Active hand grenade ranges have the potential to be contaminated with munitions constituents as a result of military training activities. The few studies that have been completed to date indicate that there is a high probability of contamination due to the extensive use of hand grenades at ranges, the relatively small area that these ranges cover, and the large amount of energetic compounds used. This project validated the long-term degradation of explosive contaminants and the immobilization of metal contaminants in active grenade range soil via topical lime addition. The effects of continued range use and precipitation also were assessed.
The demonstrated technology is based on the premises that increased alkalinity, caused by lime addition, will result in (1) significantly decreased water solubility of heavy metals present in the soils and (2) base-catalyzed transformation of explosives that will eliminate migration of RDX- and TNT-based explosives from the range area. Data and observations obtained from the treatability and field studies will be used to develop a best management practice for hand grenade ranges.
Application of lime can reduce munitions constituent migration in both surface water and leachate. A 77% reduction in RDX concentration was seen in pore water from the treated bay. Individual sampling events achieved greater than 80% reduction. The final surface water samples indicated that the RDX concentration was reduced by more than 96%, from the control. The extractability of iron, manganese, chromium, and vanadium from the grenade range soil decreased following lime treatment. The concentration of iron in the pore water was decreased 70% in the leachate from the treated bay, over the control. The extractability of zinc, lead, and nickel from soil was unchanged by the lime treatment. The most prominent metal in the surface water samples was zinc. The pH in the source zone could be maintained above 10.5 with quarterly applications. The pH outside the reactive zone was not significantly different from the control for the soil, the soil pore water, or the surface water runoff. Application of lime in hand grenade range bays requires only Level D personal protective equipment, modified by the addition of a particulate respiratory mask and, possibly, the substitution of goggles as protective eyewear. Lime application was accomplished easily within a few hours and did not require highly specialized tools and equipment. The cost of the lime is approximately $400 per application. Treatment does not produce any residuals, and monitoring consists of soil pH testing in and outside of the reactive area. The technology is affected by soil moisture and may not be appropriate in a dry climate unless irrigation is added to the treatment. Additional liming should be considered along with regularly scheduled range maintenance events. Together, the results indicate that lime addition can be an effective treatment for munitions constituents on ranges and that this method does not appear to pose adverse side effects to the surrounding environment if applied properly and monitored on a regular basis.
This cost-effective training area management strategy will help ensure the long-term viability of hand grenade ranges. Proactive management of grenade ranges will help to mitigate potential range closings that could significantly impair military training and mission readiness. The overall costs of soil remediation also will be reduced by providing a technology capable of eliminating contaminant migration, thereby reducing the volume of soil that will eventually need to be remediated. (Project Completion - 2007)