California Department of Resources Recycling and Recovery (CalRecycle) 

LEA Advisory #56—November 4, 1998

Attachment 1—Characterizing Burn Dumps in California


Based on several burn dump investigations California Integrated Waste Management Board (IWMB) staff have determined that there may be elevated levels or hazardous levels of arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, and zinc in the soil/ash. Also, low levels of total recoverable petroleum hydrocarbons and/or low to nondetectable levels of semivolatile organic compounds, polychlorinated biphenyls (PCB), dioxins, and furans may be present in burn ash. The pH in the burn ash is expected to range from 6.0 to 9.0. When waste characterization of a burn dump is necessary an investigation must be performed to delineate the nature and extent of the waste and to determine if the burn ash is a Resource Conservation and Recovery Act (RCRA) hazardous waste, a non-RCRA hazardous waste (designated California hazardous waste), or a nonhazardous solid waste. Once the waste classification is established, the appropriate and effective remediation measures can be determined. To accomplish this objective the burn ash should be sampled and analyzed using one or more of the testing protocols describe below.

The IWMB’s Solid Waste Cleanup Program (SWCP) has developed a waste characterization methodology and actively evaluated burn dumps throughout California. The SWCP considers a variety of factors in assessing burn dumps and recommends the following procedures for the waste characterization. The components of the waste characterization include:

  1. Developing a sampling plan.
  2. Performing discrete sampling following a recommended sampling procedure.
  3. Analyzing samples using recommended analytical procedures and testing methodologies.
  4. Comparing sampling results with regulatory limits.

The use of SWCP's waste characterization methodology is only a recommendation. Depending on site conditions other city, county, State, or federal agencies may require additional sampling, analyses, and assessments.

Waste Characterization Methodology

Sampling Plan

A sampling plan is necessary to document the procedural and analytical requirements to collect soil samples to characterize areas of potential contamination from a burn dump. The intent of the plan is to provide the necessary documentation to characterize the burn dump ash. At a minimum the plan should discuss: site location and background, project purpose, project tasks, methodology, equipment, sampling procedures and locations, decontamination, sample containers and preservation, disposal of residual materials, analyses of concern, analytical procedures, quality control, chain of custody, and health and safety issues. The number of samples will vary depending on the size, location, and site conditions.

Sampling Methodology

The SWCP staff use authoritative discrete sampling to assess the burn ash and surrounding soils. Authoritative sampling is based on the subjective judgement of the investigator regarding the location of potential contamination and serves as a valuable investigative tool in ascertaining if a hazardous substance is or is not present.

Sampling Procedures

The SWCP uses appropriate sampling, collecting, decontamination, and storage techniques. All environmental samples are sent to a state-certified hazardous waste laboratory for analyses using chain-of-custody protocols.

Testing Protocols

In a waste characterization study burn ash samples are analyzed using one or more test protocols. Each test protocol produces its own specific type of information for a given range of conditions.

Four test protocols that are widely used are:

Protocol 1: Totals Test. The "totals test" is a chemical digestion test developed by the Department of Toxic Substances Control (DTSC) to determine the total amount of a specific constituent in the soil. A sample is digested chemically to obtain its soluble and insoluble fractions. The total of the soluble and insoluble fractions of the sample is then compared to the total threshold limit concentration (TTLC). The results of the Totals Test are reported in milligrams per kilogram of sample (mg/kg).

Protocol 2: Waste Extraction Test (WET). The WET is a leaching test developed by DTSC. Results of the WET are compared to the Soluble Threshold Limit Concentration (STLC). The WET determines the amount of a specific constituent that can be leached from the soil using a solution designed to simulate landfill leaching. It is therefore a useful test for situations where a soil would be exposed to landfill leachate, such as disposal of ash together with uncombusted organic wastes in a solid waste landfill. However, the WET may not be very representative of the conditions at a site where all organic material has been completely burned. Because of the aggressive nature of the leaching in this test samples may exceed the STLC. The results of the WET are reported in milligrams per liter (mg/l).

Protocol 3: Toxicity Characteristic Leaching Procedure (TCLP). The TCLP was developed by the federal Environmental Protection Agency (U.S. EPA) to determine if a waste is a RCRA waste subject to regulation under Subtitle C. The TCLP is a leaching procedure that uses a slightly less aggressive leaching agent than is used by the WET. The TCLP ensures that any volatile constituents present in the sample are collected and measured. However, few volatile constituents are likely to be found in completely combusted burn ash. Therefore, when compared to the WET results it is likely that TCLP results will indicate lower metals concentrations and less elevated levels of volatile constituents. Chromium is one of the few constituents that may be present in higher concentrations in TCLP results than in WET results. Chromium concentrations are higher because the TCLP results do not differentiate between the 3+ and 6+ chrome species, but report the two species combined. In contrast, the WET reports the 3+ and 6+ species separately. The results of the TCLP are reported in milligrams per liter (mg/l). Temperatures reached during open burning are usually not high enough to completely combust all waste materials in the burn ash. Therefore, in a worst case situation, incomplete combustion may create dioxins and other organic compounds.

