitoring are given in Table 2.
In order to select the most cost-effective alternative, consideration is
given to impacts of pollution on groundwater use. Nitrate and pesticides
pose a potential health effect on groundwater used for drinking purposes.
No feasible alternative water-supply sources for drinking water are avail-
able. Pollution due to return flow also creates economic impacts, as even-
tually the degraded groundwater can result in decreased crop yields in the
District. Assessment of long-term damages is not possible. Another con-
sideration is the net worth of the farm produce. A final consideration is the
money available for monitoring in the district and other districts in the re-
gion. Consideration of all these factors leads to selection of Alternative B.
50
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TABLE 2. COSTS FOR VADOSE ZONE MONITORING
Alternatives
(cost in dollars)
One -Time Costs
Well Construction and Logging
Neutron Probe and Soil -water Samplers
TOTAL
Annual Costs (first two years only)
Neutron Moisture Logging
Soil -water Sampling
Chemical Analyses
TOTAL
A
3,500
3,240
6,740
6,000
700
1,840
8,540
B
10,350
3,730
14,080
13,500
2,100
5,400
21,000
C
20,480
4,430
24,910
24,000
3,500
9,720
37,220
SATURATED ZONE MONITORING. The junior-level individual would
spend one month in collecting existing well data and groundwater quality
data. Ten days would be spent collecting water samples from wells for
each round during the first 2 years. Five additional days would be spent
by this individual checking chemical analyses and tabulating the results
for each round. First-year costs would be $13,750 and second-year costs
would be $11,250. The senior-level individual would spend 2 weeks each
year for supervision and review of the program. Costs would be about
$1, 880 each year. A routine irrigation water analysis would be $17 per
sample, as calculated previously for analyses of percolate in the vadose
zone. For groups of 300 samples, the analytical cost per sample is
lowered to $13.50. For the first year, personnel costs would be $15,630
and chemical analyses $24,300. For the second year, personnel costs
would be $13, 130 and chemical analyses $24, 300.
After the first two years, the junior-level individual would spend 2 days
collecting samples for each round, and 1 additional day checking chemical
analyses and tabulating results for each round. Costs for his time would
be $630 per year. Supervision and review by the senior-level individual
would be about 1 week each year after the first 2 years, at a cost of $940
per year. For groups of 50 water samples, the analytical cost per sample
is $15. For each year after the first two, personnel costs are $1,570 and
chemical analyses $1,500.
SUMMARY. Table 3 summarizes costs for the entire program.
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TABLE 3. TOTAL COSTS FOR AGRICULTURAL RETURN FLOW MONITORING
Type of Monitoring
Land Surface
Vadose Zone
Saturated Zone
TOTAL
Year 1
8,750
35, 080
39, 930
83, 760
Annual Costs
Year 2
2,000
21,000
37,430
60,430
(dollars)
Subsequent
Years
2,000
0
3,070
5,070
These costs reflect several factors. The greatest costs are incurred
during the first 2 years of the monitoring program. One-time costs make
the first-year costs almost 40 percent greater than second-year costs. An-
nual costs after the intensive 2-year monitoring period are only about 10
percent of the average annual cost during the first 2 years.
SEPTIC TANKS
The area selected to monitor depends primarily on the location and con-
figuration of unsewered areas. In general, septic tanks in sparsely popu-
lated rural areas are insignificant sources of groundwater pollution. In
more densely populated areas, soil conditions, septic tank density, method
of disposal, and groundwater characteristics influence the selection of the
area to be monitored. The area should be chosen to insure uniformity of as
many of these factors as possible. Downgradient areas within 1 mile of the
unsewered area should also be included to monitor movement of recharged
septic tank effluent. The area selected typically ranges from several hun-
dred to several thousand acres in size.
Nonquality factors to be considered include volume of the septic tank ef-
fluent, method of effluent disposal, and soil hydraulic characteristics.
Septic tank density, or lot size, is an important factor. Disposal methods
range from shallow drainfields where substantial losses due to evapotrans-
piration occur to seepage pits where this loss is insignificant. Usually the
disposal methods are selected on the basis of soil conditions. Percolation
rates and the presence of restricting layers influence the impact of septic
tank effluent on groundwater quality. Quality-related factors include the
quality of septic tank effluent and percolate in the vadose zone. The major
sampling required is for effluent, percolate, and shallow groundwater.
Soils and geologic materials may be occasionally sampled to determine pol-
lutant attenuation mechanisms, such as adsorption.
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Land Surface Monitoring
The most effective type of land-surface monitoring comprises inventoring
septic tank densities, volumes of septic tank effluent, water use, and pos-
sibly determining a water budget for the area. Data on septic tank densities
and volume of septic tank effluent can be determined, for residential areas,
from lot sizes in unsewered areas. Special attention should be focused on
schools, shopping centers, and other facilities with effluent volumes signif-
icantly greater than those for individual households. The volume of effluent
has been carefully documented in some areas. Figures for in-home water
use are available for most areas. The water subject to septic tank disposal
is used in the home for toilets, sinks, garbage disposers, bathtubs, show-
ers, dishwashers, washing machines, and water softeners. In areas -where
little or no data have been developed, representative households can be
chosen for detailed monitoring. The effluent should be characterized as to
quality, especially for total dissolved solids and total nitrogen. Sampling
of representative effluent may be necessary. The inventory should include
pertinent data on the types of detergents used and the extent of the use of
water-softening devices.
In the case of shallow disposal, such as seepage trenches, water budget
analyses may be necessary in order to determine infiltration of septic ef-
fluent. Precipitation and evapotranspiration can be estimated from records
in the area. However, judgment is necessary to calculate infiltration, as
some seepage trenches may be below the root zones of most plants. In
other cases plant uptake of nutrients, such as nitrogen, from the effluent
could be significant.
Vadose Zone Monitoring
Determination of storage capacity and travel time for water and specific
pollutants in the vadose zone is an important component of the monitoring
program. Delineation of restricting layers in the topsoil and relatively
impermeable geologic materials above the water table is important. Lab-
oratory and field tests can be conducted to determine the quality changes
of effluent during percolation through native soil and geologic materials.
Sampling of soil and geologic materials for nitrogen determinations may
be necessary where natural sources of nitrogen are present. Because sep-
tic tank effluent is a diffuse source over a monitoring area, detailed sam-
pling of percolating water in the vadose zone is impractical in most cases.
However, monitoring areas are generally of a size such that several holes
could be drilled for sampling in each area.
Neutron probes and tensiometer measurements can be effectively used
to trace water movement. Percolate samples can be collected from soil-
water samplers in the vadose zone or from wells in the saturated zone.
In most cases, analyses of percolate samples are limited to the major
53
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inorganic chemical constituents and nitrogen forms. BorcTn, detergents,
stable organics, and bacteriological constituents could be important in some
cases. The frequency of sampling depends on travel time in the vadose zone.
For wells penetrating the entire vadose zone, and when travel times are
very slow, sampling may be necessary only once every few years. How-
ever, percolate should be collected from the soil-water samplers generally
on a monthly basis. Percolation rates of septic tank effluent often are in
the range of 1 to 2 feet per acre per year.
Saturated Zone Monitoring
As septic tanks represent a diffuse source, effective monitoring in the
saturated zone usually entails sampling of existing wells after long-term
pumping. These wells should be large-capacity wells, if possible, in order
to provide an integrated sample. Such wells are often present in urban or
suburban areas. Shallow wells should be selected which tap the upper part
of the aquifer; an occasional deep well should be included. Seasonal trends
should be established in some areas, and a semiannual sampling program
will usually suffice thereafter. The establishment of seasonal trends may
require monthly sampling for several years. Wells to be sampled include
not only those beneath septic tank areas, but upgradient and downgradient
wells. Upgradient sampling can provide an indication of water quality un-
affected by septic tank effluent. Downgradient sampling indicates the down-
gradient movement of septic tank effluent in the aquifer. Usually a distance
of 1/2 mile or so from the downgradient boundary of the unsewered area
will be adequate. This limit is due to pollutant attenuation mechanisms in
the saturated zone. Chemical hydrographs can then be plotted to illustrate
long-term trends in groundwater quality. Many years of records may be
necessary for proper interpretation.
Analysis of well water for the major inorganic chemical constituents is
advisable in most cases. Total dissolved solids, nitrate, chloride, and
possibly other nitrogen forms are of chief concern. Detergents, boron,
hardness, stable organics, and bacteriological constituents may also be
important.
