CENTER FOR
EXPOSURE ASSESSMENT MODELING
Robert B. Ambrose, Jr., P.E.
Manager
Center for Exposure Assessment Modeling
Office of Research and Development
U.S. Environmental Protection Agency
Athens, GA 30613
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Center for
Exposure
Assessment
Modeling
(CEAM)
The Center for Exposure Assessment Modeling (CEAM) was
established in July 1987 to meet the scientific and technical
exposure assessment needs of EPA's Program and Regional
Offices and of State environmental agencies. CEAM is the
Agency designated Technical Support Center for Ecological
Risk Assessment. The Center is also the focal point for a
variety of general Agency support activities related to the
scientifically defensible application of state-of-the-art
exposure assessment technology for environmental risk-based
decisions. CEAM provides exposure assessment technology,
training and consultation for analysts and decision-makers
operating under various legislative mandates, including
FIFRA, CWA, TSCA, RCRA, SDWA, and Superfund.
Distribution
of Model
Codes and
Manuals
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Training |
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Model I —
Applications j
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Expert |
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Solving j
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In-depth
Participation
in Planning
and Conducting
Priority
Projects
CEAM Offers
Direct Support
To support the Agency and States in environmental risk-based
decisions concerning protection of air, water, and soil, CEAM
seeks to expand the expertise of persons who quantitatively
evaluate pollutant exposure as part of human and ecological
risk assessments.
CEAM is organized to:
o Assist in site-specific problem definition and provide
appropriate predictive techniques for accessing organic
chemicals and metals exposure through single and multi-
media pathways.
Maintain the Superfund Ecological Risk Technical Support
Center and provide training and assistance to regional and
headquarters Superfund staff in exposure and EcoRisk
assessments.
Maintain a distribution center for continually updated
models (codes and documentation) and databases for the
user community, including consultants; keep users up to
date through user group meetings, a newsletter, and a
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computer "bulletin board.
Offer 2- to 5-day training sessions at regional sites,
headquarters, and the Athens facility using instructors
from CEAM, the Center for Environmental Research informa-
tion, the EPA Training Institute, universities, and
consulting firms. Longer term (weeks, months, year)
on-the-job training at CEAM for individuals is also
available.
Provide requested assistance through "expert witness"
testimony, exposure calculations and assessments for
especially difficult or unusual scenarios, peer review of
exposure and EcoRisk assessments, and in-depth support for
high priority Agency projects.
Assist in conducting exposure and ecological risk assess-
ments for the complete range of EPA needs as part of RCRA,
TSCA, FIFRA, and CWA.
CEAM
Provides
Research
Expertise
Exposure assessment expertise is available for multimedia
modeling of organic chemical and heavy metal pollutant fate;
regional and local air contaminant modeling; source and site
characterization, monitoring, and measurement; marine and
estuarine pollutant fate modeling; pollutant dose-response
modeling; ecological impact and ecological risk assessment.
This expertise is drawn from the CEAM and associate staff at
the Environmental Research Laboratory, Athens, GA (ERL-
Athens), plus experts at affiliated laboratories including
the Environmental Research Laboratory, Duluth, MN (ERL-
Duluth); the Environmental Monitoring Systems Laboratory,
Las Vegas, NV (EMSL-Las Vegas); tho Environmental Research
Laboratory, Narragansett, RI (ERL-Narragansett); the Atmo-
spheric Sciences Research Laboratory, Research Triangle Park,
NC (ASRL); the Environmental Research Laboratory, Gulf
Breeze, FL (ERL-Gulf Breeze); the Environmental Monitoring
Systems Laboratory, Research Triangle Park, NC (EMSL-RTP);
and the Environmental Monitoring and Support Laboratory,
Cincinnati, OH (EMSL-Ciricinnati).
Multimedia Exposure Assessment--ERL-Athens develops aquatic
and terrestrial exposure models and measures or estimates the
physical, chemical, and biological properties (rate and equi-
librium constants) that are needed for model operation.
Environmental decision-making tools include pollutant fate
and exposure models; conventional pollutant loading and eco-
system response models; knowledge-based expert systems;
multimedia assessment, management, and control strategy
development and evaluation methodologies; and procedures for
conducting uncertainty analysis. Models are applicable to
watersheds, surface and ground waters, agricultural areas,
hazardous, waste sites, spill sites, water treatment plants,
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wildlife habitats, etc.
