The key to understanding the Toxicity Characteristic Leaching Procedure (TCLP) is being aware of which leaching solution is being used.

Although most people only look at the final results of the TCLP (EPA SW846 Method 1311), there are several important things to know about the actual test procedure.

  • There is a preliminary evaluation in the TCLP that is used to establish the intial pH of the waste which determines whether to continue with Solution 1 (a dilute acid with a pH of 4.93) of Solution 2 (a strong acid with a pH of 2.88).
  • If the initial pH of the waste is less than 5, then Solution 1 is used.
  • If the pH of the waste is above 5 at the end of the pre-test then Solution 2 is used.  Since it is a stronger acid, higher concentrations of metals will leach out using Solution 2.

Occasionally, EnviroBlend clients notice inconsistent TCLP results and contact an EnviroBlend representative.  After looking into it further, the laboratory typically finds that they were not consistently utilizing the correct TCLP preliminary procedure.  This, of course, can lead to disposing of non-hazardous waste as hazardous or hazardous waste as non-hazardous.  Both situations are risky and expensive.

It is important to make sure laboratories are running the pre-test for each sample.

To learn more about this topic contact:

  • EnviroBlend at 800-227-4287 or
  • Visit the U.S. Environmental Protection Agency website to read the full SW-846 Test Method 1311: Toxicity Characteristic Leaching Procedure

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