SEPTIC TANK EXAMPLE
Step 2 Identify Pollution Sources, Causes,
and Methods of Waste Disposal
In this example, a 2, 000-acre suburban area in an alluvial basin of Cen-
tral California is given as the area for monitoring of septic tank effluent.
Septic tank treatment and disposal has been practiced in the area for about
30 years. The area to be monitored includes upgradient and downgradient
areas within 1 mile of the unsewered area.
54
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A portion of the water pumped in the area is returned to the groundwater
by lawn irrigation return flow and septic tank effluent disposal systems.
The method of septic tank effluent disposal used is rather uniform over the
area; seepage fields are used that are generally 8 to 10 feet below the land
surface. Several schools and small shopping centers are points of heavy
effluent discharge, whereas the remainder of the area is residential. Fer-
tilizers used for lawns, gardens, trees, and shrubs may contribute to
groundwater pollution. Urban runoff is diverted from the area by storm
drains and disposed of elsewhere.
Step 3 Identify Potential Pollutants
Well water in the area averages about 250 ppm total dissolved solids.
Based on analyses of domestic sewage effluent from nearby sewered areas,
the dissolved solids content of the septic tank effluent is estimated at 500
ppm. There is no water softening in the area. Chlorides averaging 80 ppm
are present in sewage effluent discharged from nearby areas. Boron is
introduced through the use of detergents and fluoride is added for health
reasons at the well sites. Boron, fluoride, and total nitrogen concentrations
in the septic tank effluent are estimated at 0.5, 1. 2, and 25 ppm, respec-
tively, based on data in the literature.
Step 4 Define Groundwater Usage
Groundwater is pumped for municipal use, which includes domestic use
and lawn irrigation. One hundred percent of the use is for municipal use,
of which about 25 percent is for in-house use (including drinking water),
and about 50 percent is for yard irrigation. The remainder is used for
cooling purposes (15 percent) and commercial use (10 percent). Additional
information on water use is presented in Step 5.
Step 5 Define Hydrogeologic Situation
The depth to groundwater ranges from 50 to 70 feet, and no perched
water is present in the alluvium. The soils are uniform over the area and
no restricting layers are present. Water is supplied entirely by ground-
water. The aquifer transmissivity is 100,000 gpd/ft, and the water level
slopes uniformly to the south. Well yields range from 500 to 1,000 gpm
and well depths range from 100 to 200 feet. Wells have usually been drilled
by the cable tool method and casings are perforated over short intervals or
are unperforated (open-bottomed).
Groundwater recharge is primarily from groundwater inflow and the
quality of this water is determined primarily by natural factors. Available
studies indicate that this water is of the calcium-sodium bicarbonate type
with total dissolved solids content less than 200 ppm. Groundwater dis-
charge is by well-pumping and groundwater outflow. Water levels are rel-
atively stable from year-to-year, although they fluctuate seasonally.
33
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Step 6 Study Existing Groundwater Quality
Maps have been previously prepared by County agencies based on existing
chemical analyses. These maps indicate the areal distribution of total dis-
solved solids, chloride, nitrate, and hardness in the groundwater. High
values are generally found in the central portion of the study area. Chemi-
cal analyses of water from shallow wells in the area indicate higher total
dissolved solids, nitrate, and chloride contents than groundwater beneath
surrounding areas. Deep wells produce water of a chemical quality similar
to that in the surrounding area.
Step 7 Evaluate Infiltration Potential
of Wastes at the Land Surface
Calculation of the volume of septic tank effluent percolating below septic
system leach lines is the objective of this step. Daily water consumption
is available from the water purveyor, since well pumpage and household use
are metered. Lawn irrigation is a major use in the summer, but minor in
the winter. Based on literature studies and a comparison of water usage in
the summer and winter, domestic use subject to septic tank treatment and
disposal is calculated. The number and size of lots are available from the
County public works department. There are 3, 900 lots in the residential
portion of the study area (1, 850 acres) and the population therein is 8, 900.
The average water use in the residential area is 300 gallons per capita
per day and the average effluent volume is 75 gallons per capita per day.
The total volume of septic tank effluent in the residential area is about
670, 000 gallons per day, or 750 acre-feet per year. This averages about
14 inches annually over the part of the residential area not occupied by
streets or structures (650 acres). Two schools and two shopping centers
are located on a total of about 150 acres within the study area. Annual
water use for the schools and shopping centers averages about 90, 000 gal-
lons per day. The effluent volume from these four sources averages
100, 000 gallons per day during the school year and 20, 000 gallons per day
during the rest of the year. As the septic tank effluent is disposed of be-
low the root zone of most plants, no loss of effluent to evapotranspiration
is assumed; thus no water budget analysis is necessary.
On the basis of winter and summer use, evapotranspiration rates, and
irrigation methods, it is estimated that return flow from irrigation averages
1. 0 million gallons per day, or about 21 inches per year over the irrigated
part of the residential area (650 acres).
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Step 8 Evaluate Mobility of Pollutants
from the Land Surface to the Water Table
Previous studies have been undertaken at a nearby Agricultural Research
Service site and at the local university. These studies have generally docu-
mented travel times of septic tank effluent to the water table and have eval-
uated the movement of nitrate in the vadose zone. Travel times where ef-
fluent application rates are 14 inches per year and the water table is 50 feet
deep are about 5 years. Little denitrification occurs because of the aerobic
conditions prevailing in the vadose zone and the lack of organic matter.
Hence, nitrogen forms in the effluent are oxidized to nitrate and leached to
the water table. Bacteriological constituents, including viruses, are re-
moved within several feet of travel in the alluvium above the water table.
Phosphorus is strongly retained in the vadose zone due to sorption and
chemical precipitation.
For return flow from irrigation, travel times to the water table are
comparable to that discussed above. Nitrogen behaves similarly as in the
case of septic tank effluent.
Step 9 Evaluate Attenuation of Pollutants
in the Saturated Zone
This step is necessary in order to determine the extent of downgradient
monitoring needed. In this case inspection of the maps prepared for well-
water quality indicates no detectable effects occur more than 1/2 mile
downgradient of the unsewered area after 30 years of operation. The extent
of septic tank effluent in the aquifer in a vertical sense also needs to be
estimated. This is necessary in order to effectively utilize existing wells
for monitoring purposes. In general septic tank effluent tends to occur in
the upper 50 feet of the aquifer, as shown by existing well data and chemical
analyses.
Step 11 Evaluate Existing Monitoring Programs
Fairly comprehensive monitoring programs are in effect for all wells for
the major chemical constituents (including nitrate, fluoride, and total dis-
solved solids). One laboratory provides all of the analytical services and
the chemical analyses appear to be adequate for monitoring groundwater
pollution. No determination for detergents or stable organics has been
made. Bacteriological sampling is routinely performed by the water pur-
veyor and analyses for fecal coliform are consistently negative.
Step 12 Establish Alternative Monitoring Approaches
Analysis of alternative monitoring programs in relation to the hydrogeo-
logic framework, groundwater quality, and waste disposal practice
57
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indicates that no vadose zone monitoring is necessary. Routine land surface
monitoring and sampling of large-capacity wells can be used to effectively
monitor the source. The most cost-effective alternative is selected after
consideration of the impact of septic tank effluent on water use in the area
and downgradient areas. Nitrate and stable organics in groundwater used
for drinking purposes pose a potential health effect. Pollution due to sep-
tic tank effluent can also degrade municipal supplies in a monetary sense,
especially for parameters such as hardness. Water treatment in the home
or by the water purveyor may be necessary to enable the use of the de-
graded water. A final consideration is the funds available for monitoring
in the subdivision and other unsewered areas in the region. Consideration
of all of these factors leads to selection of the most cost-effective method.
LAND SURFACE MONITORING. This phase of the monitoring program
was largely developed in Steps 3 and 7. No annual updating is deemed nec-
essary.
SATURATED ZONE MONITORING. Because the source to be monitored
is generally diffuse and travel times of percolate to the water table are in
terms of about 5 years, long-term monitoring of large-capacity pumping
wells can be effectively used. Previous monthly sampling has established
that peak nitrate concentrations occur in late summer and that the lowest
values occur in early spring. Thus, about 25 wells are selected for con-
tinuous monitoring and chemical analyses are performed on water samples
taken semiannually. Analyses include the major inorganic chemical con-
stituents, boron, and fluoride. Samples are collected annually to deter-
mine the stable organic, detergent, and ammonia contents in water from
six selected wells.