Air Models--ASRL-RTP conducts research on chemical, physical,
and meteorological processes in the environment and develops
models to relate pollutant source emissions to air pollutant
concentrations at receptor sites and wet- and dry-fall source
inputs to land and surface water.
Marine and Estuarine Exposure Models--ERL-Narragansett
develops exposure assessment methodologies for quantifying
transport and transformation of pollutants in marine and
estuarine environments.
Dose-Response Mocitjls—ERL-Duluth provides expertise in
predicting exposure within and impact on aquatic organisms
(dose response), and physiologically based pharmacokinetic
models of intoxication processes relating adverse effects on
a target organ to the external concentration profile.
Estuarine Effects—ERL-Gulf Breeze provides expertise for
predicting the lethal and sublethal impact of exposure to
toxic chemicals on pesticides in coastal, estuarine, and
marine environments, including effects on individual
components and ecological structure and function and the
resiliency of populations, communities., and ecosystems.
Monitoring and Measurement Methods—EMSL-Las Vegas designs
and conducts remote sensing and field sampling studies and
operates monitoring systems to characterize sources and sites
for modeling assessment.
Monitoring and Measurement Methods—EMSL-Cincinnati develops
analytical methods for the measurement of toxic materials in
municipal and industrial wastewaters, ambient waters, solid
waste, and Superfund samples.
Air Monitoring—EMSL-RTP develops monitoring systems for
measuring air pollutants and determining exposure in ambient
air, in indoor air, near toxic waste sites, and conducts
special air monitoring studies to assess atmospheric
pollution problems and evaluate exposure models.
CEAM Staff Mr. Robert B. Ambrose, Jr., P.E, - CEAM Manager
404-546-3130 Surface Water Quality
FTS 250-3130 and Pollutant Modeling
Aquatic EcoRisk
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Dr. James L. Martin, P.E.
Environmental
Engineering
Surface Water Quality
and Pollutant Modeling
Mr. Kendall P. Brown
Chemical Engineering
Leaching Modeling
Metals Modeling
Mr. David Disney
Software Systems
Analysis
Model and Documentation
Distribution/Quality
Control.
Mr. Timothy Wool
Software Systems
Analysis
Water Quality Modeling
Engineering and Assessment
Dr. David S. Brown
Metals Modeling
Soil Science
Dr. Fred Fong
Mr. Thomas 0, Barnwell
Mass Transport Modeling
Numerical Analysis and
Chemical Engineering
Model Applications/
Expert Systems
Watershed and Nonpoint
Source Modeling
Mr. Robert F. Carsel
Leaching, Ground Water
Modeling
Environmental
Parameters,
Soil Properties,
Uncertainty Analysis
Dr. Steven C. McCutcheon, P.E.
Mr. Lee A. Mulkey
Sediment and Pollutant
Transport Hydro-
dynamics
Multimedia Modeling,
Terrestrial Exposure
and Risk,
Uncertainty Analysis
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Mr. Charles N. Smith
Field Sampling and Study
Design Model Testing,
Monitoring Equipment,
Uncertainty Analysis
Pollutant Identification and
Chemical Fate Data
Dr. James J. Ellington
Hydrolysis Rate
Constants
Partition Coefficients
Mr. Heinz P. Kollig
Reliability of Fate
Constants in
Literature
Computation of
Unreported
Constants
Dr. John M. McGuire
Identification of
Transformation
Products and Unknown
Pollutants
Dr. William C. Steen
Biological Transforma-
tion Rate Constants
Chemical and Biological
Transformation Processes
Dr. Chad Jafvert
- Sorption Processes
Dr. David L. Lewis
Biodegradation and
B ioaccumu1ation
Processes
Dr. Nicholas Loux
Metals Speciation and
Sorption to Aquifer
Surfaces
Dr. John E. Rogers
Anaerobic Biotrans-
forraation Processes
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Dr. Eric Weber
Chemical Properties,
Degradation Rates and
Products of Organic
Pollutants
Dr. N. Lee Wolfe
Hydrolysis and Reduction
Processes
Dr. Richard G. Zepp
Organic Photolysis and
Oxidation Processes
Ecological Risk Assessment
Dr. Lawrence A. Burns
- Wetlands Ecology
Dr. James Hill
- Aquatic Food Chain
Exposure Models
Ecological Risk
Assessment
Dr. Ray R. Lassiter
- Ecologicn.I Risk
Assessment Modeling
CEAM Models
Meet Analysts'
Needs
The modeling packages currently available through CEAM
were selected from many candidate models by experienced users
in EPA regulatory and regional offices and by the Center
staff. Selection criteria included model utility and effec-
tiveness, availability of adequate documentation, degree of
acceptance and application by users, and the Center staff's
experience with the model. A wide range of analysis tech-
niques is provided, from simple desk-top procedures
suitable for screening analysis through computerized
steady-state models to sophisticated, state-of-the-art
continuous simulation models. Supported models are available
for microcomputer and mainframe system applications.
