Superfund Innovative Technology Evaluation (SITE)
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Rocky Mountain Remediation Services, L.L.C. (RMRS), of Golden, Colorado, has developed Envirobond™ to treat soil contaminated with metals. RMRS claims that Envirobond™ forms metal complexes that immobilize toxic metals, thereby reducing the risk to human health and the environment.
The Superfund Innovative Technology Evaluation (SITE) Program evaluated an in situ application of the technology during a demonstration at two lead contamination sites in Roseville, Ohio, in September 1998. For the demonstration, Envirobond™ was applied to 10 experimental units at a trailer park and one experimental unit at an inactive pottery factory.
Primary objective 1 (P1) was to evaluate whether Envirobond™ can treat soil contaminated with lead to meet the Resource Conservation and Recovery Act (RCRA)/Hazardous and Solid Waste Amendments (HSWA) alternative universal treatment standards (UTS) for land disposal of soils contaminated with lead. The alternative UTS for soil contaminated with lead is determined from the results of the toxicity characteristic leaching procedure (TCLP). The alternative UTS is met if the concentration of lead in the TCLP extract is no higher than one of the following: (1) 7.5 milligrams per liter (mg/L), or(2) 10 percent of the lead concentration in the TCLP extract from the untreated soil. Contaminated soils with TCLP lead concentrations below the alternative UTS meet the RCRA land disposal restrictions (LDR), and thus are eligible for disposal in a land-based RCRA hazardous waste disposal unit. The .alternative UTS is defined further under Title 40 of the Code of Federal Regulations (CFR), Chapter 1, part 268.49 (40 CFR 268.49). To meet that objective, soil samples were collected before and after the application of Envirobond™. The untreated and treated soil samples were analyzed for TCLP lead concentrations to evaluate whether the technology met objective P1. Analysis of the data demonstrated Envirobond™ reduced the mean TCLP lead concentration at the inactive pottery factory from 382 mg/L to 1.4 mg/L, a reduction of more than 99 percent. Therefore, the treated soil meets the alternative UTS for soil at the inactive pottery factory. Data from the trailer park were not used to evaluate P1 because TCLP lead concentrations in all treated and untreated soil samples from this location were either at or slightly higher than the detection limit of 0.05 mg/L.
Primary objective 2 (P2) was to evaluate whether Envirobond™ could decrease the soil lead bioaccessibility by 25 percent or more, as defined by the Solubility/Bioaccessibility Research Consortium's (SBRC) Simplified In Vitro Test Method for Determining Soil Lead and Arsenic Bioaccessibility (simplified in vitro method [SIVM]). However, EPA Lead Sites Workgroup (LSW) and Technical Review Workgroup for lead (TRW) at this time, do not endorse an in vitro test for determining soil lead bioaccessibility (Interstate Technology and Regulatory Cooperation [ITRC] 1997).To meet objective P2, soil samples were collected before and after the application of Envirobond™.The soil samples were analyzed for soil lead bioaccessibility to evaluate whether the technology met objective P2. Analysis of the data demonstrates that Envirobond™ reduced the soil lead bioaccessibility by approximately 12.1 percent, which is less than the project goal of at least a 25 percent reduction in soil lead bioaccessibility. However, it was recognized early on that meeting this goal would be difficult because the SIVM test procedure used in the demonstration involves a highly acidic sample digestion process, which may be revised in the future, because it may be exceeding the acid concentrations that would be expected in a human stomach.
An economic analysis examined 12 cost categories for a scenario in which the Envirobond™ process was applied at full scale to treat 807 cubic yards lead contaminated soil at a 1-acre site within the CRPAC. The cost was estimated to be $41.16 per cubic yard of treated soil. However, the cost for using this technology is site-specific.