United States
Environmental Protection
Agency
Office of Health and
Environmental Assessment
Washington DC 20460
Research and Development
EPA-600/S8-83-030 Jan. 1984
Project Summary
Rapid Assessment of Potential
Ground-Water Contamination
Under Emergency Response
Conditions
A. Donigian, T. Y. R. Lo, and E. Shanahan
This manual provides a methodology
for estimating potential ground water
contamination under emergency re-
sponse conditions at abandoned hazard-
ous waste or toxic chemical spill sites.
Specifically, this manual is designed for
use by field personnel who must esti-
mate quickly how contaminant concen-
trations change with time and distance
from an emergency response site. The
procedures include evaluation of critical
contaminant and site characteristics as
input to an assessment methodology
for analyzing the fate and movement of
chemicals through both the unsaturated
and saturated (i.e., ground water) soil
zones. A graphical technique (nomo-
graph) has been developed as an inte-
grated methodology for assessing con-
taminant movement through both the
unsaturated and saturated (ground
water) zone. Guidelines for evaluating
critical waste and site characteristics
are provided to allow estimation of
needed nomograph parameters.
This Project Summary was developed
by EPA's Office of Health and Environ-
mental Assessment, Washington, DC,
to announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The Comprehensive Environmental
Response, Compensation, and Liability
Act of 1980 established a national fund
for cleaning-up spills and abandoned sites
containing hazardous substances. When
these sites are discovered, EPA must
decide quickly if an urgent threat exists
requiring immediate action. This project
is intended to aid the Agency in making
these decisions by providing a method for
rapidly evaluating the human health and
environmental threat caused by dis-
charges to ground water. The Agency's
final decision must also consider the
threat caused by releases to the air and
surface waters. The EPA Exposure Assess-
ment Group hopes to eventually provide
similar methods which can be used to
assess the threats associated with the
other media as well.
The assessment procedures in this
manual are designed to allow emergency
response personnel to make a first-cut,
order-of-magnitude estimate of the poten-
tial extent of contamination from a waste
site or chemical spill within the 24-hour
emergency response time frame. These
procedures are not intended to provide a
definitive, in-depth analysis of the com-
plex fate and transport processes of
contaminants in the subsurface environ-
ment.
The primary goal of this manual is to
provide the basis for determining the
need for emergency actions such as
emergency sampling, containment/
removal, and drinking water restrictions
in order to preclude or minimize human
exposure from ground water contamina-
tion at an emergency response site. Two
specific emergency response situations
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are envisioned where the assessment
procedures in this manual would be
applied.
1. Discovery of an abandoned hazard-
ous waste site where an assessment
of the potential extent of the waste
plume is needed within the emer-
gency response time frame.
2. Spill (or leakage) of a toxic waste or
chemical where the potential for
ground water contamination and the
extent of contamination must be
assessed within the emergency re-
sponse time frame.
Time and resource limitation expected
during an emergency response have
required a number of simplifying assump-
tions in our assessment procedures;
additional simplifications may be needed
by the user due to limited data and
information available at a particular emer-
gency response site. The major assump-
tions incorporated into the assessment
procedures in this manual are as follows:
1. Homogenous and isotropic properties
are assumed for both the unsaturated
and saturated zones (or media).
2. Steady and uniform flow is assumed
in both the unsaturated and saturated
zones.
3. Flowandcontaminantmovementare
considered only in the vertical direc-
tion in the unsaturated zone and the
horizontal direction in the saturated
zone.
4. All contaminants are assumed to be
water soluble and exist in concentra-
tions that do not significantly affect
water movement.
two continuous inputs lagged by the pulse
duration.
Results
The nomograph (Figure 1) predicts
contaminant concentrations as functions
of both time and location in either the
unsaturated or saturated zone. Separate
computations, parameter estimates, and
use of the nomograph are required for
each zone. The prediction requires evalu-
ation of four dimensionless quantities
(Ai, A2, 81, and B2) and subsequent
evaluation of the result (C/Co) through
use of the nomograph. The parameters
required for this procedure are:
initial contaminant concentration
dispersion coefficient
average interstitial pore water velocity
degradation rate coefficient
soil bulk density
soil water content or effective porosity
partition coefficient
Extensive guidelines for evaluation of
these parameters are provided.
Methodology
The procedures developed in this model
are based on a one-dimensional transport
equation for flow through a porous
medium. The equation considers disper-
sion, advection, equilibrium adsorption
(linear isotherm) and degradation/decay
(first order kinetics). Analytical solutions
to the transport equation were presented
for both continuous (step function) and
pulsed inputs of contaminants. The pulse
solution was used to simulate short-term
releases such as might occur from a spill
or tank leak. The nomograph was de-
veloped from the continuous input solu-
tion but can also be used on pulse
problems by subtracting the solutions to
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0,2 0,4 0,6 0,8 1.0 1.2 1.4 1.6 1.8 "p_2 0 20_
I'lH'I'I'MM I i
-.j|-07|~0.5]-0.3|-0./
-3.00 -1.50-1.0-0.8-0.6-0.4 -0.2 0.0
Step 1: Enter AI
Figure 1. The rapid assessment nomograph.
:°-9 Enter B,
intiiiii ii in 1111 * iin
0.r|0.3J0.5| 0.7 I 0.9 \\ 1.1
0 0.2 0.4 0.6 O.8 1.0'
O.8
B,
Step 1: Enter fli
I I
1.3
1.2
Anthony S. Donigian, Jr.. T. Y. Richard Lo, and Edward W. Shanahan are with
Anderson-Nichols & Co.. Inc.. Palo Alto, CA 34303.
Lee A. Mulkey is the EPA Project Officer (see below).
The complete report, entitled "Rapid Assessment of Potential Ground-Water
Contamination Under Emergency Response Conditions," (Order No. PB84-133
123; Cost: $16.00. subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
College Station Road
Athens, GA 30613
wllS. QOVEWmENT PRINTING OFFICE 1984-759-015/7279
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United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use $300
• PS
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