WQA
A collection of formulas, tables, and graphs allows
planners to make preliminary assessments of surface and
ground water quality in large river basins. These desk-top
procedures are appropriate for hand calculators. The manual
includes a discussion of the environmental chemistry of syn-
thetic organic chemicals and metals; a chapter on waste
source estimation techniques; and simple methods for assess-
ment of pollutant fate in rivers, lakes, estuaries and ground
water.
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Stream analysis techniques are included for conservative
substances, water temperature, biochemical oxygen demand,
dissolved oxygen, total suspended solids, coliform bacteria,
nutrients, and toxic organic chemicals and metals. Lake
analysis procedures include thermal stratification, sediment
accumulation, toxic organic chemicals, phosphorus budget,
eutrophication potential, and hypolimnion dissolved oxygen.
Estuarine analyses include estuarine classification, tempera-
ture, biochemical oxygen demand, dissolved oxygen, turbidity,
sediment accumulation, and non-conservative substances.
Ground water procedures include aquifer characterization, the
ground water flow regime, pollutant transport processes,
methods for predicting the fate and transport of conven-
tional and toxic pollutants, and interpretation of results.
Documentation: Water Quality Assessment: A Screening Proce-
dure for Toxic and Conventional Pollutants in Surface and
Ground Waters. EPA/600/6-85/002a-c.
QUAL2E
Conventional pollutants in one-dimensional streams and
well-mixed lakes all modeled under steady state conditions.
The conventional pollutants include conservative substances,
temperature, bacteria, biochemical oxygen demand, dissolved
oxygen, nitrogen, phosphorus, and algae. QUAL2E is widely
used for waste load allocations and discharge permit deter-
minations in the United States and other countries. It has
a 15-year history of application and is a proven, effective
analysis tool. QUAL2E Version 3 incorporates several un-
certainty analysis techniques useful in risk assessment.
Documentation: The Enhanced Stream Water Quality Models
QUAL2E and QUAL2E-UNCAS. EPA/600/3-87/007. (4 diskettesjs
DYNTOX
A waste load allocation computer program uses a probabi-
listic dilution technique to estimate concentrations of toxic
substances or fractions of whole effluent toxicity. DYNTOX
performs three types of simulations — continuous, monte
carlo, and log normal — that, based on probabilities, can
aid in analyzing the frequency and duration of toxic concen-
trations from a waste discharge, DYNTOX considers dilution
and net first-order loss, but not sorption and benthic ex-
change. The net loss rate must be determined on a case-by-
case basis and should not be extrapolated to different
conditions of flow, temperature, solids, pH, or light.
Documentations Dynamic Toxics Wasteload Allocation Model
(DYNTOX). (3 diskettes)
MINTEQA1
A geochemical model calculates equilibrium aqueous
speciation, adsorption, gas phase partitioning, solid phase
saturation states, and precipitation-dissolution of 11
metals (arsenic, cadmium, chromium, copper, lead, mercury,
nickel, selenium, silver, thallium, and zinc). MINTEQA1
contains an extensive thermodynamic data base and six
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different algorithms for calculating adsorption. Proper
application of MINTEQA1 requires user expertise, because
kinetic limitations at particular sites may prevent certain
reactions even though they might be thermodynamically
possible. (5 diskettes)
Documentation: MINTEQA1, An Equilibrium Metal Speciation
Model. EPA/600/3-87/012.