Step 13 Select and Implement the Monitoring Program
The monitoring program was already selected in Step 12 based on ex-
perience and hydrogeologic judgment. The following costs are then derived
from Everett et al. (1976).
LAND SURFACE MONITORING. A person of minimum qualifications
(i. e. , a B. S. degree in hydrogeology or water resources engineering and
2 years working experience) could collect most of the required data on
water use, lot size, septic tank effluent disposal methods, quality of source
water and septic tank effluent, and lawn irrigation and fertilizers in about
1 month. Data on groundwater conditions, well data, and historical chemi-
cal analyses could also be collected during this period. A one-half week
review by a senior individual costs $470. This phase is primarily a one-
time effort. No costs for updating have been calculated for this analysis.
Total cost during the first year of the program would be $2, 970.
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VADOSE ZONE MONITORING. Vadose zone monitoring encompasses
the review of existing reports and consultations with researchers in the
area. The junior-level individual collects these data in 1 week and a
senior-level individual reviews and interprets them in one-half week. This
phase is a one-time effort during the first year and costs $1, 160.
SATURATED ZONE MONITORING. Sampling of water wells is con-
ducted by local agencies at no additional cost. Costs for the major inorganic
chemical constituents are given in Everett et al. (1976, p 114) as $12 per
sample. Costs for boron and fluoride determinations are given in Table 14
of the same reference as $10 each. A special group rate is assumed for
determination of all of these constituents. For the samples collected semi-
annually, determinations of the major inorganic chemical constituents, in-
cluding boron and fluoride, cost $22 per sample, which is discounted to $20
per sample for groups of 25 samples. The annual analytical cost is $1,000
per year. For the samples collected annually, costs per sample are $5 for
ammonia (Everett et al. , 1976, Table 14), $10 for methylene blue active
substances (Everett et al. , 1976, Table 15), and $20 for biochemical oxygen
demand (Everett et al. , 1976, Table 15). A special group rate of $30 per
sample is assumed for these annual determinations, or a total of $180.
Total analytical costs are thus about $1, 180 per year.
Checking chemical analyses and tabulating results requires 1 week each
year for the junior-level individual at a cost of $630. Supervision of the
program and annual review by the senior-level individual requires 1 -week
at a cost of $940. Total annual personnel costs are $1,570.
SUMMARY. Table 4 summarizes costs for the entire program.
TABLE 4. COST SUMMARY FOR MONITORING SEPTIC TANK POLLUTION
Type of Monitoring
Land Surface
Vadose Zone
Saturated Zone
TOTAL
Annual
Year 1
2,970
1,160
2,750
6,880
Cost (dollars)
Subsequent Years
0
0
2,750
2,750
These costs reflect several factors. The annual cost is relatively low
due to the use of existing programs for collecting samples. The overall
program cost is relatively low due to the lack of well drilling and vadose
zone sampling, neither of which are necessary in this example.
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PERCOLATION PONDS AND LINED PONDS
Ponds for containment of liquid wastes are potential point sources of
groundwater pollution. Two major categories of ponds presented in this
discussion are percolation ponds and lined ponds. The first category is
represented by large-scale percolation of sewage effluent to remove bac-
teria and possibly other constituents. In this case large volumes of water
are recharged per acre; for example, in the range of 20 to 100 feet per
year. The second category is represented by disposal or storage of some
oilfield wastes, industrial wastes, and certain toxic materials in lined
ponds. Artificial liners have come into wide use to limit infiltration, and
small amounts of seepage or leakage per acre usually occur (less than 1
inch to several inches or feet per year). The type of monitoring effective
for each category is basically different.
In the case of percolation ponds, water budget evaluation can be effec-
tively used to determine infiltration. Thus nonquality parameters to be
measured include rates of waste discharge, precipitation, and evaporation.
The infiltration can be calculated by measuring inflow to the pond, storage
changes, precipitation, and evaporation.
Artificial liners range from compacted soil or clay to impermeable
plastic and rubber liners. "Seepage" may be termed slow-flow through a
liner over the entire lined area, whereas "leakage" is flow through breaks
or perforations in the liner. Monitoring may be necessary for almost all
ponds despite the lining material. Liners can be pierced or joints not care-
fully sealed during installation. Chemical deterioration is common for
some types of liners exposed to toxic wastes. The water budget approach
usually is not applicable in this case, as the infiltration rate is usually less
than the error inherent in calculating infiltration. Rather, monitoring
focuses on the physical integrity of the liner, reactions between wastes and
the liner, and detection of leaks.
Factors determining percolate quality in both cases include the waste
discharge quality, concentration of pond water by evaporation, dilution of
pond water by precipitation, chemical changes in pond water, and dissolu-
tion and precipitation reactions in the topsoil and vadose zone. Retrieval
of water samples from the waste discharge stream and ponds, percolate in
the vadose zone, and shallow groundwater are the most effective sampling
methods. Topsoil and geologic materials are sampled where significant
retention of some constituents is important.
Land Surface Monitoring
Nonquality monitoring for percolation ponds involves accumulating data
for calculation of the water budget. The waste discharge flow can usually
be measured at the point of entry to the pond. In some ponds recycling
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occurs and outputs must also be measured. Flow meters can often be in-
stalled in discharge pipes, and weirs and flumes can be installed to meas-
ure flow in other cases. Thus a continuous record of waste discharge is
available. For large ponds, evaporation and precipitation may have to be
measured onsite. To a large degree this depends on the climatological
homogeneity of the area. Land pans and floating pans can be used to cal-
culate evaporation from a free-water surface. Extrapolations from nearby
areas can be made over climatologically homogenous areas. Daily meas-
urements enable calculation of infiltration. Radioactive isotopes, such as
tritium, have been used to directly measure seepage rates. Also, stable
hydrogen isotopes are fractionated during evaporation, and thus the deu-
terium content of pond water can indicate the relative percentages of evap-
oration and infiltration.
Water samples can be collected from the discharge stream or the open
pond. Sampling in open ponds may be greatly hampered by netting or other
features designed for wildlife protection. Large fluctuations in discharge
stream quality often occur due to variations in plan operational characteris-
tics. Compositing of samples from the discharge stream is thus necessary.
Continuous recording devices may be used for some parameters such as
electrical conductivity. Sampling open pond-water quality to determine
percolate may be more representative than sampling the waste discharge
stream. Boats may be used or in some cases special walkways constructed
for sample retrieval. Of importance is the collection of a sample that
would be representative of water that would eventually percolate. Certain
parts of large ponds may be much more favorable for infiltration than others
and consideration should be given to this factor when selecting sampling
sites. Sample frequency often must be established on a trial and error
basis. For composite samples, weekly composites of samples collected at
4- to 8-hour intervals is ordinarily sufficient. For pond samples, weekly,
biweekly, or monthly sampling is usually sufficient. The constituents to
be analyzed depend on the type and charcteristics of the waste, as well as
water use in the area.
Vadose Zone Monitoring
Monitoring in the vadose zone beneath percolation ponds is especially
important when percolate travel time from the land surface to the water
table is so long (20 to 30 years or greater) as to render saturated zone
monitoring ineffective. Where substantial retention of toxic pollutants oc-
curs in the vadose zone, it may also be necessary to obtain soil samples
at various depths.
Neutron probes and tensiometers can be used to trace water movement
and pressure-vacuum soil-water samplers can be used for water sample
collection. Laboratory and field tests can be performed to evaluate the
reaction of percolated waste water with soils and geologic materials. For
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example, the sorptive capacity for various trace metals can be determined.
Also, the effect of extreme pH values in percolated waste water on the dis-
solution of minerals in geologic materials can be evaluated.
Appropriate sampling devices can be installed for artificial liners that
may leak. One method is to use two liners separated by a layer of soil and
tile drain pipes. The lower liner is graded toward a central point for sam-
ple collection. Any leakage through the upper liner tends to accumulate on
the lower liner and can be collected. Obviously, the lower liner must be
relatively impermeable and carefully constructed for this method to be ef-
fective. Sampling of nearby wells can also provide information on leakage.
Saturated Zone Monitoring
Resistivity methods can be used where high salinity wastes are ponded
and existing wells are not suitable for monitoring. Specially designed moni-
tor wells tapping the shallow portion of the saturated zone are often neces-
sary. Cable-tool drilled wells that are either unperforated or are perfo-
rated over short intervals may be effective in many cases. A number of
small-diameter observation wells can be effectively sampled periodically
by use of a portable submersible pump. In some cases bailing or air-jetting
may be used for sample retrieval. Consideration should also be given to
sampling one or more large-capacity wells typical of those used in the area.
