Skip to Main Content U.S. Department of Energy

The MEPAS software is an essential tool for researchers assessing the impact to the environment and public from active and inactive release sites. The software integrates transport and exposure pathways for chemical and radioactive releases to determine their potential impact on surrounding environment, individuals, and populations. Thus, the "Multimedia" in Multimedia Environmental Pollutant Assessment System refers to multiple environmental transport media.

MEPAS is a physics-based approach, coupling contaminant release, migration and fate for environmental media with exposure routes and risk/health consequences for radiological and non-radiological carcinogens and non-carcinogens. MEPAS takes the nontraditional approach of combining all major exposure pathways into a multimedia computational tool.

MEPAS provides a WindowsTM-based user interface for setting up cases and analyzing results. This interface provides:

  • On-line help
  • Units conversions
  • Pictorial depiction of Conceptual Site Model
  • Ability to reference all data
  • Ability to edit most default parameters
  • Graphical views of input and output data

MEPAS's versatility and sound technical basis make it applicable for a wide range of multimedia transport and consequence analysis. As a result, MEPAS is used extensively by universities, government agencies, and domestic and international commercial firms.

MEPAS has undergone numerous external and internal evaluations during its development and subsequent applications. These reviews by the scientific community have fostered and confirmed the validity and usability of MEPAS. 
Major Applications
  • DOE Environmental Survey (1987-1990)
  • Hanford single-shell tank analysis/prioritization for tank characterization (1987-1990)
  • State of Washington Risk-Based Standards (1990)
  • Office of Management and Budge Pilot Study (performed by Oak Ridge National Laboratory at selected DOE sites)(1991)
  • Hanford 100-Area study of groundwater plume risk maps (1992)
  • Fate/transport modeling at U.S. Air Force bases (1992)
  • DOE Programmatic Environmental Impact Statement (1992-1993)
  • Hanford Remedial Action - Environmental Impact Statement (1994)
  • Baseline Environmental Management Report (1995)
  • Waste Isolation Pilot Plant Disposal Phase Final Supplemental EnvironmentalImpact Statement (1996-1997)
Major Evaluations
  • DOE selects MEPAS for environmental survey (1986)
  • EPA tests RAPS/MEPAS for prioritization (1987)
  • National Academy of Sciences reviews MEPAS (1989)
  • Idaho National Engineering Laboratory selects MEPAS for risk screening (1989)
  • Health and Welfare, Canada, selects MEPAS for use after reviewing 22 multimedia models (1992)
  • Hanford selects MEPAS for DOE Spent Nuclear Fuels Environmental Impact Statement (1993)
  • EPA Multimedia Model Benchmarking (1995)
  • International Multimedia Model Benchmarking (1995-Present)

Source Term Features
  • Mass balance
  • Mass partitioning
  • Active sites
  • Inactive sites
Fate and Transport Media
  • Air
  • Soil
  • Ground water
  • Surface water
Exposure Route Options
  • Inhalation
  • Ingestion
  • Dermal contact
  • External dose
Chemical Database
  • 500+ contaminants
  • Radionuclide
  • Inorganic chemicals
  • Organic chemicals

More information is available on the MEPAS Documentation Web site.