EXAMS-II
A steady-state and dynamic model rapidly evaluates the
behavior of synthetic organic chemicals in lakes, rivers, and
estuaries. EXAMS-II is an interactive program that allows
the user to specify and store the properties of chemicals and
ecosystems, modify the characteristics of either (via simple
English-like commands), and conduct rapid, efficient evalua-
tions of the probable fate of chemicals. EXAMS-II simulates
a toxic chemical and its transformation products using
second-order kinetics for all significant organic chemical
reactions. EXAMS-II, however, does not simulate the solids
with which the chemical interacts. The concentration of
solids must be specified for each compartment; the model
accounts for sorbed chemical transport based on solids con-
centrations and specified transport fields. Benthic exchange
includes pore water advection, pore water diffusion, and
solids mixing. The latter describes a net steady-state
exchange associated with solids that is proportional to pore
water diffusion. (4 diskettes)
Documentation: Exposure Analysis Modeling System (EXAMS-II).
EPA/600/3-85/038.
SWMM
Urban runoff quantity and quality is comprehensively
simulated. All aspects of the urban hydrologic and quality
cycles are simulated including surface runoff, transport
through the drainage network, und storage and treatment
(including cost). Alternate techniques are available for
simulation in a sewer system—a kinematic wave procedure for
most problem assessment and a full-equation routing method
for surcharged systems. SWMM can be used both for single-
event and for continuous simulation. It has been used in a
planning context as well as for detailed design studies.
SWMM also has a long history of use for urban drainage
assessment and design. (4 diskettes)
Documentation: Storm Water Management Model, Version 4.
EPA/600/3-88/001.
HSPF
Watershed hydrology and water quality for both conven-
tional and toxic organic pollutants is simulated. HSPF
incorporates the watershed-scale ARM (Agricultural Runoff
Model) and NPS (Non-Point Source) models into a basin-scale
analysis framework that includes pollutant transport and
transformation in stream channels.
The model uses information such as the time history of
rainfall, temperature, and solar radiation; land surface
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characteristics such as land use patterns and soil
properties; and land management: practices to simulate the
processes that occur in a watershed. The result of this
simulation is a time history of the quantity and quality of
runoff from an urban or agricultural watershed. Flow rate,
sediment load, and nutrient and pesticide concentrations are
predicted. The program takes these results, along with
information about the stream network and point source dis-
charges, and simulates instream processes to produce a time
history of water quantity and quality at any point in a
watershed — the inflow to a lake, for example. HSPF in-
cludes an internal data base management system to process the
large amounts of simulation input and output. (6 diskettes)
Documentation: Hydrological Simulation Program—FORTRAN.
EPA/600/3-84/066.
PRZM The vertical movement of pesticides in unsaturated soil,
both within and below the plant: root zone, and extending to
the water table using generally available input data that are
reasonable in spatial and temporal requirements. The model
consists of hydrology and chemical transport components that
simulate runoff, erosion, plant uptake, leaching, decay,
foliar wash off, and volatilization (implicitly) of a pesti-
cide. Predictions can be made daily, monthly, or annually.
Documentation: User's Manual for the Pest.ici.de Root Zone
Model (PRZM). EPA/600/3-84/109 (2 diskettes)
WASP A generalized modeling framework simulates contaminant
fate and transport in surface waters. Based on the flexible
compartment modeling approach, WASP can be applied in one,
two, or three dimensions. WASP is designed to permit easy
substitution of user-written routines into the program
structure. Problems that have been studied using WASP in-
clude bioclujirdcal oxygen demand, dissolved oxygen dynamics,
nutrients and eutrophication, bacterial contamination, and
toxic chemical movement.
A variety of water quality problems can be addressed with
the selection of appropriate kinetic subroutines that may be
either selected from a library or written by the user.
Toxics WASP combines a kinetic structure adapted from EXAMS
with the WASP transport structure and simple sediment balance
algorithms to predict dissolved and sorbed chemical concen-
trations in the bed and overlying waters.