Such wells may provide data on regional groundwater quality. Once season-
al trends are established, the frequency of sample collection can be deter-
mined. In general, monthly or bimonthly sampling is sufficient. The spe-
cific determinations depend on the composition of the waste water and the
water use in the area.
PERCOLATION POND EXAMPLE
Step 2 Identify Pollution Sources, Causes,
and Methods of Waste Disposal
In this example, a percolation pond for the disposal of toxic industrial
wastes in the eastern United States is the source to be monitored. The
pond has been in operation for 5 years, is 20 acres in size, and about 5
feet deep. The topsoil has been removed to achieve higher infiltration
rates.
Step 3 - Identify Potential Pollutants
The discharged waste is a low pH sodium chloride brine containing some
trace metals. Total dissolved solids commonly exceed 10,000 ppm and
there are high concentrations of arsenic, cadmium, chromium, barium,
and silver. The salinity and trace element content of the -waste discharge
fluctuates considerably due to plant operation. Pond-water quality shows
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less fluctuation due to damping by the storage in the pond. Dilution by pre-
cipitation falling on the water surface also occurs.
Step 4 Define Groundwater Usage
There is no use of groundwater in the immediate area. However,
County-wide plans indicate the probability of urbanization within 20 years.
The future water supply would likely be provided by wells.
Step 5 Define Hydrogeologic Situation
The average annual rainfall is about 50 inches per year, and glacial till
materials about 100 feet thick comprise the aquifer. These aquifer materi-
als are highly permeable and well yields in the region range from 500 to
1, 000 gpm. The aquifer is underlain by relatively impermeable igneous
and metamorphic rocks. Groundwater flow is to the north at a uniform
gradient of about 20 feet per mile. Groundwater flow rates are about 1 foot
per day. The regional depth to water is about 20 feet; however, a mound
is present beneath the pond and groundwater is believed to be less than 10
feet deep. No wells are in the immediate area. Recharge is from precipi-
tation and groundwater discharge is to streams in the area.
Step 6 Study Existing Groundwater Quality
Native groundwater in the region is of excellent chemical quality, with
total dissolved solids less than 50 ppm. Groundwater quality beneath the
percolation pond is unknown.
Step 7 Evaluate Infiltration Potential of Wastes
at the Land Surface
Since no previous measurements are available on which to accurately
calculate infiltration rates, a monitoring program will be established for
this purpose. However, a preliminary evaluation can be made. Regional
data are gathered on precipitation and evaporation from free-water surfaces.
It is estimated from the amount of water used by the industry that about
2, 000 acre-feet per year of waste water is discharged to the pond. A water
budget analysis is used to estimate infiltration. Infiltration is estimated to
be about 1, 950 acre-feet per year, or almost 100 feet per year over each
acre of the pond.
Step 8 Evaluate Mobility of Pollutants
from the Land Surface to the Water Table
There are no significant restricting layers present above the water table
to obstruct downward percolation of recharged waste water. There are no
field data in the region on the mobility of pollutants in this type of waste.
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However, sodium and chloride are generally highly mobile in such situations.
Studies in similar areas also reveal that arsenic, cadmium, and chromium
may be mobile. On the other hand, barium and silver are not expected to be
mobile due to chemical precipitation above the water table.
Step 9 Evaluate Attenuation of Pollutants
in the Saturated Zone
This step is necessary in order to properly determine the location of
monitor wells to be drilled near the percolation pond. Physical factors im-
portant in the analysis for this step are the water budget of the area, slope
of the water table, transmissivity of aquifer materials, and dynamics of
groundwater flow. The most valid data are derived from previous pollution
studies in other areas of similar hydrogeology. Waste plumes for compar-
able hydrogeologic situations and for these waste percolation rates indicate
detectable salinity increases in the aquifer for a distance of only about 1/2
mile downgradient of the source after 20 years of operation.
Step 11 Evaluate Existing Monitoring Programs
There are no existing monitoring programs near this site.
Step 12 Establish Alternative Monitoring Approaches
Analysis of the hydrogeologic framework, waste characteristics, and
disposal method indicates that monitoring at the land surface, in the vadose
zone, and in the saturated zone is necessary. Alternatives are involved
primarily with monitoring in the vadose zone and in the saturated zone.
The most effective methods are chosen from a companion report (Everett
et al. , 1976).
LAND SURFACE MONITORING. Daily precipitation and evaporation
rates are measured onsite by us e of a standard U. S. Weather Bureau rain-
gage, a Class A land pan, and a floating pan in the pond. In order to esti-
mate evaporation from the free-water surface, corrections are necessary
for salinity. The waste flow is continually measured at the inlet to the pond
by a propeller type meter installed in the discharge pipe.
Because of the large fluctuations in chemical quality of the discharge
stream, an electrical conductivity recorder is installed on the discharge
pipe at the pond inlet. This record allows continuous monitoring of the elec-
trical conductivity of the waste discharge. Composite samples of the
waste discharge are collected for determination of trace metal content.
Weekly composites of the waste discharge samples collected at 4-hour in-
tervals are sufficient to characterize seasonal variations in chemical qual-
ity. Monthly samples of pond water are collected in order to evaluate sig-
nificant differences in chemical quality between the waste discharge and
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pond water. The primary differences are due to dilution by precipitation
and chemical reactions caused by exposure of the waste water to the atmos-
phere and sunlight in the open pond.
VADOSE ZONE MONITORING. As some trace metals in water percolat-
ing from the pond would likely be removed by sorption, chemical precipita-
tion, and other processes, the percolate and geologic materials should be
sampled. Soil-water samplers are placed in access holes drilled by power
auger beneath the pond. Three alternatives, consisting of 5, 10, and 20
holes, are considered for soil-water sampler emplacement. Three sam-
plers are emplaced in each hole at depths of 5, 10, and 15 feet beneath the
land surface depending on the actual depth to the water table. Group seals
are used to separate the samplers in each hole. During drilling, the access
holes are logged by the junior-level individual and samples of subsurface
materials are taken at 2-foot intervals. Exchangeable cations, cation ex-
change capacity, electrical conductivity, and pH of the saturation extract
are determined on selected samples. Percolate samples are taken from the
soil-water samplers on a monthly basis and electrical conductivity, pH,
arsenic, cadmium, chromium, barium, and silver contents are determined.
SATURATED ZONE MONITORING. As there are no existing wells near
the pond, a number of monitor wells are necessary. Prior to the selection
of drilling sites, a surface resistivity survey is conducted to delineate the
zone of polluted groundwater. Since much of the salinity is due to chloride,
and chloride is mobile in this soil-groundwater system, the high salinity
zone should generally delineate the maximum extent of polluted groundwater.
Other pollutants are generally less mobile and occupy smaller zones in the
groundwater. It is estimated that the zone of polluted groundwater extends
over 1/2 mile downgradient from the ponds.
From five to ten monitor wells are considered for installation by the
cable-tool method. Eight-inch diameter holes are to be drilled and 6-inch
diameter steel casing installed.
Under Alternative A, two wells would be located immediately adjacent to
the pond in the downgradient direction. One well would be drilled 500 feet
upgradient of the pond. One well would be drilled 500 feet and another 2, 000
feet downgradient of the pond. Both of the downgradient wells are within the
plume delineated by the geophysical survey. Under Alternative B, two up-
gradient wells would be drilled, at 500 feet distance, three wells near the
pond, and five wells from 500 to 2,000 feet downgradient. Wells near the
ponds are 50 feet deep and perforated from 20 to 50 feet. Upgradient and
downgradient wells are 100 feet deep and perforated from 20 to 100 feet.
After development and pump testing for 24 hours, the monitor wells are
sampled each month after 24 hours of continuous pumping. A portable sub-
mersible pump is purchased for use in all of the monitor -wells. The water
samples are analyzed for the major inorganic chemical constituents and the
five trace metals.
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Step 13 Select and Implement the Monitoring Program
Given the alternatives from Step 12, costs are derived from Everett et al.
(1976). A preliminary investigation of hydrogeology, existing water quality,
and characteristics of industrial wastes is conducted to meet the require-
ments of Steps 3 through 6. The junior-level individual spends two weeks
at $1,250 and the senior-level individual one week at $940. The preliminary
study thus costs $2, 190.
