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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