Eutrophication WASP combines a kinetic structure adapted
from the Potomac Eutrophication Model with the WASP transport
structure. ETJTR04 predicts dissolved oxygen, carbonaceous
biochemical oxygen demand, phytoplankton, carbon, and
chlorophyll a, ammonia, nitrate, organic nitrogen, and ortho-
phosphate in the bed and overlying waters. (3 diskettes)
Documentation: WASP4, a Hydrodynamic Water Quality Model for
Toxic and Conventional Pollutants. EPA/600/3-87/039.
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DYNHYD4
A simple link-node hydrodynamic model simulates variable
tidal cycles, wind, and unsteady inflows. It produces an
output file that can be linked with WASP4 to supply the flows
and volumes to the water quality model.
The Food Chain Model is an associated program that takes
the time and space-variable pollutant concentrations calcu-
lated from WASP4, and predicts uptake and distribution
throughout a user-described aquatic food chain. (w/WASP)
Documentation: WASP4, a Hydrodynamic Water Quality Model for
Toxic and Conventional Pollutants. EPA/600/3-87/039.
SARAH
A steady-state mixing zone model calculates acceptable
concentrations of hazardous wastes discharged to land dis-
posal or waste water treatment facilities!. For steady or
batch waste streams, SARAH considers the following concentra-
tion reductions: dilution and leas during treatment, initial
Gaussian mixing at the edge of a stream, lateral and longitu-
dinal diffusion in the mixing zone, sorption, volatilization,
Hydrolysis, and Bioaccumulation in fish. The user must
specify appropriate in-stream criteria for protection of the
aquatic community, and of humans through consumption of fish
and water. The benthic community is not presently con-
sidered. Treatment loss is handled empirically. The human
exposure pathways considered include ingestion of treated
drinking water and consumption of contaminated fish.
Documentation: SARAH, a Surface Water Assessment Model for
Back-calculating Reductions in Abiotic Hazardous Wastes.
EPA/600/3-86/058. (1 diskette))
FGETS
A toxicokinetic model simulates the bioaccumulation of
nonpolar organic chemicals by fish from both water and
tainted food. Both of these routes of exchange are modeled
as diffusion processes that depend upon physico-chemical
properties of the pollutant and morphological/physiological
characteristics of the fish. FGETS contains a moderately
sized database of allometric relationships for gill morphol-
ogy with which it can simulate the direct gill/water exchange
of organic chemicals for essentially any fish r:pecies, assum-
ing certain default values. FGETS also contains a limited
database of physiological/morphological relationships that
are used to parameterize food exchange. Presently, only food
exchange by salmonids is represented in tlie database.
However, this database is being expanded to centrarchids,
perchids, and cyprinids. In addition to simulating bio-
accumulation of organic toxicants, FGETS can also calculate
time to death from chemicals whose mode of action is
narcosis. This calculation is based on the existence of a
single, lethal, internal chemical activity for such
chemicals. (1 diskette)
Documentation: FGETS (Food and Gill Exchange of Toxic Sub-
stances): A Simulation Model for Predicting Bioaccumulation
of Nonpolar Organic Pollutants by Fish. EPA/600/3-87/038.
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Models in
Development
Several model development projects are underway to
provide additional modeling tools to support Agency
regulatory programs. The research and development programs
producing these models at the ERL-Athens include projects on
ecological risk assessment, land disposal of hazardous
wastes, and exposure assessment models for pesticides.
Multimedia Exposure Assessment Model for Hazardous Wastes
simulates the release and fate of hazardous waste constitu-
ents derived from land disposal systems. Soil (unsaturated
zones), atmospheric, ground water, and surface viater routes
are included. The model is implemented within a monte carlo
framework to facilitate uncertainty analysis as an integral
part of risk assessment.
Pesticide Ground Water Exposure Assessment Model provides
a linked system of models that combines root zone dynamics
(PRZM) with unsaturated-saturated zone transport and trans-
formation predictions for pesticides. The modeling package
combines one- and two-dimensional finite element codes and
enables simulation of a wide range of environmental
settings. This model is also implemented within a monte
carlo framework to facilitate uncertainty analysis.
