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TCLP stands for Toxicity Characteristic Leaching Procedure, the laboratory extraction in EPA SW-846 Method 1311. It is used to decide whether a waste exhibits the toxicity characteristic under US hazardous-waste regulation (40 CFR 261.24). The search term also returns Traverse City Light and Power, which is unrelated. “TLCP” is a common misspelling of the same acronym.
Reader task: a lab manager, environmental health and safety officer or waste coordinator who needs to know what a TCLP result means, what the method does, and which limits apply. This page explains the method; it is not a substitute for the regulation or your testing laboratory’s report.
Definition and scope
EPA describes Method 1311 as designed to determine the mobility of both organic and inorganic analytes present in liquid, solid and multiphasic wastes. It simulates leaching, not total content: the question is how much of a contaminant moves into an acidic extraction fluid, not how much is present in the material. EPA classes it as a method-defined parameter, so the result is only valid when the method is followed as written, and it may not be modified for RCRA testing.
The regulatory hook is 40 CFR 261.24: a solid waste exhibits the toxicity characteristic if, using Method 1311, the extract from a representative sample contains any listed contaminant at or above its regulatory value. Where the waste has under 0.5% filterable solids, the filtered waste itself is the extract. Waste identified this way carries a D-code; see RCRA hazardous waste codes and hazardous waste determination for where TCLP fits in the wider determination.
How does TCLP work?
The decision logic below is taken from the Method 1311 text (July 1992).
- Check the solids content. A waste with less than 0.5% dry solids is treated as a liquid (see the next section).
- Separate the phases. For waste at or above 0.5% solids, any liquid phase is separated from the solid phase.
- Reduce particle size if needed. The method calls for material to pass a 9.5 mm sieve.
- Extract the solid. The solid is extracted with a fluid weighing 20 times the weight of the solid. The fluid, which is acetic-acid based (extraction fluid #1 is pH 4.93 ± 0.05; fluid #2 is pH 2.88 ± 0.05), is selected according to the alkalinity of the solid.
- Tumble. The mixture is rotated end over end at 30 ± 2 rpm for 18 ± 2 hours at 23 ± 2 °C.
- Filter. The extract is filtered through a 0.6 to 0.8 µm glass-fiber filter.
- Combine and analyse. If compatible, the initial liquid phase is combined with the extract and analysed together; otherwise each is analysed separately and the results are combined mathematically as a volume-weighted average.
For volatile analytes the method uses a zero-headspace extraction vessel (ZHE) so that volatiles are not lost during extraction.
Early exits written into the method
- If the analytes of concern are absent or too low to exceed the regulatory levels, TCLP need not be run (section 1.2).
- If one liquid fraction already exceeds the level even after dilution, the waste is hazardous and the remaining fractions need not be analysed (section 1.3).
- A result from a bottle extractor that exceeds the volatile limit shows the waste is hazardous, but a bottle result cannot demonstrate that volatiles are below the limit; the ZHE is needed for that (section 1.4).
Can you TCLP a liquid?
Yes. Under Method 1311, a liquid waste (less than 0.5% dry solids) is filtered through a 0.6 to 0.8 µm glass-fiber filter, and the filtrate is itself the TCLP extract. There is no 20-to-1 extraction step for such a waste. 40 CFR 261.24 says the same: for waste with under 0.5% filterable solids, the filtered waste is the extract.
TCLP limits table (RCRA metals)
These are the eight metal values from Table 1 of 40 CFR 261.24 (read 2026-11-07, via Cornell LII). A TCLP extract at or above the value means the waste exhibits the toxicity characteristic for that contaminant. The same table also lists pesticides and organic compounds (D012 to D043), which are not reproduced here.
| D-code | Contaminant | Regulatory level (mg/L) |
|---|---|---|
| D004 | Arsenic | 5.0 |
| D005 | Barium | 100.0 |
| D006 | Cadmium | 1.0 |
| D007 | Chromium | 5.0 |
| D008 | Lead | 5.0 |
| D009 | Mercury | 0.2 |
| D010 | Selenium | 1.0 |
| D011 | Silver | 5.0 |
What is the TCLP threshold for lead?
5.0 mg/L (D008) in the TCLP extract, at or above which the waste exhibits the toxicity characteristic for lead under 40 CFR 261.24.
Where it matters for labs and waste decisions
A generator must determine whether its waste is hazardous. The characteristic can be established by testing or by process knowledge; TCLP is the test route for the toxicity characteristic. Because the method is defined by its procedure, a lab asked for “TCLP metals” is extracting by Method 1311 and then analysing for the listed metals. Once a waste is classed hazardous, shipment is tracked on a manifest; see the hazardous waste manifest guide.
Common misunderstandings
- TCLP is not a total-metals test. It measures what leaches into the extraction fluid under the method’s conditions, and the limits apply to the extract in mg/L.
- It is not only for solids. Liquids with under 0.5% solids are covered by the filtration shortcut.
- The method is not adjustable. As a method-defined parameter, changes to time, fluid or agitation produce a result that is not a Method 1311 result for RCRA purposes.
- A bottle result cannot clear volatiles. Only a ZHE extraction can show volatiles are below their limit.
FAQ
What does TLCP stand for?
TLCP is a misspelling of TCLP, the Toxicity Characteristic Leaching Procedure (EPA SW-846 Method 1311).
How does TCLP work?
It extracts a waste sample with an acetic-acid-based fluid (20 times the solid’s weight, 18 hours, 30 rpm, 23 °C), filters the extract and analyses it against the 40 CFR 261.24 limits. See the step list above.
What is the TCLP threshold for lead?
5.0 mg/L in the extract (D008).
Can you TCLP a liquid?
Yes; a liquid with under 0.5% dry solids is filtered and the filtrate is the extract.
Sources
- US EPA, SW-846 Test Method 1311: Toxicity Characteristic Leaching Procedure, July 1992 (PDF) and the EPA method page, read 2026-11-07.
- 40 CFR 261.24, Toxicity characteristic, Cornell LII, read 2026-11-07.
