Evaluation of atmospheric transport and dispersion models for suitability in a DHS chemical supply chain risk assessment

The Institute for Defense Analyses is conducting a multi-year study for the Department of Homeland Security's Chemical Security Analysis Center (DHS CSAC) to identify the most suitable atmospheric transport and dispersion (AT&D) modeling systems to support consequence estimation in a probabilistic assessment of the risk to human health from intentional releases of toxic industrial chemicals (TICs) within the national chemical supply chain. These systems must be able to support the estimation of acute human population health effects by predicting the AT&D following large, potentially catastrophic releases of TICs from chemical facilities and transportation vehicles. The suitability of several models for use in the risk assessment will be evaluated according to the models' operational characteristics, technical capabilities, and prediction accuracy.

This presentation discusses preliminary results of the evaluation a small set of models (CHARM, HPAC, PHAST, and TRACE) for suitability in the DHS CSAC risk assessment. These results include comparisons of model predictions of notional industrial chemical release scenarios and of selected releases from passive gas and dense gas dispersion field experiments. We also attempt to characterize some of the features and limitations of these modeling systems with respect to their ability to predict TIC AT&D for relevant release scenarios and produce relevant outputs for the chemical supply chain risk assessment.