An official website of the United States government.

We've made some changes to EPA.gov. If the information you are looking for is not here, you may be able to find it on the EPA Web Archive or the January 19, 2017 Web Snapshot.

ReachScan - an Exposure Assessment Model

ReachScan's status and availability

ReachScan is under development and is currently not available. It has not been peer reviewed in accordance with EPA Peer Review Guidance but will be scheduled for peer review upon completion of the web-based version. ReachScan was developed under contract by Versar Inc. for the EPA.

What does ReachScan do?

ReachScan will estimate chemical concentrations in single or multiple stream (segments) reaches by simple dilution or using simple fate algorithms. It will also estimate the number of days per year that an aquatic ecotoxicological concern concentration will be exceeded in the subject stream or stream segment. A chemical's aquatic ecotoxicological concern concentration is the estimated concentration at which the chemical may adversely affect aquatic organisms. ReachScan will provide stream flow statistics on a daily average basis. When available, ReachScan can be used to determine the presence of endangered species or critical habitats in the county of the releasing facility.

Using ReachScan

A web-based ReachScan is currently under development. ReachScan will operate as an integrated module in the web-based IGEMS system developed by the EPA, and will include the Probabilistic Dilution Model (PDM3).

To run ReachScan in the future, one will need the following information:

  • Facility information, such as:
    • National Pollution Discharge Elimination System (NPDES) number.
    •  Facility name.
    •  Standard Industry Classification (SIC) code.
  •  Reach number (an 11-digit number that identifies a specific section of a stream).
  •  Distance up- or downstream to consider.
  •  Amount of chemical released to stream.
  •  Chemical properties (if chemical fate is to be considered), including:
    •  Molecular weight, Solubility, Vapor pressure, Soil Adsorption Coefficient (Koc), Half-life.

EPA Technical Contacts

Wen-Hsiung Lee
US Environmental Protection Agency
Office of Pollution Prevention and Toxics
Risk Assessment Division
e-mail:lee.wen-hsiung@epa.gov

David Lynch
US Environmental Protection Agency
Office of Pollution Prevention and Toxics
Risk Assessment Division
e-mail:lynch.david@epa.gov