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page title goes here Risk Assessment

DCC Internal Verification Record

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 DCC 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 below for workers and non-workers. OOnce the values are verified, the calculator is automatically checked every night for functionality and output verification using a python and selenium script that compares the new outputs for every decay output option with the previously verified outputs for the default, site-specific, and user provided options. The results of the most recent automatic verification can be found here. This automatic verification procedure has been used since October 2022. 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 DCCs 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.