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Environmental Protection Agency NAS Overview  

The Natural Attenuation Software (NAS) is a graphical user interface for estimating the time required to achieve site-specific goals at sites contaminated with either fuels or chlorinated solvents. NAS requires the user to enter site characterization data to calculate the natural attenuation capacity (NAC) of various contaminants at a site. The user can use the NAC to evaluate the effects of source reduction or complete removal in terms of meeting a user-specified contaminant concentration at a specific point of compliance.


NAS Home Site
  • Visualization
  • Remedial Process Selection
  • Analytical Modeling
  • Numerical Modeling
  • Input
  • Tabular File: NA
  • Graphical File: NA
  • Output
    • Tabular File: NA
    • Graphical File: *.xls
    • Print Report: Yes
    • Chlorinated Solvents
    • Petroleum
    • Groundwater
    Technical Team Members
    • General technical staff familiar with chemical fate and transport
    NAS - data loading
    • Data must be entered manually.
    NAS - graphic loading
    • Not applicable. Graphical display is created within the program.
    NAS - logical flow
    • Step-by-step windows guide the user through data entry, including source data, water chemistry, and site information.
    • User can switch from user input to graphical interface to display data and results.
    NAS - expert knowledge
    • Extensive, site-specific background data are required to enter all the necessary parameters for the model to work
    • Understanding of water chemistry and how the analytical parameters relate to natural attenuation is recommended.
    NAS - functionality
    • Can be used to model natural attenuation for both chlorinated solvents and petroleum products.
    • Separate windows are used to enter model parameters. The user can switch between the data entry windows and graphical interfaces to iteratively change input parameters and view model results.
    • Detailed information on water chemistry for the site must be available for the model to work. The program does not provide default values for missing information, so the user must have expert knowledge about the average values.
    • User can enter regulatory cleanup values and a downgradient point of compliance; the model will calculate the amount of time required for a source to decay until the plume concentrations are below regulatory cleanup levels at the compliance point. The program displays this information in a tabular and graphical format.
    • The user can provide a source term that consists of a nonaqueous phase liquid (NAPL).
    • A numerical model (SEAM3D) is incorporated in NAS to estimate the Time of REmediation (TOR) for the plume. It should be noted, however, thatthe parameter information and observed data can only be specified along the plume centerline (i.e., in one dimension).
    • The user can create custom reports showing all user input data and model results.
    NAS - documentation
    • The users manual explains the windows and user-required inputs; however, it does not provide any background information about the parameters and why they are used.
    • No help files; user must refer to the users manual.
    • A user-group e-mail list is provided on the website. The user group is a resource for help with troubleshooting problems and asking questions.
    NAS - output
    • Limited output capabilities. NAS provides a report of user data and modeled outputs.
    NAS - sources
    • Version 1.30 downloaded November 17, 2004.
    • Users Guide.
    • Website offers tour of software via a PowerPoint presentation.
    • Examples.
    Note that this DST matrix is under active construction. Comments and suggestions about the structure
    or content of this website should be sent to Mike Adam .
    This web site contains technology information from private contractors and government agencies and is for informational purposes only. EPA cannot guarantee the accuracy or completeness of the data. Reference to any specific commercial product, process, or service, by trade name, trademark, manufacturer, or otherwise, does not constitute or imply the endorsement, recommendation, or favor of the United States Government.