TCLP or SPLP: Project Applicability

TCLP or SPLP?  EPA 1311 or EPA 1312?  When selecting the appropriate leaching procedure, it basically boils down to one key question.  What type of environmental project is the leaching procedure supporting?

The Toxicity Characteristic Leaching Procedure (TCLP) is performed as a waste characterization method to support waste disposal efforts for RCRA-listed compounds and elements. The SW-846 method for the TCLP extraction is EPA 1311. The TCLP method was developed as a scientific tool for evaluating the leaching potential of analytes for determining hazardous waste classification. The method states that TCLP is designed to determine the mobility of both organic and inorganic analytes present in liquid, solid, and multi-phasic wastes.  

Prior to starting the TCLP method, the laboratory must classify the waste sample received as a liquid waste or solid waste by determining percent solids.  If the sample is greater than 0.5% solid, the sample is characterized as a solid waste while a sample with less than 0.5% is characterized as a liquid waste.  Samples characterized as liquid waste become the sample extract and are prepped for analytical testing of the requested RCRA analytes.  

Solid waste samples are combined with an acetic acid buffer solution and tumbled as part of the TCLP extraction method.  After tumbling, the leachate from the extraction method is collected from the TCLP vessels and analyzed for the requested analytes. When TCLP volatile organics are requested, the TCLP Zero Headspace Extraction (ZHE) is performed.  Because of the volatile nature of VOCs, the ZHE procedure is used to prevent VOC loss during TCLP tumbling.  All other TCLP analyses are performed using the Non-ZHE tumbling procedure. After analytical testing is completed, the results should be compared to the TCLP regulatory limits to determine hazardous waste classification.

The Synthetic Precipitation Leaching Procedure (SPLP) method is very similar to TCLP, but its project applicability differs significantly.  SPLP is generally specific to soil samples and is performed to determine the potential of contaminants present in soil to leach into groundwater.  SPLP is often requested for projects where environmental engineers are concerned with evaluating the risk of potential groundwater contamination from the land application of waste materials to soil. TCLP is used for waste characterization for disposal at a landfill and can be performed on liquid, solid, or multi-phasic samples.  

The SPLP extraction procedure is performed by SW-846 method EPA 1312.  When volatile organics are requested for SPLP, the ZHE procedure is used similar to the procedure for TCLP volatile organics. The main difference between EPA 1311 (TCLP) and EPA 1312 (SPLP) is the buffer solution added to the samples prior to tumbling.  TCLP uses acetic acid while SPLP uses nitric acid and sulfuric acid. 

Merit Laboratories is one the leading environmental laboratories for supporting TCLP and SPLP projects with significant experience supporting a diverse range of waste sample types and contaminated soil characteristics.  Please contact Merit to discuss your project type to determine the applicable leaching procedure.