LAND SURFACE MONITORING. The costs of a recording precipitation
gage, land pan, floating pan, and flow meter are $200, $150, $200, and $100
respectively, including installation. The electrical conductivity instrument
costs $700. The annual cost for maintaining these devices is $1,000. Sam-
ple retrieval from the waste discharge by the junior-level individual re-
quires 1 day per month and costs $1, 200 per year. Analytical costs for
electrical conductivity (Everett et al. , 1976, Table 14) are $3 per sample.
Everett et al. (1976, p 114) list a group rate for analysis of drinking water
trace elements. Five of the 12 trace constituents listed are analyzed at a
group rate of $25. Analytical costs for the waste discharge are $1,460 per
year.
Collection of monthly pond samples is by small boat, requires one-half
day per month by the junior-level individual and costs $600 per year.
Analyses of the monthly pond samples for the same constituents as are in
the waste discharge costs $340 per year. Supervision by a senior-level
professional requires 1 week per year or $940. Checking chemical analy-
ses and tabulating results by a junior-level individual requires 2 weeks at
$1, 250 per year.
Total one-time costs are $1,350 for equipment. Annual costs are $1,000
for maintaining equipment, $1,800 for sample collection, $1,800 for chemi-
cal analyses, and other personnel costs are $2, 190. Total annual costs are
thus $6, 790.
VADOSE ZONE MONITORING. Costs for drilling and pressure-vacuum
soil-water sampler installation, logging, sampling of geologic materials,
chemical analyses of geologic materials, sampling of percolate, and chemi-
cal analyses of percolate for the three alternatives (A, 5 holes; B, 10 holes;
and C, 20 holes) are given in Table 5. Costs of 8-inch diameter augered
holes are determined from Everett et al. (1976, Figure 6). Five holes are
$50 per hole, 10 holes are $45 per hole, and 20 holes are $40 per hole. Due
to the low density of holes in this example these values are extrapolated
from the data on Figure 6 of Everett et al. (1976). Soil-water samplers
cost $70 for each hole and one service kit costs $30. Geologic logging and
sampling require 1 day for five holes, 2 days for 10 holes, and 4 days for
20 holes, all by the junior-level individual. Chemical analyses of subsur-
face materials are performed on samples at 5-foot depth intervals, including
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TABLE 5. COSTS FOR MONITORING THE VADOSE ZONE
Alternatives
(cost in dollars)
COST COMPONENTS
One-time Costs
Drilling and Sampler Installation
(including sampler)
Geologic Logging and Sampling
Materials
Chemical Analyses of Materials
TOTAL
Annual Costs
Sampling of Percolate
Chemical Analyses of Percolate
TOTAL
A
630
130
500
1,260
130
5,400
5,530
B
1,180
250
880
2,310
250
9,720
9,970
C
2,230
380
1,600
4,210
380
17,280
17,660
one at the land surface. Cation exchange capacity is $11 per sample from
Everett et al. (1976, p 112). Electrical conductivity of the saturation ex-
tract is $5. 50 per sample from Everett et al. (1976, p 112). The pH of the
saturation extract is $2.50 per sample from Everett et al. (1976, p 112).
The exchangeable cations are $12 per sample from Everett et al. (1976,
p 113). In this case a special group rate of $25 per sample is used. The
determinations are discounted to $22 per sample for 25 samples, $20 per
sample for 50 samples, and $18 per sample for 100 samples.
Sampling of percolate requires 1 day per month for 5 holes, 2 days for
10 holes, and 3 days for 20 holes, all by the junior-level individual. Costs
for analytical determinations of the five trace metals in the percolate are
$25 per sample. The trace metals were selected from the 12 listed by
Everett et al. (1976, p 114) and a special group rate was applied. Electri-
cal conductivity and pH (Everett et al. , 1976, Table 14) are $3 each. A
special group rate for all of these determinations of $30 is applied. Chem-
ical analyses for monthly percolate samples are $30 per sample up to 30
samples, $27 per sample for 30 samples, and $24 per sample for 60 sam-
ples.
SATURATED ZONE MONITORING. The cost of the surface resistivity
survey is determined from Everett et al. (1976, Table 6). The depth to
top of the plume is 20 feet and the plume is estimated to be 50 feet thick.
The areal extent of the plume is estimated at 50 acres. Based on an elec-
trode spread of 100 feet, six surveys totaling about 18 hours would be re-
quired. At $80 per hour, the total cost is about $1,400.
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For Alternative A, two monitor wells are drilled near the pond to a
depth of 50 feet and the remaining three wells are 100 feet deep. For Al-
ternative B, three monitor wells are 50 feet deep and the remaining seven
are 100 feet. Monitor-well drilling costs are calculated from Everett et al.
(1976, Figure 19). A 6-inch casing is necessary to permit installation of
a 50-gpm capacity pump at the estimated lift of 60 feet (Everett et al. , 1976,
Table 11). Well drilling costs, including casing and well development, are
about $2,600 each for the 100-foot deep monitor wells and $1,700 each for
the 50-foot deep monitor wells. Logging requires 1 day of the junior-level
individual's time for five wells and 2 days for ten wells. The logging cost
is $125 for five wells and $250 for ten wells.
Twenty- four -hour pump tests are run on each monitor well at a cost of
$20 per hour exclusive of the junior-level individual's time. His time for
pump tests, tabulating and plotting results, and interpretation is 4 days per
well. Costs for pump tests including the junior-level individual's time are
$980 per well. Chemical analyses are made for pumped water during the
pump test. The major inorganic chemical constituents are determined at
$12 per sample (Everett et al. , 1976, p 114) and five trace metals are run
at $25 per sample (Everett et al. , 1976, p 114). A group rate is applied for
five of the 12 drinking water trace element determinations. Chemical
analyses are thus $37 per sample, or $185 for Alternative A and $370 for
Alternative B.
A portable 2-hp submersible pump costs $500 (Everett et al. , 1976,
Table 11). Eighty feet of cable are an additional $70 (Everett et al. , 1976,
Figure 26). Sample retrieval requires 5 days of pumping per month for
five monitor wells, and 10 days for ten monitor wells at $50 per day. An-
nual pumping costs are thus $3, 000 for Alternative A and $6, 000 for Al-
ternative B. The monthly samples of water from the monitor wells are
analyzed for the major inorganic chemical constituents and the five trace
elements. Chemical analyses for the monitor well water are $37 per sam-
ple, as determined previously.
Time required of the junior-level individual for sampling, checking
chemical analyses, and tabulating results is 1 month for Alternative A and
4 months for Alternative B. Supervision by the senior-level individual is
1 week for Alternative A and 2 weeks for Alternative B. Table 6 summa-
rizes costs for monitoring the saturated zone.
In order to select the most cost-effective alternatives, consideration is
given to impacts of groundwater pollution on subsequent groundwater use.
In this case, no groundwater is presently used, but it is projected that
groundwater will be used for municipal purposes in 20 years. Arsenic,
cadmium, and hexavalent chromium pose a distinct health threat to ground-
water used for drinking purposes. The high salinity, chloride, and sodium
contents could easily render groundwater near the disposal site unusable.
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TABLE 6. COSTS FOR SATURATED ZONE MONITORING
Alternatives
(cost in dollars)
COST COMPONENTS
One-time Costs
Surface Resistivity Survey
Drilling, Casing, and Development
for Monitor Wells
Logging, Pump Testing, and
Chemical Analyses
Portable Submersible Pump
TOTAL
Annual Costs
Pumping for Monthly Sample
Retrieval
Chemical Analyses of Monthly
Samples
Personnel
TOTAL
A
1,400
11,200
5,210
570
18,380
3,000
2,220
3,440
8,660
B
1,400
23,300
10,420
570
35,690
6,000
4,440
6,880
17,320
Secondly, the net worth of the industrial product has to be considered. A
final consideration is the money available for monitoring the site. Con-
sideration of all these factors, in conjunction with experience in monitoring
groundwater pollution, leads to selection of Alternative B for the vadose
zone and Alternative A for the saturated zone.
SUMMARY. Total costs for the program selected are given in Table 7.
TABLE 7. TOTAL COSTS FOR MONITORING INDUSTRIAL WASTE
PERCOLATION POND
Monitoring Costs (dollars)
Cost Components
Preliminary Investigation
Surface Monitoring
Vadose Zone Monitoring
Saturated Zone Monitoring
TOTAL
One -Time
2,190
1,350
2,310
18,380
24,230
Annual
6,790
9,970
8,660
25,420
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SOLID WASTE LANDFILLS
The area selected to monitor above the water table includes the landfill
itself. In many areas tens of feet of soil and geologic materials have been
excavated and replaced by solid wastes comprising the landfill. Sampling
and analysis are done to determine the composition of the solid materials
emplaced in the landfill, the leachate, and percolate in the vadose zone. If
impermeable layers underlie the landfill, vadose zone monitoring may be
necessary for distances of several hundred feet laterally from the landfill.
