|Vanderbilt Univ., Nashville, TN. Dept. of Civil and Environmental Engineering.; North Carolina State Univ. at Raleigh. Dept. of Statistics.; Netherlands Energy Research Centre, Utrecht.; ARCADIS Geraghty and Miller, Inc., Research Triangle Park, NC.; Environmental Protection Agency, Washington, DC. Office of Solid Waste and Emergency Response.; National Risk Management Research Lab., Cincinnati, OH. Office of Research and Development.; Environmental Protection Agency, Research Triangle Park, NC. National Risk Management Research Lab.
The potential impact to the environment from disposal or other forms of land placement for a solid material has traditionally been determined from the results of one or more leaching tests. Currently, the Toxicity Characteristic Leaching Procedure (TCLP; EPA, 1992a) is the leaching test promulgated by the United States Environmental Protection Agency (EPA) for classification of wastes and for identification of materials considered Ã¢â‚¬Å“hazardousÃ¢â‚¬ï¿½ to the environment under the Resource Conservation and Recovery Act (RCRA). TCLP simulates leaching under a plausible worst-case mismanagement scenario of co-disposal of the test material with municipal solid waste. While a worst-case simulation test has merits for classification purposes, simulation-based leaching approaches inherently limit the usefulness of the test results to specific scenarios, waste materials, and disposal or use applications. A more flexible and robust leaching assessment methodology could provide EPA and the waste management community with a uniform basis for leaching characterization that is more broadly applicable to a wide range of waste types and release scenarios. To this end, the EPA Office of Solid Waste and Emergency Response (OSWER) has initiated further maturation of the leaching test methods contained within the Leaching Environmental Assessment Framework (LEAF) based on a tier-testing approach (Kosson et al., 2002). The LEAF methods are under consideration by OSWER for potential inclusion in EPAÃ¢â‚¬â„¢s compendium of laboratory methods, Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, also known as SW-846. Instead of simulating a particular release scenario, the LEAF methods challenge a solid material to a broad range of leaching conditions that may plausibly occur during the course of waste management and focus on a select set of key parameters considered to largely control the liquid-solid partitioning (LSP) and the mass transport of constituents from most solid materials. The LEAF approach (i.e., test methods, data management tools and leaching assessment methodologies) has been developed as a collaborative effort between Vanderbilt University (VU), the Energy Research Centre of the Netherlands (ECN) and DHI Denmark (DHI) with additional support and guidance from ARCADIS-US, Inc. (ARCADIS) and EPA Office of Research and Development (ORD) and the EPA Office of Solid Waste and Emergency Response (OSWER). LEAF provides considerable flexibility for environmental assessment in that no specific leaching scenario is imposed. The LEAF methods rather focus on intrinsic leaching characteristics and a range of conditions that affect leaching and vary in the disposal environment. Therefore, the results of LEAF testing may be applied to specific release conditions or used to compare multiple scenarios representing a range of plausible management options. As part of the review for SW-846, documentation is required regarding the precision (i.e., repeatability and reproducibility) of the methods for various types of potential waste materials. These precision data are intended to provide perspective on the variation in test method results that may be anticipated (i) when a single laboratory performs replicate testing of the method on the same homogeneous material sample (i.e., repeatability), or (ii) when multiple laboratories perform the method on replicate samples of a single material (i.e., reproducible). In addition, the precision data support the development of guidance on the use of the method and can be used to establish criteria for acceptable laboratory performance when using the method.