5542
905R80129
THE NATIONAL ASSESSMENT OF THE GROUND-WATER CONTAMINATION
' POTENTIAL OF WASTE IMPOUNDMENTS
By
Lyle R. Silka and Francoise M. Brasier
Presented at
The Symposiun on Surface-Water Impoundments
Minneapolis, MN
June 2-5, 1980
U.S. Environmental Protection Agency
Washington, D.C. 20460
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U,S. Environmental Protection Agency
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THE NATIONAL ASSESSMENT OF THE GROUND-WATER CONTAMINATION
POTENTIAL OF WASTE IMPOUNDMENTS
by
1)
Lyle R. Silka and Francoise M. Brasier
BACKGROUND
Preliminary studies by the Environmental Protection Agency (2,3)
indicated that the storage, treatment and disposal of liquid wastes in
surface impoundments (pits, ponds and lagoons) may be a significant
source of ground-water contamination; yet large gaps exist in the
knowledge of the numbers, location or construction of surface
impoundments at either the State or Federal levels. Pursuant to
§1442 (b) (3)(C) of the Safe Drinking Water Act, the EPA made available
$5 million to the States in 1978 to conduct a study of the magnitude
and potential effects of waste disposal on ground water. Specific
objectives of the "Surface Impoundment Assessment" (SIA) were to: 1)
increase the States' awareness and data base concerning impoundments;
2) determine their numbers, location and potential effects on ground
water; 3) solicit States' positions and suggestions on the Federal
role in ground-water protection from this contamination source; and
provide EPA with information to allow an analysis of EPA' s mandates
and programs regarding ground-water protection and surface
impoundments.
1)
Hydrogeologist and Consulting Geologist, U.S. Environmental
Protection Agency, Washington, DC 20460
2)
EPA, 1978, Surface Impoundments and Their Effects on Ground-Water
Quality in the United StatesA Preliminary Survey,
EPA 570/9-78-004.
3)
EPA, 1977, The Prevalence of Subsurface Migration of Hazardous
Chemical Substances at Selected Industrial Waste Land Disposal
Sites, EPA 530/SW-634.
--''..;::-.--'-; Protection Agenjy
".'.:-C~l V, Jj:..;'/
/',0 COL;:'-! rv.- ' .. - ' . -~ 1 " Silka, Brasier
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METHODODDGY
The SIA was initiated in 1978 with a series of nine training sessions
around the country to train the 250 professionals responsible for the
conduct of the SIA in the States. An evaluation methodology was
developed for the SIA to assist in the assessment of the potential
effects of surface impoundments on ground-water quality (4). This
evaluation scheme assigns ratings to a site based on the following
steps:
1. the permeability and thickness of the earth material
above the water table (a measure of the relative rate at
which liquid waste could infiltrate through the unsaturated
zone to reach the ground water);
2. the quantity of ground water present (the permeability
and thickness of the aquifer);
3. the quality of the ground water (combining Step 2 and
Step 3 provides a rating of the usability of the
aquifer);
4. the potential hazard or toxicity of the liquid waste
(based on general industry waste characteristics);
5. the overall potential for ground-water contamination (the
sum of the first four steps); and
6. the potential for a nearby water supply well or surface
water body to became contaminated (this involves the
estimation of the flow path of contaminated ground water
and whether it would intersect a well or surface water) .
In addition, information on impoundment liners and ground-water
quality monitoring was collected.
4)
EPA, 1978, A Manual for Evaluating Contamination Potential of
Surface Impoundments, by Lyle R. Silka and Ted L. Swearingen, EPA
570/9-78-003.
2 " Silka, Brasier
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The SIA evaluation system is intended as a first-round approximation
which provides an indication of the relative potential for
ground-water contamination. The results of the assessments in the SIA
are not suitable for enforcement purposes, but are important for
prioritization of sites from high to low ground-water contamination
potential. Such a prioritization scheme allows the in-depth
investigations required for enforcement activities to be conducted in
an efficient and cost effective manner, optimally utilizing the
limited resources available to identify those sites for which
investigations should proceed first. This strategy is being
implemented in the U.S. Environmental Protection Agency's programs
under the Resource Conservation and Recovery Act and the Hazardous
Waste Enforcement Task Force actively dealing with uncontrolled
hazardous waste.
The limited funds available to the SIA restricted the scope of the
study. Greatest emphasis was placed on the location of surface
impoundments and then on their assessment. At a minimum, the State
was to exhaust all reasonable possibilities to locate impoundments.
Of the funds remaining after locating impoundments, the State was
required to spend at least 50% to 80% on assessing industrial sites.
This assessment was to be performed on a statistically random
selection of sites if insufficient funds remained to assess all the
located sites. Thirty-one States conducted assessments on over 90% of
their located industrial sites, while an additional twelve States
assessed over 50%. Nationally, almost 80% of the industrial sites
located in the SIA were assessed as to their ground-water
contamination potential as of February 15, 1980.
Table I on page 4 provides a summary of the nunbers of sites and
impoundments located in each of the five major categories by the SIA
to date.
FINDINGS
The data presented in this report represent averages of broad
categories. Accordingly, specific subcategories within the major
categories may have quite different characteristics than those
presented here. For example, impoundment surface areas in non-coal
mining (presented in Table II) can vary between less than one acre for
some operations (e.g., precious metal mining) to over 100 acres for
others (e.g., phosphate mining). The analyses have been presented in
these categories to render the data manageable for this paper. More
specific analyses of the data will be presented in the final National
Surface Impoundment Assessment report to be published in late 1980.
