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Model Report


Last Revision Date: 10/06/2009 View as PDF
General Information Back to Top
Model Abbreviated Name:

Model Extended Name:

Model Overview/Abstract:
The determination of concentrations of natural radioactivity in public water supplies begins with the measurement of the gross alpha particle activity. The gross alpha activity measurement is used as a screening technique. The gross alpha particle activity measurement may be substituted for the required Ra-226 and Ra-228 analysis provided that the measured gross alpha particle activity does not exceed 5 pCi/l at a confidence level of 95%. If this condition is met the source would be in compliance. If the gross alpha particle activity is greater than 5 pCi/l, the maximum contaminant level (MCL) may be exceeded.

The GARR program is of the "expert system" type and follows a Boolean logic decision scheme where the laboratory radionuclide analysis for gross alpha activity is compared with the MCL to determine if compliance exists or if additional laboratory analyses for specific radionuclides might demonstrate compliance. The decision scheme or "tree" is shown in the printed user's instructions and in the file DEC_TREE.TXT. This file is ASCII characters and may be viewed or printed.

This program is based on the Interim Primary Drinking Water Regulations; Radionuclides: published in the Federal Register July 9, 1976. It is not a substitute for these regulations.

Model Technical Contact Information:
Stan Rydell, Ph.D.
U.S. EPA, Region 1
Telephone: (617)-918-1637

The model was developed and is maintained by Dr. Stan Rydell.

User Information Back to Top
Technical Requirements
Computer Hardware
PC with 64 MB RAM and 1GB ROM (preferred).
Compatible Operating Systems
MS-DOS version 3.x or higher
Other Software Required to Run the Model
Fortran 90, Compiled Quick Basic 4.5
Download Information
The model is publicly available from U.S. EPA, Region 1
Using the Model
Basic Model Inputs
More complex model with greater input requirements, but no substantial modular or sub-model components.
User Support
User Qualifications
User needs high level of technical education and/or modeling experience. This program is for engineers and water treatment people experienced with ion exchange. Not suited for use by the general public.

Model Science Back to Top
Summary of Model Structure and Methods
The model uses fixed units (U.S.).

Governing equations are solved numerically.

Model Evaluation

Code verification has been performed in U.S. EPA Region 1.

Model has been internally peer reviewed (U.S. EPA Region 1) and externally peer reviewed.

Model uses software Beta testing.

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