Protocol 4: Deionized Water Waste Extraction Test (DI WET). The DI WET is used to characterize the amount of metals that would leach from ash under the conditions most likely to be encountered at burn dump sites. This test is essentially the same test as the WET, but uses deionized water as the leaching agent. At most burn dump sites the primary liquid that will come in contact with burn ash is water, not landfill leachate. Results of tests done on samples of burn ash from a variety of burn dump sites indicate that very few samples release any metals when tested under the DI WET protocol.

Analytical Procedures

Typically, all samples are analyzed for California Assessment Manual (CAM) 17 metals using the Totals Test procedure by EPA Method 6010/7000 and pH by EPA Method 9040. Samples (i.e., at least three) with the highest concentration of lead based on the Totals Test are also analyzed for CAM-5 metals using the WET procedure and RCRA Eight Metals using the TCLP. Also, if the WET results for any other metal not in the CAM-5 analysis exceeds 10 times the STLC regulatory level a separate WET analysis for that metal must be performed. In addition, the IWMB use the highest lead samples and analyze again for lead using the DI WET extraction procedure. Sampling for PCBs, total recoverable petroleum hydrocarbons (TRPH), and semi-volatile organic compounds may be necessary if visual observation or records indicate possible contamination.

At minimum the SWCP staff recommends all soil/ash samples be analyzed for:

  • CAM 17 Metals (Sb, As, Ba, Be, Ce, Cr, Co, Cu, Pb, Hg, Mo, Ni, Se, Ag, Tl, V, Zn) Totals Test, EPA Method 6010/7471
  • pH, EPA Method 9040

And the three samples containing the highest lead be analyzed for:

  • CAM 5 Metals (Cd, Cr, Ni, Pb, Zn), WET, EPA Method 6010
  • TCLP RCRA Metals (Ag, As, Ba, Cd, Cr, Hg, Pb, Se), EPA Method 1311

Additionally, the LEA may request the following sampling procedures:

  • PCBs, EPA Method 8080
  • Total Recoverable Petroleum Hydrocarbons (TRPH), EPA Method 418.1
  • Semi-Volatile Organic Compounds, EPA Method 8270
  • Lead DI-WET, WET, EPA Method 6010

In addition, testing for dioxins and furans may be appropriate if evidence suggests that these constituents would likely be present from the type of waste combusted, and/or the site is located in an urban area with a number of sensitive receptors nearby and where there is a higher risk to human health and safety.

Regulatory Limits

To characterize the ash, SWCP staff use regulatory limits established from the California Code of Regulations, Title 22, section 66261.10 et seq. and the Code of Federal Regulations, Title 40, Section 261.24. The sample results are compared to the TTLC and STLC, and the federal RCRA Standards. This comparison provides the basis for classifying the burn ash as either a RCRA hazardous waste, a non-RCRA hazardous waste (designated California hazardous waste), or a non-hazardous solid waste. Burn ash that contains concentrations of metals that exceed the TTLC or STLC limits, or established health based levels that the DTSC has determined to be protective of human health and the environment, may be considered hazardous waste as defined in Title 14, California Code of Regulations, section 17225.32. In addition, wastes that exceed the TCLP concentration limits would be considered a RCRA hazardous waste.

Examples of Burn Ash Analytical Test Results in California

Table 1 shows the highest concentrations from the totals test data of nine common metals found in ash sampled at 12 sites throughout California. These numbers represent the total amount of certain metals that are present in the soil. These results show that ash commonly contains lead in excess of the California standard for hazardous waste, with nickel and zinc also found at elevated levels. Some of the tested sites also showed elevated levels of arsenic and chromium.

Table 2 compares the results of testing of a single sample using the Totals Test, WET, TCLP, and DI WET test protocols. Samples tested under the Totals Test protocol that exceed the TTLC hazardous threshold for lead also will likely exceed the STLC hazardous threshold for lead. However, a sample tested under the TCLP protocol, with its less aggressive leaching agent, will probably not exceed the hazardous threshold concentration associated with the TCLP test. If the sample is tested under the DI WET protocol the sample again probably will not exceed the STLC hazardous threshold concentration limits.

Table 1
Summary of Highest Totals Test Values of Selected Metals at Burn Dump Sites within California Compared to TTLC Limits

Table 2
Comparison of Burn Dump Ash Test results

Advisory 56

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