FIRING RANGE ENVIRONMENTAL IMPACT–A CASE STUDY OF CAMP EDWARDS, MA

The National Guard Bureau is conducting an extensive investigation of Firing Ranges at Camp Edwards, Massachusetts to characterize the nature and extent of possible soil contamination and its potential impact on groundwater. The Impact Area has been used since the early 1900s for artillery and mortar training. Over 2000 soil samples have been collected along with the installation of over 300 monitoring wells. Several explosive compounds were found in soil and groundwater, primarily hexahydro-1,3,5- trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7- tetrazocine (HMX). The highest concentration of explosives was found in shallow soil samples collected immediately adjacent to targets. Indirect evidence from soil samples and laboratory experiments suggests the depositional form of the explosive is as a particulate. The source term for particulate explosives appears to be the result of low and/or high order detonation of munitions. Another possible source term explored is unexploded ordinance (UXO). Key mechanisms identified in the fate of the explosives are the rate of dissolution of the particulates, degradation, and adsorption. Once the explosive particulates are dissolved RDX and HMX are rapidly transported through the unsaturated zone to groundwater. RDX and HMX have been found in groundwater beneath and downgradient of the Impact Area at Camp Edwards. Degradation and adsorption of RDX and HMX is minimal at the Camp Edwards site. Under low ionic strength waters and minimal organic carbon content RDX and HMX behave conservatively. In contrast, 2,4,6-trinitrotoluene (TNT) is more strongly absorbed to the soil and undergoes rapid degradation in the soil and in solution resulting in minimal groundwater contamination.