Terrestrial Environmental Exposure Assessment Model
computes the distribution, movement, and potential ecological
impact of chemical pollutants released tc terrestrial envi-
ronments. Atmospheric transport and interactions within the
soil-plant-water complex are included.
Drinking Water Treatment Plants can be simulated by
combining the unit operations typically employed in designed
systems. This model uses chemical-specific data and mass
transport theory to estimate the exposure reductions achieved
by treating contaminated drinking water. Model capability
ranges from simple operations typical of small, rural water
supply systems to large-scale municipal system*!.
CEAM Services
Are Readily
Obtained
The Center also functions as a clearinghouse for correcting
code and routine errors or other problems that are discovered
as the techniques are applied. This vital information ex-
change function helps users obtain correct computations when
applying a model developed for one purpose to a new and
different problem. New software releases periodically
document code updates and corrections to problems identified
as the models are used. Model maintenance activities focus
on overcoming problems in the use of models; further develop-
ment, refinement, and extension of these models is a separate
research activity.
The Center periodically distributes, free of charge, a news-
letter to a large number of model users and developers in the
Agency, other federal, regional and state environmental
management agencies and their consultants, international
agencies, and private industry and academia. The newsletter
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provides helpful hints to model usars and communicates infor-
mation on scheduled workshops, model improvements and
developments, the availability of technical documents, and
planned meetings and conferences.
Consultation
For consultation or technical assistance on exposure or
EcoRisk assessment projects, write or call the CEAM manager,
Mr. Robert B. Ambrose, Jr.
CEAM
US E.P.A.
College Station Road
Athens, Georgia 30613
(404) 546-3130
or FTS 250-3130
For information about or assistance with CEAM models, write
to CEAM model support at the above address or call the CEAM
model support line at (404) 546-3549 or FTS 2,50-3549. You
may also correspond with us by using the CEAM electronic
bulletin board system as described below.
PC and
Mainframe
Models
The models are available from the CEAM at. no charge. Main-
frame versions of the programs compatible with DEC VAX
systems are available on standard one-half inch, 9-track
magnetic tape. When ordering tapes, please specify the type
of computer system that the model will be installed on (VAX,
PRIME, HP, CYBER, IBM, etc.) and whether the tape should be
non-labeled. If non-labeled, specify the storage format as
ASCII or EBCDIC. If the tape is for a DEC system, specify
the storage format as VAX Files-11 (ASCII). Requests for
PC versior.8 of the models should be accompanied by the appro-
priate number of double-sided, double-density (DS-DD), error-
free diskettes. To obtain copies of the models, please send
9-track specifications, or the appropriate number of disk-
ettes, to the attention of David Disney at the Center for
Exposure Assessment Modeling. Program and/or user documenta-
tion, or instructions on how to order documentation, will
accompany each response, in addition to installation
instrucitons.
Electronic
Bulletin
Board
The CEAM Electronic Bulletin Board Systems (B3S) is designed
to meet the increasing demand for exposure assessment models
supported by the Center. It provides more efficient communi-
cation between users and support staff, as well as immediate
acquisition of models by those users under extreme time
pressure. The CEAM BBS has been installed using a commer-
cially available software package. The BBS is available
7 days a week, 24 hours a day. The System Operator may be
paged through the BBS from 7:00 a.m. until 4:00 p.m. Monday
thru Friday for assistance.
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The services presently offered through the BBS are: 1. down-
loading of CEAM-supported simulation models; 2. Uploading of
user input data sets for staff review and problem solving;
3. listing of current activities and events, (such as
training courses) helpful hints about the models, and model
documentation; and 4. message area for discussion of computer
modeling problems and enhancements.
To access the CEAM BBS, call 404/546-3402 or FTS/250-3402 and
follow the interactive prompts. The communications para-
meters needed are 2400/1200 baud, no parity, 8 data bits, and
1 stop bit. To access the CEAM BBS via the EPA Dec Net, type
SET HOST ATHENS, USERNAME-BBS, PASSWORD-ATHENS. This will
allow access to the CEAM BBS without long distance charges.
Downloading of models and uploading of datasets is not
possible through Dec Net; however, the user will be able to
access the bulletin area and leave and/or read BBS messages.
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