Frequent Questions

We believe that the strength of the acid solution in Method 1311 should be increased in order to leach more of the contaminants from the sample. We also want to use it to test additional analytes. Are we allowed to do that?

The Toxicity Characteristic Leaching Procedure (TCLP), Method 1311, is a method-defined parameter, which means that the results depend entirely on how the test is conducted. 

The test was designed to model a theoretical scenario in which a waste is mismanaged by placing it in an unlined landfill containing municipal solid waste. The acetic acid solution in Method 1311 is designed to simulate the result of rainwater infiltrating the landfill, reacting with the municipal solid waste, and then leaching through the waste being tested. The numerical limits for the RCRA toxicity characteristic (40 CFR 261.24) were derived using the same scenario and were set at levels that would prevent the groundwater under the landfill from posing a threat to human health and the environment. 

As a result, the specific details of Method 1311 and the numerical limits for the toxicity characteristic itself are linked together. Increasing the acid strength of the leaching fluid to leach a larger amount of any of the constituents changes the scenario that the test was designed to simulate. Therefore, one would have to consider changing the numerical limits for the constituents listed in the toxicity characteristic too. Similarly, if one adds constituents to the list of those to be tested, one would have to develop numerical limits for them using the same sort of model that EPA used for the toxicity characteristic.
If you are interested in recent developments in leaching science, you may wish to review the proceedings of EPA's July 1999 meeting on leaching at:

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