Sampling of leachate and shallow groundwater is almost always necessary.
Groundwater should generally be monitored for a distance of at least several
hundred or several thousand feet from the landfill. Sampling of topsoil and
geologic materials for toxic constituents may be necessary.
Land Surface Monitoring
Land surface monitoring encompasses an inventory of the volumes or
weights of solid materials emplaced in the landfill. Rainfall and evapotrans-
piration rates must be known and can often be extrapolated from nearby
meteorological stations. Compilation of these data allows calculation of the
potential leachate production. The moisture characteristics of the solid
wa'stes should be monitored, and usually shallow holes drilled by augering
will suffice. It is important to determine if aerobic or anaerobic decompo-
sition is occurring at specific locations. This depends on the moisture con-
tent of the landfill, depth to groundwater, groundwater inflow, and other
factors. Detection of leakage is a prime concern for landfills with liners
installed to limit percolation.
The chemical composition of solid materials in the landfill and in the
leachate must be determined. The composition of landfill materials can
often be broadly characterized, whereas detailed sampling of leachate is
often necessary to determine its composition. The frequency of leachate
sample collection depends highly on the frequency and rate of rainfall.
Rather than a uniform sampling frequency, samples should be collected at
intervals based on the rate of leachate production. The approximate
volumes and quality of other sources of recharge and groundwater inflow
must also be determined.
Leachate analyses should include the major inorganic chemical species,
nitrogen forms, total dissolved solids, pH, and oxidation potential. The
primary metals in the landfill that may be leached should be determined.
Examples are iron, manganese, barium, chromium, lead, selenium, and
zinc.
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Vadose Zone Monitoring
Monitoring in the vadose zone includes determination of percolate qual-
ity, flow rate, attenuation characteristics of soil and geologic materials,
and chemical analyses of solid materials. In areas of low rainfall, little
or no leachate will be produced and sampling in the vadose zone may be un-
necessary. Test drilling is often necessary in or near landfills because of
a lack of information on materials comprising the vadose zone. Drilling of
test holes can provide geologic information on the vadose zone and permit
the installation of devices for water sample retrieval. Neutron probes can
be effectively used to trace water movement above the water table when
necessary. Analytical determinations for percolate quality include the ma-
jor inorganic chemical constituents, nitrogen forms, selected trace metals,
particularly iron and manganese, and oxidation potential. Cation exchange
capacity, electrical conductivity, pH, and exchangeable cations are impor-
tant analyses for soil and geologic materials.
Saturated Zone Monitoring
Wells have often been successfully used in monitoring groundwater pol-
lution beneath or near solid waste disposal sites. In areas of moderate to
heavy rainfall, significant amounts of leachate are produced. Most or all
of the leachate can subsequently percolate to the groundwater. Monitor
wells may be installed and sampled. Monthly sampling appears to be suf-
ficient in most cases. Several existing large-capacity wells in the area
should also be periodically sampled. A portable submersible pump can be
used to pump water for sampling from a number of test wells in one area,
thus avoiding the cost of equipping each well with a permanent pump. Anal-
yses of water from wells are similar to those for percolate quality, but can
be modified to reflect the water usage in the area. As leachate is generally
high in total dissolved solids, surface resistivity surveys can be used in
some cases to delineate the extent of polluted groundwater. In general the
water table must be shallow and groundwater conditions fairly well under-
stood. Remote sensing can provide information in areas where the water
table is shallow, and/or the leachate is forced to the land surface.
SOLID WASTE LANDFILL EXAMPLE
Step 2 Identify Pollution Sources, Causes/
and Methods of Waste Disposal
In this example a 20-acre landfill in the southeastern United States is to
be monitored. The landfill has been in operation for 10 years. The land-
fill receives solid refuse from a medium-sized city and a plastic liner has
been installed to limit percolation. The other potential sources of ground-
water pollution include small amounts of fertilizers, scattered septic tanks
and polluted rainfall. Evaluation of these other sources indicates that they
are generally insignificant.
71
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Step 3 Identify Potential Pollutants
The liner has been graded toward a central point so that leachate sam-
ples can be collected. Previous analyses of grab samples obtained from a
sump drain have indicated that the quality of the leachate is similar to that
to be expected from such a source. The leachate contains high total dis-
solved solids concentrations, some organic chemicals, and selected trace
elements. Materials placed in the landfill indicate that chloride, nitrogen
forms, potassium, calcium, sulfate, iron, manganese, lead, silver, chro-
mium, cadmium, and zinc are of concern.
Step 4 Define Groundwater Usage
Wells in this rural area are used primarily for domestic purposes, how-
ever, small amounts of groundwater are used for crop irrigation. Of all
groundwater pumpage, about 80 percent is for domestic use and the remain-
der for irrigation.
Step 5 Define Hydrogeologic Situation
The average annual rainfall in the area is 40 inches. Alluvial deposits
about 50 feet thick overlie hundreds of feet of permeable limestone. Both
the alluvium and limestone are developed aquifers in the region and beneath
the landfill the hydraulic head is lower in the limestone than in the alluvium.
A number of water level measurements in wells in the two aquifers are
available and indicate the regional direction of groundwater movement. The
water table in the alluvium is about 20 feet beneath the landfill and water in
the limestone is under artesian pressure. Groundwater in the alluvium
tends to move toward a stream about 1 mile downgradient. There is a ten-
dency for downward movement of shallow groundwater into the confined
groundwater in the limestone. The extent of the polluted zone in the allu-
vium has been previously delineated, but the extent of pollution in the lower
aquifer is unknown. There are several wells within the polluted zone in the
alluvium.
Annual recharge to both aquifers was previously calculated by the U. S.
Geological Survey. Annual pumpage from both aquifers in the region is
about 20, 000 acre-feet, whereas annual recharge to both aquifers is about
100, 000 acre-feet.
Step 6 Study Existing Groundwater Quality
Previous studies by the U. S. Geological Survey have delineated the re-
gional groundwater quality. Groundwater in the limestone is calcium bi-
carbonate in type with total dissolved solids less than 100 ppm. Ground-
water in the alluvium has a greater variation in chemical quality than
groundwater in the limestone. Alluvial groundwater is generally a sodium-
72
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calcium bicarbonate type and total dissolved solids range from about 70 to
500 ppm. Beneath the landfill, groundwater is a sodium bicarbonate-
chloride type, with high nitrate, chromium, iron, and manganese contents.
Maps are available indicating the regional distribution of total dissolved
solids, chloride, and nitrate in both aquifers.
Step 7 Evaluate Infiltration Potential of
Wastes at the Land Surface
Water budget analysis is unnecessary due to the presence of the liner
which greatly limits percolation of leachate. The presence of a polluted
zone of groundwater beneath the site is ample indication that limited seepage
and/or leakage has occurred. There was no inspection of the liner during
installation and there has been no monitoring of the liner integrity.
Step 8 Evaluate Mobility of Pollutants
from the Land Surface to the Water Table
Neutron probe moisture logging and soil-water sampling were done in a
similar hydrogeologic situation by researchers at a nearby university.
This research indicated travel times of leachate to the shallow water table
of several weeks to months. Attenuation of bacteriological constituents and
some organic chemicals and trace elements was noted. These results
could be directly extrapolated to the study area.
Step 9 Evaluate Attenuation of Pollutants
in the Saturated Zone
A surface resistivity survey was previously conducted to delineate the
extent of the polluted zone in the alluvium. Several existing wells tap the
alluvium, both in and outside of the polluted zone. However, although sev-
eral nearby wells tap the limestone, no such wells are in the anticipated
polluted zone. The extent of the polluted zone determined by resistivity
measurements corresponds to high total dissolved solids content. Previous
well sampling indicates that high calcium, bicarbonate, and chloride con-
tents also occur in this zone. Several trace metals occur in high concen-
tration, however, over a smaller zone. This is believed to be due primar-
ily to precipitation and adsorption.
Step 11 Evaluate Existing Monitoring Programs
Existing programs in the area of most direct value are related to moni-
toring in the vadose zone. There is no routine program for leachate sam-
pling at the landfill, nor is there any for routine well sampling in the im-
mediate vicinity of the landfill.
