PIMS:Remediation of Soil and Groundwater Contaminated With Metals

Abstract : Lead-contaminated soils are prevalent in the United States, particularly at Department of Defense (DoD) sites, which have more than 3,000 small arms firing ranges (SAFR). Private SAFRs and police practice SAFRs constitute an additional 9,000 sites. Estimates of lead-contaminated soil from range use in the United States are 100 million cubic yards, far exceeding that which can be disposed to landfills. These soils pose one of the costliest environmental issues facing the DoD, with costs estimated at more than $10 billion to dispose of them with existing baseline technologies, even if sufficient landfill space did exist. Additionally, large quantities of lead-contaminated leachates generated by rainfall and irrigation at many military sites flow into lakes or storm water drain systems, or provide contaminated recharge to shallow aquifers. The phosphate-induced metal stabilization (PIMS ) technology discussed in this report is an in situ stabilization or sequestration technology that uses a natural, benign material, Apatite II , which is mixed into the contaminated soil to immobilize lead (Pb) without changing the basic nature of the soil, e.g., the permeability, porosity, or density. This technology allows the soil to function in the future as a soil to be left in place, or disposed of as a nonhazardous material if desired. Apatite II is a natural phosphate material that incorporates metals into new stable phosphate phases that are nonleachable. Only simple mixing into the soil is required. The advantages over other technologies are that PIMS with Apatite II is inexpensive, fast, longlasting, and does not in itself generate any hazard or environmental problem.