Internal verification provides the main mechanism for non-independent evaluation and review of environmental models implemented by the Agency. It should include an examination of the numerical technique in the computer code for consistency with the conceptual model and governing equations. For more general information on how EPA develops and evaluates models, see the EPA document Guidance on the Development, Evaluation, and Application of Environmental Models. The linked copy includes some yellow highlighting of text used in this website for describing peer and verification reviews.

EPA guidance makes a distinction between multiple code verification by code developers and a potential independent testing of code, which is why this website make a distinction between internal and external verification. Independent testing of the code once it is fully developed can be useful as an additional check of integrity and quality.

The purpose of internal verification is two-fold:

• Translation of mathematical equations that constitute model framework into functioning computer code.
• Verification that the code has no inherent numerical problems while obtaining a solution.

Mechanisms of internal verification include:

• Extensive model research and interpretation.
• Mind mapping new model functionality amongst our team of programmers and environmental scientists.
• Writing computer code the execute new model functionality.
• Maintain documentation of models, parameters, and equations.
• Code verification to make sure the code performs according to model design specifications.

The SPRG calculator results were verified by Oak Ridge National Laboratory (ORNL) by conducting a comparison of calculator results to independent spreadsheets. Internal verification spreadsheets are presented here for workers and non-workers. In addition, since May 2019, every default land use and media combination in the calculator is programmed to run nightly. The results are compared against the previous night, and any changes to SPRGs are flagged for attention. Since August 2023, an automated link checking routine has been programmed to run nightly and flag any broken links. Additionally, independent manual link checking is performed on a quarterly basis to ensure comprehensive verification.

• March 2020

  For March 2020, the spreadsheets are divided into results that use secular equilibrium and those that do not use secular equilibrium. Each spreadsheet presents SPRG outputs for default exposure parameters with default isotope-specific inputs, state exposure parameters with default isotope-specific inputs, site-specific exposure parameters with default isotope-specific inputs, and site-specific exposure parameters with user-provided isotope-specific inputs. Outputs are presented below from the most recent calculator updates. Default and State include: resident and commercial worker for the default and state calculator outputs. Site-Specific and User-Provided include: resident and commercial worker for the site-specific and user provided calculator outputs.

  • March 2020, Default and State Specific, does not assume secular equilbrium
  • March 2020, Site Specific and User Provided, does not assume secular equilbrium
  • March 2020, Default and State Specific, assumes secular equilbrium
  • March 2020, Site Specific and User Provided, assumes secular equilbrium
  
  

• October 2015

  October 2015 Internal Verification Spreadsheet