73
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Step 12 Establish Alternative Monitoring Approaches
Consideration of information developed in the previous steps indicate that
no additional monitoring in the vadose zone is necessary. Routine sampling
of leachate, well drilling, and water sampling from wells are deemed neces-
sary. Hydrogeologic judgment is used to select the most effective moni-
toring program in each case.
To determine cost-effectiveness, consideration is given to water use in
areas that could be impacted by the waste disposal. Most of the water use
is for domestic purposes, and due to the rural nature of the area, ground-
water is considered the sole source of the drinking water supply. Nitrate,
chromium, and cadmium pose a potential threat to health for persons drink-
ing water from wells in the polluted zone. The maximum extent of the pol-
luted zone is believed to not exceed 1, 000 acres for the alluvium. For the
limestone the maximum extent is believed to not exceed 200 acres. Within
these areas at present, only three wells are used for drinking water pur-
poses, serving a total of ten people. Given the rural nature of the area and
projected land use, this situation should not greatly change in the next 30
years.
Inorganic chemical constituents may also pose a health threat. Chloride,
sulfate, calcium, iron, and manganese may degrade drinking water. In-
creased total dissolved solids from pollution may decrease crop yields in a
small area near the pond.
LAND SURFACE MONITORING. As part of the recommended monitor-
ing program, leachate samples will be collected daily for electrical con-
ductivity determinations. In turn, these samples will be composited weekly
for analysis. The major inorganic chemical constituents, total nitrogen,
COD, dissolved oxygen, iron, manganese, lead, silver, chromium, cad-
mium, and zinc will be determined.
SATURATED ZONE MONITORING. Monitoring includes routine sam-
pling of water from existing wells and drilling of additional wells in the
limestone for water sampling. Three monitor wells are to be drilled into
the limestone by the cable-tool method. These wells are 300 feet deep and
perforated from 100 to 300 feet. The water level in the wells is only 60
feet below the landfill due to the artesian condition existing in the limestone
aquifer. Hole diameter is 8 inches and casing diameter is 6 inches. After
development, 1-week pump tests are conducted and permanent submersible
pumps of 25 gpm capacity at 75-foot lift are installed. The pump tests
provide information on the hydraulic connection of the upper and lower
aquifer, as well as vertical permeability of the confining bed for the con-
fined aquifer. The electrical conductivity and temperature of the water
discharged are frequently measured. On this basis, five water samples
are chosen for routine chemical analyses for each well, including the seven
trace metals listed previously.
74
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For the first year, monthly samples are collected from these three wells
and five previously existing wells. The major inorganic chemicals are de-
termined, including iron, manganese, chromium, and cadmium. Lead,
silver, and zinc are deleted from the program because of attenuation char-
acteristics of materials above the water table. After the first year, quar-
terly samples from five wells are sufficient.
Step 13 Select and Implement the Monitoring Program
As the approach has already been determined in Step 12, this step pri-
marily involves determination of costs. A preliminary investigation is
conducted to meet the requirements of Steps 3 through 6 including collection
and interpretation of records on groundwater conditions, water quality,
landfills, and leachate. The junior-level individual spends 1 month at a
cost of $2, 500. The senior-level individual spends 1 week at a cost of
$940. The cost of this phase is thus $3,440.
LAND SURFACE MONITORING. A portable meter for daily electrical
conductivity determinations costs $350. Leachate samples are taken by the
caretaker at no additional expense. Major inorganic chemical constituents
determinations are $12 per sample (Everett et al. , 1976, p 114). The
seven trace elements determinations are $30 per sample based on a group
rate derived from the 12 drinking water trace elements from Everett et al.
(1976, p 114). Dissolved oxygen determinations are $5 per sample from
Everett et al. (1976, Table 14). Chemical oxygen demand determinations
are $10 per sample from Everett et al. (1976, Table 15). Total nitrogen
determinations are $10 per sample from Everett et al. (1976, Table 14).
Leachate analyses on a weekly basis are $67, or $3,480 during the first
year. Checking chemical analyses and plotting results during the first year
requires 1 month of time by the junior professional at a cost of $2, 500.
Supervision by a senior level professional during the first year totals 1 week
at a cost of $940. After the first year, weekly samples are composited and
analyzed monthly. Thus, analytical costs after the first year are $804 per
year. Personnel time after the first year includes 2 weeks for the junior-
level individual at $1,250 and one-half week by the senior-level individual
at $470.
VADOSE ZONE MONITORING. Review of existing studies requires 2
weeks by a junior professional at $1,250 and 1 week by a senior professional
at $940. Total one-time costs are $2, 190.
SATURATED ZONE MONITORING. Drilling costs are about $3,800
each for 8-inch diameter holes with 6-inch steel casing (Everett et al. ,
1976, Figure 20 - for consolidated formations). The pump tests of 1 week
duration for each well are conducted at a cost of $3, 500 per well, exclusive
of geologist time. The junior professional spends 1 day logging cuttings
75
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and 2 weeks for pump tests (including interpretation) on each well. Person-
nel costs for well-logging, pump testing, and aquifer analysis are $1,460
per well.
Major inorganic chemical constituents are determined at $12 per sample
from Everett et al. (1976, p 114). Seven trace elements are determined at
$30 per sample from Everett et al. (1976, p 114), applying a special group
rate. Chemical analyses are $42 each for the five water samples collected
during the pump test for each well. Three 1-hp submersible pumps with
25-gpm capacity at the projected 75-foot lift cost $300 each. Three hundred
feet of cable for the pumps costs $240 (Everett et al. , 1976, Figure 26).
Supervision by the senior-level individual for this phase is 3 weeks at a cost
of $2, 830. Total one-time cost for this phase of the program is $29, 070.
Water samples are collected at no pumping cost, as the monitor wells
are also used for water supply in the area. Sampling can be done during
normal operation of the pump by the user. Major inorganic chemical con-
stituents are determined for $12 per sample (Everett et al. , 1976, p 114).
The four trace metals are analyzed at a cost of $17 per sample, applying
a discount rate to that given for the 12 drinking water trace constituents
from Everett et al. (1976, p 114). Costs for the water analyses are $29
per sample. Monthly analyses during the first year total $2, 784. Sample
collection, checking chemical analyses, and tabulating results require 1
month of the junior-level individual's time, at a cost of $2,500. Supervision
by the senior-level individual requires 1 week at $940.
After the first year, analytical costs are $145 per quarterly sampling
round, or $580 per year. The junior-level individual spends 2 weeks an-
nually after the first year at a cost of $1, 250. The senior professional
spends one-half week at a cost of $470.
SUMMARY. Total monitoring costs are summarized in Table 8.
TABLE 8. MONITORING COSTS FOR SOLID WASTE LANDFILL
Cost Component
Preliminary Investigation
Land Surface Monitoring
Monitoring Vadose Zone
Monitoring Saturated Zone
TOTAL
One-Time
3,440
350
2,190
30,870
367850
Cost (dollars)
Annual
First
Year
6,920
6,224
13, 144
Annual
Subsequent
Years
1,720
2,300
4,020
76
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REFERENCES
American Water Works Association, "Sources of Nitrogen and Phosphorus
in Water Supplies, " Journal of American Water Works Association,
Task Group Report, pp 344-366, March 1967.
Behnke, J. J. , and E. E. Haskell, "Ground Water Nitrate Distribution Be-
neath Fresno, California, " Journal of American Water Works Asso-
ciation. Vol 60, No, 4, pp 477-480, 1968.
Bouwer, H. , "Renovating Secondary Effluent by Groundwater Recharge with
Infiltration Basins, " Recycling Treated Municipal Wastewatcr and
Sludge through Forest and Cropland, W. E. Sopper and L. T. Kardos
(eds), Pennsylvania State University Press, 1973.
California Department of Water Resources, Fresno-Clovis Metropolitan
Area Water Quality Investigation, Bulletin 143-3, 1965.
Davidson, E. S. , Geohydrology and Water Resources of the Tucson Basin,
A rizona, U.S. Geological Survey, Water Supply Paper 1939-E, 1Q73.
Ellis, B. G. , "The Soil as a Chemical Filter, " Recycling Treated Municipal
Wastewater and Sludge through Forest and Cropland^ W. E. Sopper
and L. T. Kardos (eds). Pennsylvania State University Press, 1973.
Everett, L. G. , K, D. Schmidt, R. M. Tinlin, and D. K. To-id, Monitoring
Groundwater Quality: Methods and Costs, EPA-600/4-76 -023, U.S.
