United States
Environmental Protection
Agency
Environmental Research
Laboratory
Athens GA 30605-2720
Research and Development
EPA/600/SR-93/082 June 1993
Project Summary
A Subtitle D Landfill Application
Manual for the Multimedia
Exposure Assessment Model
(MULTIMED)
Susan Sharp-Hansen, Constance Travers, Paul Hummel, and Terry Allison
The MULTIMED computer model
simulates the transport and transfor-
mation of contaminants released from
a hazardous waste disposal facility into
the multimedia environment. This re-
port is an application manual for the
use of MULTIMED In modeling Subtitle
D land disposal facilities (as described
in the Resource Conservation and Re-
covery Act). For Subtitle D facilities,
only the flow and transport components
of MULTIMED are used in simulating
leachate movement through the unsat-
urated zone and transport in the satu-
rated zone. A preprocessor guides the
user In the creation of a correct Sub-
title D input file by restricting certain
options and parameters and by setting
appropriate defaults. Instruction is pro-
vided for inexperienced as well as ex-
perienced model users who seek to
study or design waste disposal facili-
ties.
This Project Summary was devel-
oped by EPA's Environmental Research
Laboratory, Athens, GA, to announce
key findings of the research that Is fully
documented In a separate report of the
same title (see Project Report ordering
Information at back).
Overview
The Multimedia Exposure Assessment
Model (MULTIMED) simulates the move-
ment of contaminants leaching from a
waste disposal facility. The model in-
cludes two options for simulating leachate
flux. Either the infiltration rate to the un-
saturated or saturated zone can be speci-
fied directly or a landfill module can be
used to estimate the infiltration rate. The
landfill module is one-dimensional and
steady-state, and simulates the effect of
precipitation, runoff, infiltration, evapo-
transpiration, barrier layers (which can
include flexible membrane liners), and
lateral drainage.
To enhance the user-friendly nature of
the model, separate interactive preprocess-
ing and postprocessing software have
been developed for use in creating and
editing input and in plotting model output.
The pre- and postprocessors, PREMED
and POSTMED, have not been integrated
with MULTIMED because of the size limi-
tations of personal computers. Therefore,
after using the preprocessor to create or
modify input, the model is run in batch
mode. Afterwards, the postprocessor can
be used to produce plots of the Monte
Carlo output or plots of concentration ver-
sus time for transient output.
Subtitle D Applications
Some restrictions apply in the applica-
tion of MULTIMED to Subtitle D facilities.
These restrictions were made in an effort
to develop a conservative approach for
simulating leachate migration. First, only
saturated and unsaturated modules may
be used. Second, only steady-state or
transport simulations are allowed. Third,
no decay of the source term is allowed;
the concentration of contaminants enter-
ing the aquifer system must be constant
in time. Fourth, the receptor must be lo-
cated directly downgradient from the facil-
ity so that it intercepts the center of the
contaminant plume. Fifth, the contaminant
concentration must be calculated at the
top of the aquifer.
Thus, MULTIMED can be applied at
many Subtitle D land disposal facility sites
to simulate the transport of contaminants
from the source, through the saturated
and unsaturated zones, to a receptor well.
When MULTIMED is used in conjunction
with a separate source model, such as
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HELP, it can be used in a variety of appli-
cations. These applications include (1)
development and comparison of the ef-
fects of different facility designs on ground-
water quality, (2) prediction of the results
of different types of "failure" of the landfill,
and (3) prediction of the fate of the con-
taminants in the subsurface if leachate
migration into the groundwater below an
existing waste disposal facility occurs.
MULTIMED is not appropriate for all sites,
however. Care should be taken to assure
that the model is used appropriately.
MULTIMED can be used in the design
process to demonstrate that a particular
configuration will adequately prevent con-
taminant concentrations in groundwater
from exceeding health-based thresholds.
In other words, MULTIMED combined with
a source model can be used to demon-
strate that either a landfill design or the
specific hydrogeologic conditions present
at a site will prevent the migration of sig-
nificant quantities from the landfill.
In applying MULTIMED at a Subtitle D
Facility, the user must (1) collect
site-specific hydrogeologic data, (2) deter-
mine the contaminant to be simulated and
the active modules in MULTIMED and the
point of compliance, (3) propose a landfill
design and determine the corresponding
infiltration rate, (4) run MULTIMED and
calculate the dilution attenuation factor,
and (5) determine whether the design is
acceptable based on the resulting dilution
attenuation factor.
This application manual for the
MULTIMED model and pre- and
postprocessors, PREMED and POSTMED,
is designed to be used by inexperienced
as well as experienced users. Instructions
are suggested for two types of inexperi-
enced users—the "hands-on, learn-as-you-
go" user and the "read the document first"
user. An experienced user is defined as
one who is already familiar with the basic
capabilities and operational aspects of
PREMED, MULTIMED, and POSTMED,
and wants to use the programs to perform
simulations.
Obtaining MULTIMED Software
The MULTIMED computer code may
be obtained by sending a request to
Model Distribution Coordinator, Center
for Exposure Assessment Modeling, En-
vironmental Research Laboratory, U.S.
Environmental Protection Agency, Ath-
ens GA 30605-2720. Please include ei-
ther five 5.25-in (double-sided, double
density, DS/DD 360KB) diskettes or two
3.5-in (double-sided, high-density, DS/HD
1.44MB, error free) diskettes. The
MULTIMED code will be copied to your
diskettes and returned to you. Model
documentation is also available by send-
ing two 3.5-in diskettes (DS/HD). A hard
copy of the documentation is available
from the National Technical Information
Service (see box below).
Susan Sharp-Hansen, Constance Travers and Paul Hummel are with AQUA
TERRA Consultants, Mountain View, CA; Terry Allison is with Computer Sci-
ences Corporation, Athens, GA.
Gerard F. Laniak is the EPA Project Officer (see below).
The complete report, entitled "A Subtitle D Landfill Application Manual for the
Multimedia Exposure Assessment Model (MULTIMED)," (Order No. PB93-
185536; Cost: $36.50), 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
Athens, GA 30605-2720
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-93/082
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