Leaching Environmental Assessment Framework (LEAF) Methods and Guidance
The Leaching Environmental Assessment Framework (LEAF) is a leaching evaluation system, which consists of four leaching methods, data management tools, and scenario assessment approaches designed to work individually or to be integrated to provide a description of the release of inorganic constituents of potential concern (COPCs) for a wide range of solid materials. The LEAF Methods have been designed to consider the effect of key environmental conditions and waste properties on leaching. The LEAF How-To Guide describes how the LEAF method results can be used to develop screening level assessments of constituent release or to develop more accurate estimates of release in specific use or disposal scenarios.
- LEAF Methods
- Method 1313 - Liquid-Solid Partitioning as a Function of Extract pH Using a Parallel Batch Extraction Procedure
- Method 1314 - Liquid-Solid Partitioning as a Function of Liquid-Solid Ratio for Constituents in Solid Materials Using an Up-Flow Percolation Column Procedure
- Method 1315 - Mass Transfer Rates of Constituents in Monolithic or Compacted Granular Materials Using a Semi-Dynamic Tank Leaching Procedure
- Method 1316 - Liquid-Solid Partitioning as a Function of Liquid-Solid Ratio Using a Parallel Batch Extraction Procedure
- LEAF "How-To" Guide
- Frequent Questions about the LEAF Methods and "How-To" Guide
- LEAF Response to Public Comments
- Useful Resources
Method 1313 - Liquid-Solid Partitioning as a Function of Extract pH Using a Parallel Batch Extraction Procedure
Method 1313 is designed to evaluate the partitioning of constituents between liquid and solid phases at or near equilibrium conditions over a wide range of pH values. The method consists of 9-10 parallel batch extractions of solid material at various target pH values.
Method 1314 - Liquid-Solid Partitioning as a Function of Liquid-Solid Ratio for Constituents in Solid Materials Using an Up-Flow Percolation Column Procedure
Method 1314 is a percolation column test designed to evaluate constituent releases from solid materials as a function of cumulative liquid-to-solid ratio. The method consists of a column packed with granular material with moderate compaction. Eluent is pumped up through the column to minimize air entrainment and preferential flow.
Method 1315 - Mass Transfer Rates of Constituents in Monolithic or Compacted Granular Materials Using a Semi-Dynamic Tank Leaching Procedure
Method 1315 is a semi-dynamic tank leaching procedure used to determine the rate of mass transport from either monolithic materials (e.g., concrete materials, bricks, tiles) or compacted granular materials (e.g., soils, sediments, fly ash) as a function of time using deionized water as the leaching solution. The method consists of leaching a sample in a bath with periodic renewal of the leaching solution at specified cumulative leaching times.
Method 1316 - Liquid-Solid Partitioning as a Function of Liquid-Solid Ratio Using a Parallel Batch Extraction Procedure
Method 1316 is an equilibrium-based leaching test intended to provide eluate solutions over a range of liquid-to-solid ratios. This method consists of five parallel batch extractions of a particle-size-reduced solid material in reagent water over a range of liquid-to-solid ratios. At the end of the contact interval, the liquid and solid phases are separated for constituent analysis.
The purpose of the LEAF "How-To" Guide is to provide an understanding of the Leaching Environmental Assessment Framework to facilitate its broader use in environmental assessment. The guide provides background on the LEAF methods, guidance on how to perform the methods, and guidance on how to understand the method results. It also provides guidance on the application of LEAF to assess leaching potential of COPCs from solid waste materials for beneficial use, disposal, treatment, and remediation applications. In addition, the guide addresses frequently-asked questions about the four LEAF methods, data management and reporting using freely-available software, and potential applications of the LEAF approach.
LEAF may be useful in estimating the environmental impacts from utilization of secondary materials, primarily as construction materials. Leaching data from LEAF or other relevant leaching tests can be used in EPA’s Methodology for Evaluating Beneficial Uses of Industrial Non-Hazardous Secondary Materials, which presents a voluntary approach for evaluating potential adverse impacts to human health and the environment from a wide range of industrial non-hazardous secondary materials and their associated beneficial uses. Prior to beneficially using secondary materials in any projects, interested individuals or organizations should consult with the relevant state and federal environmental agencies to ensure proposed uses are consistent with state and federal requirements.
LEAF may also find application in support of cleanup decisions under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) that address specific contaminants on a site-specific basis. The performance values against which LEAF would be evaluated may differ depending on the specific regulatory program involved. For example, site-specific data is used to determine whether action is warranted at a site. Furthermore, under CERCLA as stated in the National Oil and Hazardous Substances Pollution Contingency Plan, “levels generally should be attained throughout the contaminated plume, or at and beyond the waste management area when waste is left in place” (55 FR 8753, March 8, 1990). Decision-makers should consult with the appropriate regulatory agency to ensure compliance when using LEAF testing in support of an evaluation.
Under CERCLA, cleanup decisions depend on site-specific factors. General guidance on use of LEAF data that would be applicable to all sites is impractical and beyond the scope of the How-to Guide. As such, EPA expects to provide additional guidance on the use of LEAF for CERCLA response actions as experience with LEAF evolves.
EPA has developed answers to frequently asked questions about the LEAF Methods and "How-To" Guide.
The public comment period for the LEAF methods and "How-To" Guide closed on January 31, 2018. Although submissions will no longer be accepted, the EPA Docket can be viewed by searching for ID# EPA-HQ-OLEM-2017-0210. EPA reviewed all comments and published a Response to Comments document along with the final versions of the methods and “How-To” Guide.
- LeachXS and LeachXS Lite
- LeachXS Lite data templates
- ORCHESTRA: geochemical speciation and reactive transport code
- PHREEQC: computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations
- MINTEQA2: geochemical equilibrium speciation model
- The Geochemist’s Workbench: geochemical modeling software
- IWEM: deterministic groundwater fate and transport model
- EPA’s Composite Model for Leachate Migration with Transformation Products (EPACMTP)
- EPA’s Leaching Test Relationships, Laboratory-to-Field Comparisons and Recommendations for Leaching Evaluation using the Leaching Environmental Assessment Framework (EPA/600/R-14/061)
- EPA’s Background Information for the Leaching Environmental Assessment Framework (LEAF) Test Methods (EPA/600/R-10/170)
- EPA’s Interlaboratory Validation of the Leaching Environmental Assessment Framework (LEAF) Method 1313 and Method 1316 (EPA/600/R/12/623)
- EPA’s Interlaboratory Validation of the Leaching Environmental Assessment Framework (LEAF) Method 1314 and Method 1315 (EPA 600/R-12/624)
- EPA’s Characterization of Mercury-Enriched Coal Combustion Residues from Electric Utilities Using Enhanced Sorbents for Mercury Control (EPA/600/R-06/008)
- EPA’s Characterization of Coal Combustion Residues from Electric Utilities Using Wet Scrubbers for Multi-Pollutant Control (EPA/600/R-08/077)
- EPA’s Characterization of Coal Combustion Residues from Electric Utilities—Leaching and Characterization Data (EPA/600/R-09/151)
- EPA’s Leaching Behavior of “AGREMAX” Collected from a Coal-Fired Power Plant in Puerto Rico (EPA/600/R-12/724)
- EPA’s The Impact of Coal Combustion Fly Ash Used as a Supplemental Cementitious Material on the Leaching Constituents from Cements and Concretes (EPA/600/R-12/704)
- EPA’s Final Report for Sampling and Analysis Project—Beneficial Use of Red and Brown Mud and Phosphogypsum as Alternative Construction Materials