At Novesis, we are frequently asked about the differences between the TCLP and the SPLP tests, and the proper application for each method. To answer these questions we prepared a brief summary and overview below.
Please contact the professionals at Novesis (803-359-3123) with any questions you may have about TCLP and/or SPLP, we have considerable experience with both and their proper application(s).
TCLP vs SPLP
What are the differences between the Toxicity Characteristic Leaching Procedure (TCLP) (EPA SW-846 Method 1311) and the Synthetic Precipitation Leaching Procedure (SPLP) (EPA SW-846 Method 1312) extraction tests, with respect to environmental sampling and testing – and what is the appropriate circumstance to select one test over the other?
Both tests simulate, and then analyze, “leachate” which is defined as — any liquid that, in passing through matter, extracts solutes, suspended solids or any other component of the material through which it has passed. Both tests utilize similar sample processes and extraction processes.
The primary difference between the two test methods is the use of different extraction fluids, which are dictated by what each test was designed to simulate.
The TCLP was designed to simulate material sitting inside a landfill for a number of years (with an assumption of the acidic conditions found in most landfills), and then “determine the mobility of both organic and inorganic analytes present in liquid, solid and multiphasic wastes” from the leachate that material would produce. The Toxicity Characteristic Leaching Procedure is the only leaching procedure specified by regulation for characterizing the hazardous waste Toxicity Characteristic (40 CFR 261.24 – waste codes D004-D043) under the Resource Conservation and Recovery Act (RCRA) regulations. In other words, when attempting to make a hazardous waste determination for the Toxicity Characteristic (TC), TCLP is the only appropriate analytical method to run.
The SPLP was designed to simulate material sitting in-situ (in or on top of the ground surface) exposed to rainfall (with an assumption that the rainfall is slightly acidic) then “determine the mobility of both organic and inorganic analytes present in liquids, soils, and wastes” from the leachate the material would produce. Because the Synthetic Precipitation Leaching Procedure simulates actual environmental precipitation, and the leaching potential of a contaminant in soil, it offers a straightforward method to assess chemical mobility in the environment.
For determination of the Toxicity Characteristic (TC) per RCRA, the TCLP (Method 1311) is the only appropriate test. 40 CFR 261.24 (b) Table 1 contains a chart of constituents and the regulatory thresholds one would utilize to compare against TCLP analytical results, to make a hazardous waste TC determination.
For assessing the potential a contaminated material (left in situ) has to impact groundwater (or surface water), when exposed to normal weathering, the SPLP (Method 1312) is the appropriate test. SPLP results are utilized to develop site-specific soil remediation criteria that will be protective of groundwater. Federal or State guidance can be utilized to incorporate SPLP data into a Conceptual Site Model as part of a comprehensive environmental investigation and guide for determining the necessity of remediation or additional study.