Hazardous Waste Characterization

TTLC and STLC are used when determining the hazardous waste characterization under California State regulations as outlined in Title 22 of the California Code of Regulations (CCR). TCLP is the characterization based on federal guidelines. The intent of the leachate procedures is to simulate the conditions that may be present in a landfill where water may pass through the land filled waste and travel on into the groundwater carrying the soluble materials with it.

TTLC- Total Threshold Limit Concentration

This analysis determines the total concentration of each target analyte in a sample. Samples are analyzed by EPA 7420 for lead. When any target analyte exceeds the TTLC limits the waste is classified as hazardous and its waste code is determined by the compounds that failed TTLC. The results of this analysis can be used to determine if analysis for STLC level is necessary by comparing 10 times the STLC limit to TTLC results. A factor of ten is necessary to compensate for a 1:10 dilution factor that is present in one analysis but not the other. If the TTLC results do not exceed 10 times the STLC limit then normally no further analysis is required.

STLC- Soluble Threshold Limit Concentration

This analysis determines the amount of each analyte that is soluble in the "Waste Extraction Test", (WET) leachate. This WET leachate procedure is used for solid samples or for samples containing < 0.5% solids. The sample is tumbled in 10 times its weight of a 0.2M sodium citrate buffer for 48 hours. This leachate is then analyzed to determine the soluble concentrations.

TCLP- Toxicity Characteristic Leaching Procedure

This analysis, like the WET, determines the soluble portion of the analytes. This is a federal guideline and differs from the State in several ways. The alkalinity of the sample must first be determined in order to know which of two different extraction fluids should be used. Samples with a low alkalinity use extraction fluid #1 which is a sodium acetate solution with a pH of 4.93. Samples with a high alkalinity use extraction fluid #2 which is a dilute acetic acid solution with pH of 2.8. The sample is then tumbled in the appropriate extraction fluid for 18 hours

STLC / TCLP Extraction for Lead

Table I - List of Inorganic Substances and Applicable Regulatory Limits

Elements (Symbol)	TTLC	STLC	TCLP
	mg/Kg	mg/L	mg/L
Lead (Pb)	1,000	5.0	5.0