2009-04-13_REVISION - M2008012 (17)

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INCIZEASllVG USE OF THE SPLP BY THE EPA Chemical characterization of a hazardous waste site focuses on two primary approaches. Total waste analyses evaluate the chemical makeup of site materials and are intended to identify the constituents of concern in site soils or sludges. Leachability analyses identify the potential for these constituents of concern to mobilize to the groundwater, thereby increasing their threat to human health and the environment. Until recently, the Environmental Protection Agency (EPA) has specified characterization of hazardous or waste materials through the Toxicity Characteristic Leaching Procedure (TCLP). In fact, the legal definition of a hazardous material is dependant upon the results of TCLP analyses. Recently, however, EPA has been initiating a gradual and unofficial change away from the use of the TCLP for characterizing a waste site. This change has led to the increased use of the Synthetic Precipitate Leaching Procedure (SPLP) for delineation and treatment verification testing. The TCLP, while legally providing the current definition of a hazardous material, was not the original leaching procedure identified by EPA. The original test developed by the EPA for determining whether a waste was hazardous by virtue of its toxicity was the Extraction Procedure Toxicity Test (EP Tox). This test was developed to simulate a worst-case scenario in which the potential hazardous waste would be co-disposed with municipal solid waste in a landfill with actively decomposing material. EPA reasoned that the most likely pathway for human exposure to toxic constituents would be through drinking water contaminated by landfill leachate. Based on the assumptions outlined above, EPA developed the EP Tox test relying on organic acids, simulating those commonly developed during anaerobic degradation occurring in municipal landfills. Through this procedure, materials were identified as being characteristically hazardous based on toxicity. This test was the primary leachability evaluation in use in the industry until 1986 when its successor, the TCLP was introduced. The TCLP extraction procedure was initially proposed by the EPA on 13 June 1986 with the introduction of the Toxicity Characteristics (TC) Rule. By 5 March 1990, the final rule and revision for the extraction procedure was signed by the EPA. The TCLP procedure was designed to simulate the leaching of chemicals by organic acids occurring in sanitary and/or municipal landfills. Therefore, acetic acid, an organic acid is used as the leaching fluid. The TCLP procedure which is found in 40 CFR 268 Appendix I and is identified as analytical method EPA SW-846 Method 1311, is performed through the use of two different leaching fluids. The procedure utilizes two different fluids to account for different buffering capacities in the materials tested. Specifically, Leaching Fluid 91 (LF 1) is deionized water adjusted to a pH value of 4.93 f 0.05 standard units (s.u.) with acetic acid and sodium hydroxide. Leaching Fluid #2 (LF 2) is deionized water adjusted to a pH value of 2.88 f 0.05 s.u. with acetic acid. The leaching fluid used for each sample is determined based on a hydrochloric acid buffering capacity test that is performed prior to the extraction.