CCR: Understanding LEAF Methods and US EPA Guidance
The US EPA’s guidance document describing the application of the Leaching Environmental Assessment Framework (LEAF) has now been in place for 9 months. This framework consists of four US EPA leaching methods codified in SW-846 as Methods 1313 through 1316. The LEAF tests are designed to measure fundamental leaching behavior of solid substrates with provisions in the methods for monolith materials and have been applied to Coal Combustion Residuals (CCR) requirements. They are significant in that the US EPA methods do not determine a pass/fail as is used in toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP). Instead, the LEAF leaching endpoints include available content, maximum release, solubility, and leachate pH that can be extrapolated to site conditions for conceptual site model development.
Details on how to prepare and interpret the results are provided in the Guidance, but require significant planning steps and technical expertise in chemistry and geosciences to implement. Though other fundamental leaching tests are available (e.g., from ASTM), the LEAF methods provide a larger range of testing conditions (pH, liquid-to-solid ratios), yet the cost for performing a full suite of LEAF tests is significant. Environmental Standards, Inc. has been involved with quality assurance review and implementation of leaching methods, including those codified under the LEAF Guidance. Environmental Standards has prepared a White Paper on this Guidance for clients that describes how to interpret LEAF results, includes example costs, and how to best incorporate critical planning and ongoing assessment in a program that includes using these methods. There are important best-practices that we have learned when using leaching methods, especially the LEAF approach, as they are not used for pass/fail decision making.