The objectives of this technology demonstration were to assess the environmental benefits, feasibility, and cost of using sand as a deceleration medium in small arms firing range (SAFR) berms in conjunction with amendments designed to retard the migration of lead (Pb) into the surrounding environment. The amendments provide for reduction of Pb solubility through potential hydrogen (pH) buffering of pore fluids within the SAFR berm, as well as the sequestration of Pb through surface adsorption and the precipitation of insoluble Pb salts. This technology application is known as a Passive Reactive Berm (PRBerm™). The purpose of this technology demonstration was to provide range operators with an economical means of controlling the off-site migration of Pb, while maintaining the benefits of sand as a deceleration medium. The PRBerm™ technology is applicable to new and existing ranges. In particular, this technology is designed to address sites where the native soils available for SAFR berm construction either lack the characteristics necessary to retard the migration of soluble Pb (e.g., acidic soils) or are susceptible to erosion and off-site transport of Pb as a result of their high clay content.

Technology Description

Replacement of easily suspended, clay-rich soil in the primary impact area with a material that has high hydraulic conductivity and a low potential for producing suspended solids was expected to drastically reduce the amount of the Pb currently leaving the site. By amending the berms with buffer and Pb immobilization amendments such as the TRAPPS™ amendment and the thermally treated fish bones (TTF), the amount of soluble and colloidal Pb in the surface water and the leachate water leaving the new berm will also be reduced. Both TRAPPS™ and the TTF have been used for Pb stabilization in analogous systems.

Treatability studies conducted at the Engineer Research and Development Center (ERDC) Vicksburg determined that an amendment ratio of 5% (weight/weight) to sand was sufficient to contain >90% of soluble Pb within the berm material. The technology was field tested on the SAFR (M-60 range) at Charleston Air Force Base (CAFB) in Charleston, SC. The CAFB PRBerm™ tested a 5% TRAPPS™ amendment (a granular, apatite-based material), alone and in combination with 5% TTF Apatite™. During the CAFB PRBerm™ field demonstration, storm water runoff and leachate water samples were collected and analyzed for metals, total suspended solids (TSS), and pH. At the conclusion of the study, the amended impact soils were analyzed for total and dissolved metals and metal leaching.

Demonstration Results

The results indicated that variation in the amount and type of rounds fired into berms has an effect on the Pb concentrations contained in leachate and runoff. The control lysimeter had the least amount of rounds fired into the impact area, which caused it to have the lowest Pb concentration. The lysimeter that was amended with 5% TRAPPS™ had the highest total Pb concentrations in both leachate and runoff. However, the inset lysimeter containing 5% TTF passed the regulatory limits for Pb, chromium (Cr), nickel (Ni), Arsenic (As), and antimony (Sb), which means that the soil could be disposed of in a nonhazardous waste landfill. Nonhazardous waste provides a low-cost disposal option as compared to hazardous waste. For the Toxicity Characteristic Leaching Procedure (TCLP) tests, there was a decrease seen in the concentration of Pb for the amended lysimeters when compared to the unamended lysimeter. Even though both amendments decrease Pb concentrations, the 5% TTF performed the best.

Implementation Issues

The PRBerm™ technology does not involve the use of any toxic or hazardous chemicals. The TRAPPS™ amendment is not regulated and is approved for addition to soils. The TTF also are not regulated.

The potential for off-range migration of munitions metals should be investigated prior to implementing any management strategy. If migration potential is present and threatens nearby open water or groundwater resources, then Clean Water Act and Safe Drinking Water Act regulations may be of concern to ongoing range operations.

The primary end user for this innovative in situ technology will be managers of active small arms ranges. The technology is expected to stabilize munitions metals within the impact berm before they can migrate to surface water or storm water discharge areas.

Technology transition efforts planned include presentation to range managers at the next TSS Workshop, publication in an American Society of Civil Engineers (ASCE) journal, and publication in trade journals for range managers. The completed, approved reports will also be forwarded to Defense Technical Information Center (DTIC).