Environmental Protection Agency, Las Vegas, Nevada, May 1976.
Fryberger, J. S. , Rehabilitation of a Brine-Polluted Aquifer, EPA-R2-72-
014, Environmental Protection Technology Series, 1Q72.
Geraghty and Miller, Inc. , Geologic and Hydrologic Investigation of the
Proposed Silver Sands State ParkJ Milford, Connecticut, for the Con-
necticut Departments of Public Works and Environmental Protection,
1973.
Lehman, G. S. , Soil and Grass Filtration of Domestic Sewage Effluent for
the Removal of Trace Elements, unpublished Ph.D. Dissertation,
University of Arizona, 1968.
77
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Ludwig, A. H. , Water Resources of Hempstead, Lafayette, Little Rock.
Miller and Nevada Counties, Arkansas^ Geological Survey Water Sup-
ply Paper 1998, 1973.
Matlock, W. G. , P. R. Davis, and R. L. Roth, Sewage Pollution of a Ground-
water Aquifer, Paper presented at the 1972 Winter Meeting of Ameri-
can Society of Agricultural Engineers, Chicago, Illinois, 1972.
Miller, R. H. , "The Soil as a Biological Filter, " Recycling Treated Muni-
cipal_ Waste-water and Sludge through Forest and Cropland, W. E. Sop-
per and L. T. Kardos (eds), Pennsylvania State University Press, 1973.
Nightingale, H. I. , "Nitrates in Soil and Ground Water Beneath Irrigated and
Fertilized Crops, " Soil Science. Vol 114, No. 4, pp 300-311, 1972.
Nightingale, H. I. , "Statistical Evaluation of Salinity and Nitrate Content and
Trends Beneath Urban and Agricultural Areas Fresno, California, "
Ground Water, Vol 8, No. 1, pp 22-28, 1970.
Oklahoma Water Resources Board, Salt Water Detection in the Cimarron
Terrace, Oklahoma, EPA-660/3-74-033, 1974.
Page, R. W. , and R. A. LeBlanc, Geology. Hydrology, and Water Quality
in the Fresno Area, California, U.S. Geological Survey Open-File
Report, Menlo Park, California, 189 pp, 1969.
Perlmutter, N. M. , and J. J. Geraghty, Geology and Ground-water Conditions
in Southern Nassau and Southeastern Queens Counties, Long Island,
New York, U.S. Geological Survey Water-Supply Paper 1613-A, 205 pp,
1963.
Perlmutter, N. M. , and M. Lieber, Disposal of Plating Wastes and Sewage
Contaminants in Ground Water and Surface Water, South Farmingdale
Massapequa Area, Nassau County, New York, U. S. Geological
Survey Water-Supply Paper 1879G, 1970.
Perlmutter, N. M. , M. Lieber and H. L. Frauenthal, "Movement of Water-
borne Cadmium and Hexavalent Chromium Wastes in South Farming-
dale, Nassau County, Long Island, New York, " Short papers in Geol-
ogy and Hydrology U.S. Geological Survey Professional Paper 475-C,
pp C179-C184, 1963.
Pinder, G. F. , "A Galerkin-Finite Element Simulation of Ground-Water Con-
tamination on Long Island, N. Y. , " Water Resources Research, Vol 9,
No. 6, pp 1657-1669, 1973.
78
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Randall, J. H. , Hydro geology and Water Quality. .Pirn a County Landfill
Project, Unpublished Report, University of Arizona, 1974.
Schmidt, K. D. , "Regional Sewering and Groundwater Quality in the Southern
San Joaquin Valley, " Water Resources Bulletin, Vol 11, No. 3, pp
514-525, 1975.
Schmidt, K. D. , "Groundwater Contamination in the Cortaro Area, Pima
County, Arizona, " Hydrology and Water Resources in Arizona and
the Southwest, Vol 2, Proceedings of 1972 Meetings of Arizona Sec-
tion, American Water Resources Association, Prescott, Arizona,
May 5-6, 1972a.
Schmidt, K. D. , "Nitrate in Ground Water of the Fresno-Clovis Metropoli-
tan Area, " GrjJundJVaJter, Vol 10, No. 1, pp 50-64, 1972b.
Schroepfer, G. J. , and R. C. Polta, Travel of Nitrogen Compounds in Soils,
University of Minnesota, Sanitary Engineering Report 172-5, 1969.
Small, G. G. , Groundwater Recharge and Quality Transformations During
the Initiation and Management of a New Stabilization Lagoon, Unpub-
lished M.S. Thesis, University of Arizona, 1973.
Stout, P. R. , R. G. Burau and W. R. Allardice, A Study of The Vertical
Movement of Nitrogenous Matter from the Ground Surface to the
Water Table in the Vicinity of Grover City and Arroyo Grande, San
Lui s Obi spo County, Report to Central Coastal Regional Water Pol-
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Suter, R. , W. deLaguna, and N. M. Perlmutter, Mapping of Geologic For-
mations and Aquifers of Long Island, New York, New York Water
Power and Control Commission Bulletin GW-18, 212 pp, 1949.
Todd, D. K. , R. M. Tinlin, K. D. Schmidt, and L. G. Everett, Monitoring
Groundwater Quality; Monitoring Methodology, (in press) U. S. En-
vironmental Protection Agency, Las Vegas, Nevada, 1976.
Walton, W. C. , Groundwater Resource Evaluation, McGraw-Hill Book Co. ,
1970.
Wilson, L. G. , Quality Transformation in Recharged River Water During
Possible Interactions with Landfill Deposits Along the Santa Cruz
River, Annual Report to Pima County Department of Sanitation, Water
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Wilson, L. G. , "Observations on Water Content Changes in Stratified Sedi-
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1971.
Wilson, L. G. , W. L. Clark III and G. G. Small, "Subsurface Transforma-
tions During the Initiation of a New Stabilization Lagoon, Water Re-
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Wilson, L. G. , and K. J. DeCook, "Field Observations on Changes in the
Subsurface Water Regime During Influent Seepage in the Santa Cruz
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80
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APPENDIX
METRIC CONVERSION TABLE*
Non-Metric Unit
inch (in)
feet (ft)
miles
acres
gallons (gal)
pounds per square inch (psi)
parts per million (ppm)
gallons per minute (gpm)
Multiply by
25.4
0.3048
1.60934
0.404686
3.7854
0.0680460
1
3.7854
Metric Unit
millimeters (mm)
meters (m)
kilometers (km)
hectares (ha)
liters (1)
atmospheres (atm)
milligrams per liter
(mg/1)
liters (1) per minute
*English units were used in this report because the data obtained were not
available in metric units.
81
691-926-1976
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA 600/4-76-036
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
MONITORING GROUNDWATER QUALITY:
5. REPORT DATE
ILLUSTRATIVE EXAMPLES
July 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Richard M. Tinlin, Editor
8. PERFORMING ORGANIZATION REPORT NO.
GE75TMP-72
9. PERFORMING ORGANIZATION NAME AND ADDRESS
General Electric Company-TEMPO
Center for Advanced Studies
P. 0. Drawer QQ
Santa Barbara, California 93102
10. PROGRAM ELEMENT NO.
1HD620
11. CONTRACT/GRANT NO.
69-01-0759
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, Nevada 89114
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA-ORD Office of Monitoring
and Technical Support
15. SUPPLEMENTARY NOTES
This is one of 5 final reports in a series of 11 documents prepared on
monitoring groundwater quality.
16. ABSTRACT
This report is designed to show by example site-specific procedures for monitoring
various classes of groundwater pollution sources. The first of five case histories
of actual or potential groundwater pollution are presented with the monitoring
techniques and their efficacy. The case histories cover brine disposal in Arkansas,
plating waste contamination in Long Island, New York, landfill leachate pollution
in Milford, Conneticut, an oxidation pond near Tucson, Arizona, and multiple-source
nitrate pollution in the Fresno-Clovis, California, metropolitan area. The report
concludes with hypothetical illustrative examples for developing and selecting
monitoring alternatives based on a cost comparison between other alternatives and
hydrologic judgment. The examples illustrated cover agricultural return flow,
septic tanks, percolation ponds, and landfills.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Groundwater
Monitoring
Water quality
Water pollution
Water resources
Water wells
Aquifers
Plating waste contamina-
tion
Landfill leachate
Oxidation ponds
Brine disposal
Nitrate pollution
Septic tanks
08H
13B
8. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21 NO. OF PAGES
92
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 22ZO-1 (9-73)
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