2009-04-13_REVISION - M2008012 (17)

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The TCLP procedure continues to be the primary hazardous materials toxicity and treatment evaluation method utilized by the EPA. However, with the more recent development of the SPLP extraction procedure, and the methodology behind its development, the SPLP has become increasingly popular as a method of evaluating the potential leaching of hazardous constituents from site materials. The SPLP extraction procedure was initially brought about as a result of a lawsuit brought against the EPA by the Edison Electric Institute, the National Mining Association and several other petitioners to challenge the validity of the TC Rule and the TCLP procedure. The lawsuit stated that the mining industry disposed of their waste in their own on-site landfills and that mixing with municipal wastes did not occur. Therefore, organic acids would not contact the mining wastes and the TCLP would not apply. In connection with this lawsuit, the mining industry petitioned to use the SPLP method to evaluate the potential for leaching of metals from the on-site landfills. The SPLP method was designed by the mining industry to evaluate the potential for leaching metals into the indigenous and surrounding ground and surface waters. This extraction method provides a more realistic assessment of the metal mobility under actual field conditions and simulates the leaching efforts of acid rain / snow. This leaching fluid is intended to simulate precipitation. It is generally the chosen method when evaluating the fate and transport of metals in a properly engineered waste disposal facility when municipal solids are excluded. The SPLP extraction procedure is performed in a similar manner to the TCLP, with the exception of a different leaching fluid composition and method of leaching fluid selection. The SPLP procedure is performed by initially selecting one of two leaching fluids for the analysis. However, the method for selection of the appropriate leaching fluid does not depend on a hydrochloric acid buffering capacity test as in the TCLP procedure. Rather the SPLP leaching fluid is chosen based on the region of the country that the sample was obtained. Specifically, samples obtained fi•oni sites east of the Mississippi require the, use of Leaching Fluid #1 (LF 1), and sites west of the Mississippi require the use of Leaching Fluid #2 (LF 2). LF 1 is composed of deionized water adjusted to a pH value of 4.20:1-- 0.05 s.u. with a 60/40 mixture of sulfuric and nitric acids. LF 2 consists of deionized water adjusted to a pH value of 5.00 :L 0.05 s.u. with a 60/40 mixture of sulfuric and nitric acids. The pH values for each of the two leaching fluids are based on the average pH values for the eastern and western United States. The eastern United States typically experiences more acidic precipitation due to air pollution impacts from heavy industrialization and coal utilization. The precipitation in the western United States is typically less acidic since there is less industrialization and smaller population densities, thereby less automobiles. After leaching fluid selection, the sample is extracted in a rotary extractor over a period of 18 2 hours, at which time the extraction is terminated and the sample is filtered. After filtering the leachate is subjected to analyses in a similar manner as the TCLP. The current regulatory trend is an increase in the use of the SPLP leaching method due to more realistic conditions that the test represent. The EPA will mandate, not legislate the use of the SPLP extraction method in on-site disposal of metals waste that does not include municipal