Jeffrey A. Gerald

Modeling Fate of RDX at Demolition Area 2 of the Massachusetts Military Reservation

The movement of explosive RDX residue from soil to groundwater at Demolition Area 2 of the Massachusetts Military Reservation was studied with mathematical models to assess its utility and limitations and to determine requisite model improvements and data needs. The Munitions Residue Characterization and Fate model, which is based on the MEPAS source term model for soil modified for solid phase residue with dissolution, the MEPAS vadose zone model, and the MEPAS aquifer model were used in this study. All three models were applied within ARAMS™ to facilitate model-to-model connectivity for computing movement of RDX from soil to vadose zone, and from vadose zone to groundwater. Model parameters and a hypothetical RDX residue loading rate were adjusted to match model results to measured RDX concentrations in surface soil and in groundwater. Through an iterative process, a loading rate of 1 kg/yr for RDX residues applied for 10 years starting in 1978 was found to fit measured conditions 20 years later. Model results were sensitive to the C4-RDX dissolution flux rate and the aqueous RDX degradation rate. Results indicate that dissolution of C4 and degradation of RDX in soil and groundwater could be quite slow, and such processes warrant further study. Mechanistic models such as those presented will be useful for estimating fate of constituent residue in soil and transport to receiving waters for evaluating range residue carrying capacity and compliance issues.

Modeling Fate and Transport of Munitions Constituents on Firing Ranges

The Training Range Environmental Evaluation and Characterization System (TREECS™) computes the fate and transport of munitions constituents deposited on military firing/training ranges. TREECSTM was developed with two levels of capability, Tiers 1 and 2, where Tier 1 is for conservative screening assessments, and Tier 2 is for more accurate predictions. The models and associated processes for Tier 2 are described. Tier 2 was applied to ranges at Fort A.P. Hill, VA, for initial demonstration purposes. Observed field data were provided after model application and are compared to model-computed results. Although the comparison was not sufficient for model validation, it does demonstrate that the model leads to the same general conclusions that the field data provided.