Silka, Brasier
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TABLE I
Sunmary Statistics
for Located Waste Impoundment Sites
Category
Industrial
Municipal
Agricultural
Mining
Non-Goal
Goal
Oil & Gas
Brine Pits
Other
TOTAL
Located
Sites
10,819
19,102
14,373
1,688
5,388*
24,527*
1,781
77,678
Assessed
Sites
8,163
10,792
6,562
616
837
3,314
680
30,964
Located
Impoundments
25,749
36,161
18,765
4,026
20,350
64,951
6,645
176,647
* SIA site numbers for the mining and oil & gas brine pit
sites are not necessarily related to actual ownership and
should not be referred to as the actual nunber of legal
sites. The number of located impoundments would be a
closer approximation for these two categories.
Silka, Brasier
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A preliminary analysis of the SIA data indicates the following for the
8163 assessed industrial sites.
Surface Area. An extrapolation of the surface area of impoundments
for which data is available to the approximately 26,000 industrial
impoundments indicates about 430,000 acres of impoundments are
currently in use (Table II).
Influent Volume into Waste Impoundments. Available data collected by
the study indicates that the influent volune of waste water into
industrial impoundments is on the order of 50 billion gallons per day
(Table II).
Liners. Over 70% of the industrial impoundments are unlined,
potentially allowing contaminants to infiltrate unimpeded into the
subsurface (Table II).
Ground-Water Monitoring. Less than 10% of the sites have any
ground-water monitoring and only about one-half of these are regularly
sampled. Thus, nearly 95% of the sites are virtually unmonitored as
to possible ground-water contamination (Table III).
Waste Character. Approximately 50% of the impoundments contain liquid
waste which may have potentially hazardous constituents, based on the
Standard Industrial Classification code (Table III). The other 50%
may not contain potentially hazardous constituents, but they still may
contain contaminants which, while not endangering health, may cause
degradation of the ground-water quality forcing use of that resource
to be discontinued or increased treatment of the water prior to use.
Siting. Thirty percent of the industrial impoundments, are unlined,
overlie usable aquifers and are underlain by unsaturated zones which
freely allow downward movement of any liquid wastes escaping from the
impoundment (Case A, Table III). About one-third of these sites are
within one mile of a water supply well which would be in the path of
any contaminated ground water flowing from these industrial sites
(Case B, Table III).
For the other categories, Table II and III present the analyses as
portrayed for the industrial category above.
Silka, Brasier
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TABLE II
Sunmary Statistics
for Waste Impoundment Characteristics
Category % Lined
Industrial 28
Municipal 23
Agricultural 16
Mining
Non-Coal 23
Coal 14
Oil & Gas
Brine Pits
10
Average Extrapolated Average Extrapolated
Area per Total Influent Total
Impoundment Impoundment Volune Influent
(Acres) Area (GPD) per Volume
(Acres) Impoundment (GPD)
16.7
3.0
2.3
68.6
6.0
5.6
430,000 2.1 Million 54 Billion
108,000 0.2 Million 9 Billion
43,000 3.1 Million 58 Billion
276,000 1.5 Million 6 Billion
122,000 0.3 Million 7 Billion
364,000
26,000
2 Billion
Silka, Brasier
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TABLE III
Summary Statistics
for Ground-Water Contamination Potential
of Waste Impoundments
Category
% in Case A % in Case B
Mining
Non-Coal
Coal
Oil & Gas
Brine Pits
27
11
5
1
% With % With a High
Ground-Water Waste Hazard
Monitoring Potential
Wells * Note
Industrial
Municipal
Agricultural
30
33
23
10
12
6
9
6
1
51
13
3
12
2
35
96
98
Case A : Ihose impoundments which are unlined, over usable aquifers
with virtually no protection from infiltration of
contaminants to the ground water.
Case B : Same as Case A with the addition that a water supply well is
within 1 mile and potentially in the path of any
ground-water contamination from the impoundment.
* Note : Potentially Hazardous Waste is not related to the Hazardous
Waste Management System Program regulations (40CFR Part
260-265). The waste hazard potential was assessed on
industry-wide basis using the following parameters:
Toxicity, persistence, mobility and intensity of
application.
Silka, Brasier
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SUMMARY
Preliminary findings of the Surface Impoundment Assessment conducted
by the Environmental Protection Agency indicate that, in the
industrial category alone, there are almost 11,000 sites containing
about 25,000 impoundments utilized for the storage, treatment or
disposal of liquid wastes. A significant portion of these, about
5,000 to 6,000, may contain potentially hazardous wastes. Very few
are reported to have a liner (less than 30%), and virtually no
monitoring of ground-water quality is conducted to detect
contamination beneath the sites. Furthermore, almost one third have a
high potential to contaminate usable aquifers, and a third of these
may possibly endanger water supply wells.
Similar analyses applied to information collected on impoundments used
for municipal, agricultural, mining, and oil and gas brine waste
liquids also indicate a lack of proper siting, design and monitoring
to prevent ground-water contamination.
Because of their proximity to population centers, both industrial and
municipal waste impoundments have the potential to directly affect
human health. While waste impoundments associated with agriculture,
mining and oil and gas may not have the same potential to affect human
health on the same scale as the industrial and municipal categories,
they do have the potential to eliminate ground-water resources for
other uses such as irrigation and stock watering.
Silka, Brasier
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