Environmental Health - Toxic Substances Hydrology Program

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New Version of NAS (Natural Attenuation Software) Available

NAS (Natural Attenuation Software) has a user-friendly graphical interface that helps environmental professionals estimate how long it will take for natural attenuation processes to clean up contaminant plumes. The software can plot input data and simulation results to aid in decision making.

NAS (Natural Attenuation Software) is a software package that provides a decision-making framework for determining the time needed to clean up ground-water contamination sites. The package has been upgraded with the release of version 2.2.0. This new version:

  • compares times of cleanup associated with monitored natural attenuation to pump-and-treat remediation,
  • expands the kinds and numbers of contaminants considered, and
  • allows for concurrent consideration of solvents (chlorinated ethenes) and petroleum hydrocarbons.

NAS was developed by the U.S. Geological Survey (USGS), Virginia Polytechnic Institute and State University (Virginia Tech), and the U.S. Navy to help environmental cleanup professionals estimate how far plumes will migrate and how long natural attenuation processes will take to clean up contamination.

ESTCP Evaluation Project

The Environmental Security Technology Certification Program (ESTCP) is funding a project to evaluate NAS's ability to estimate cleanup times associated with combining the remediation of a contaminant source-area with the use of Monitored Natural Attenuation (MNA) to remediate the remaining downgradient contaminant plume. Project investigators are applying NAS to eight contamination sites across the Nation to test the software's predictive capability and the utility of the estimates it provides. ESTCP is a Department of Defense (DOD) program that promotes innovative environmental technologies through demonstration and validation projects at DOD contamination sites.

NAS Demonstration Sites

NAS Training Courses – Technology Transfer

The USGS and Virginia Tech have conducted a series of short courses on "Estimating Times of Remediation Associated with Monitored Natural Attenuation and Contaminant Source Removal." The courses are part of an effort by the USGS Toxic Substances Hydrology (Toxics) Program to provide or transfer the technology it develops to stakeholders that can benefit from the information and methods. These short courses on NAS present a decision-making framework and methodology for assessing MNA and estimating timeframes required for natural attenuation processes to lower contaminant concentrations to regulatory goals.

More Information


Chapelle, F.H., Widdowson, M.A., Brauner, J.S., Mendez, E., and Casey, C.C., 2003, Methodology for estimating times of remediation associated with monitored natural attenuation: U.S. Geological Survey Water-Resources Investigations Report 03-4057, 51 p.

Mendez, E., Widdowson, M., Brauner, S., Chapelle, F., and Casey, C., 2004, Natural attenuation software (NAS)—A computer program for estimating remediation times of contaminated groundwater, in Latini, G., Passerini, G., and Brebbia, C., eds., Development and Application of Computer Techniques to Environmental Studies X: WIT Press, p. 185-194.

USGS Information on Environmental Simulation Models

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Page Last Modified: 27-Jun-2018 @ 07:15:35 PM EDT