A demonstration of a Passive Reactive Berm (PRBerm) was conducted at a 10-meter M-60 tube-type machine gun range located at Charleston Air Force Base (CAFB), South Carolina, in 2009. The PRBerm technology consisted of silicate mineral sand that was amended with pH buffers and/or phosphate-based compounds that react with lead to form stable precipitates. The amendments were designed to buffer the soil pH within the berms and minimize the potential for off-site transport of lead in stormwater and groundwater through reduced solubility. Chemical amendments (e.g., phosphates) and high surface area materials reacted with lead and other heavy metals to reduce soluble lead concentrations (<0.45 micron) via precipitation, sorption, and complexation. Additionally, the technology was designed to reduce heavy metal leachability in impact berm soils such that they could pass Toxicity Characteristic Leaching Procedure (TCLP) action limits and be disposed of as non-hazardous waste at the end of the range life cycle.

This project will assess the performance of the field demonstration design and evaluate its long-term effectiveness in achieving post remedial actions and in reducing human health and/or environmental risk. The specific objectives of this effort are to evaluate temporal soluble lead concentrations in inert sand and cells treated with chemical amendments; to study the kinetics of metal release as a function of aging, weathering/oxidation, and surface area to mass ratio of metal fragments; and to investigate changes in metal mobility over time in studies designed to evaluate long-term stability of phosphate-treated soils.

The performance assessment will evaluate runoff and leachate waters and berm material through multiple analytical observation techniques. A major focus of this effort is to validate best management practices for metals stabilization with phosphate amendments and answer questions regarding the long-term stability of the approach under varying environmental conditions. Long-term performance data and evaluations of the conditions that foster or limit the long-term performance of different technologies will be interpreted. Once the assessment is complete, site parameters and environmental conditions will demonstrate the appropriate ranges of criteria necessary for characterizing, testing, designing, and monitoring such sites. Contaminants, associated chemicals of concern, and contaminant distribution may differ among small arms firing ranges (SAFRs); however, many characteristics of a site necessary to determine the efficacy of lead remediation technologies are similar.

This performance assessment will use the latest technology to evaluate the performance of the existing structures at CAFB through several tasks: (1) collect a minimum of 6 months of runoff and leachate waters from the lysimeters to evaluate the current leaching characteristics of the SAFR while gathering historical shooting records for the range to determine the amount of bullets fired into the SAFR; (2) take extensive samples from the SAFR to determine the mineralogical characteristics of the SAFR and the potential stability of the bullets and bullet fragments that have been fired into the berm; and (3) remove and sieve the existing bullets from the sand and place the sand back into the SAFR, then collect an additional 3-6 months of runoff and leachate waters to evaluate if there is any disturbance from the removal process.

This post remediation assessment will lead to an improved understanding of the permanence of phosphate treatments for SAFR soils and cost-effective improvements in how such soils are treated and/or managed after treatment. The project also will assist the Department of Defense with developing a consistent approach to previous field demonstration evaluations and deployment of PRBerms. (Anticipated Project Completion - 2018)