Results of the Independent Verification and Validation Study for the D2-Puff Model

Abstract : The D2-Puff atmospheric dispersion model was developed for use in estimating the downwind hazards resulting from accidental releases of toxic chemicals at U.S. Army chemical munitions storage depots. D2PC, the only model currently accredited for that purpose, assumes flat terrain and steady-state meteorological conditions. D2-Puff is intended to extend the D2PC methodology to complex terrain and variable meteorology in a user-friendly computer code. The independent verification and validation (IV&V) study of D2-Puff Version 2.0.6 focused on these accreditation requirements and the implicit requirement that the model provide safe-sided hazard estimates. The conclusion of the independent verification is that D2-Puff correctly implements the D2PC methodology in a convenient and easy-to-use computerized model that fully satisfies all of the specified operational requirements. The conclusion of the independent validation is that D2-Puff is unlikely to underestimate downwind hazards in terrain typical of that found in the vicinity of chemical depots. However, D2-Puff is likely to overestimate the time that it will take for a toxic cloud to travel more than a few kilometers downwind because the model does not consider the height variation of wind speed.