Prediction of Soil Contamination Resulting from Dry Vapor Phase Chemical Agent Deposition

The U.S. Army is responsible for maintaining the protection of Army personnel, the
general population, and the environment at Army installations and surrounding communities
which may be impacted from an airborne release of chemical agent into the atmosphere
resulting from an accidental breach of chemical filled munitions. Rigorous safety and hazard
mitigation procedures are implemented with any recovery and destruction operation involving
handling of chemical filled munitions occurring at sites where chemical munitions have been
buried or stored to minimize the probability of a chemical release and resulting exposure.
While chemical releases are exceptionally rare, Recovery Sampling and Analysis Plans (RSAPs)
are required at some sites as part of emergency response plans established at Army
installations. RSAPs establish the procedure for the return of evacuated tenants at Army
Installations or residents within adjacent communities potentially impacted by chemical agent
contamination. Many RSAPs require intensive targeted sampling and monitoring of chemical
agents and degradation products capturing potential secondary pathways of exposure such as
contact exposure with surfaces or drinking water ingestion exposure in contaminated areas to provide a basis for the return of people displaced by chemical agent releases. Numerical prediction models calculating the initial state of potential chemical agent contamination across
the landscape is useful to define the targeted sampling and monitoring footprint potentially
impacted by dry vapor‐phase deposition of chemical agent.
Here, we present a model predicting soil contamination levels from deposition of vapor
phase chemical agent occurring from fallout of chemical agent released to the atmosphere.
The model is based on a combination of U.S. Army D2 plume dispersion model, subsequential
mass balance considerations serving as the basis of the deposition calculation, and site ‐specific
soil properties such as soil bulk density to arrive at the prediction of soil contamination level.
The deposition piece of the soil contamination model is compared to other accepted dry gas
phase contaminant deposition models such as the modeling option included in the American
Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD). The
comparison of deposition predictions in both the U.S. Army D2 model and AERMOD reveals a
similarity in results.