Additional Testing Recommended For Coal Combustion Ash Used For Fill

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Additional Testing Recommended For Coal Combustion Ash Used For Fill  

Posted: July 1, 2007 

June 24, 2007

To: Ms. Sharon Dodson, e.on U.S.
George Siemens, e.on U.S.

From: Tom FitzGerald, Director

Re: Beneficial Use of Coal Combustion Wastes

As I had promised, I am writing to follow-up concerning the utilization of fly ash, bottom ash and combined fly and bottom ashes from various coal-fired power plants in the e.on U.S. LG&E and KU system as fill material for a sand mine, backfill material for utility trenches and as base material for public parks and warehouses.

According to the e.on U.S. 2006 Environmental and Community Investment Report, coal ash is being sent to Flynn Brothers Contracting as backfill for a noncoal sand mine; for building baseball fields in Woodford County, for development of a commercial business site in Lawrenceburg and for a warehouse in Jefferson County, and as foundation material for a bridge over Dixie Highway. Additionally, it is my understanding that backfill material that has been utilized for Metropolitan Sewer District utility trench construction was acquired from Charah Environmental and originated in your Mill Creek plant.

I have previously indicated my concern with the potential for leaching of constituents of concern from coal combustion wastes where the wastes are managed under field conditions that do not provide for isolation of the material from water infiltration nor isolate the resulting leachate from surface and groundwaters.

As I mentioned in our discussion, KRC is concerned that where these materials are used as fill (particularly in hydrogeologic settings where permeability is high such as sand and gravel pits) the short-term batch leaching tests utilized for testing of the leaching characteristics of the waste are not reflective of leaching under actual field conditions.

There is good reason to insist that prior to releasing coal combustion wastes for use as fill material, e.on U.S. assure that appropriate characterization is conducted of the short- and long-term leaching potential, both from a civic and a liability standpoint. These wastes contain a number of constituents of potential environmental and public health concern.

According to the EPA Report Wastes from the Combustion of Coal by Electric Utility Power Plants, EPA/530-SW-88-002:

The primary concern regarding the disposal of wastes from coal-fired power plants is the potential for waste leachate to cause ground-water contamination. Although most of the materials found in these wastes do not cause much concern (for example, over 95 percent of ash is composed of oxides of silicon, aluminum, iron and calcium), small quantities of other constituents that could potentially damage human health and the environment may also be present.

These constituents include arsenic, barium, cadmium, chromium, lead, mercury and selenium. At certain concentrations these elements have toxic effects.

Id., at ES-4.

While the findings of the EPA Report and review of industry-generated studies indicated generally that metals did not leach out of coal combustion waste (CCW) at hazardous levels, hazardous levels of cadmium and arsenic were found in ash and sludge samples, and boiler cleaning wastes sometimes contained hazardous levels of chromium and lead.


While acknowledging that coal combustion wastes (fly ash and scrubber sludge) do not usually exhibit sufficiently high toxic properties to be classified as "hazardous" based on TCLP toxicity (meaning they don't leach metals at 100x safe drinking water levels), a study of CCW in Indiana indicated that CCW does contain high enough concentrations of leachable toxic elements to create significant environmental concern. Boulding, J. Russell, Disposal of Coal Combustion Waste in Indiana: An Analysis of Technical and Regulatory Issues (1991).

Among the significant findings of this report, based on extensive literature review and analysis of coals burned in Indiana utilities (including Kentucky coals), are that:

1. Neither EP [toxicity] nor TCLP tests provide a good indication of leachability of CCW in natural disposal settings. Long-term leaching tests conducted until equilibrium has been achieved for each element of concern, using a leaching solution that approximated percolating groundwater, would give a more accurate depiction of ground-water contamination potential at a disposal site.

2. 17 potentially toxic elements are commonly present in CCW: aluminum, antimony, arsenic, barium, beryllium, boron, cadmium, chromium, copper, lead, manganese, mercury, molybdenum, nickel, selenium, vanadium, and zinc.

3. Fluidized bed combustion (FBC) wastes retain volatile and semi-volatile elements in the bottom ash to a greater extent than conventional pulverized coal combustion, thus enhancing the leachability of FBC waste elements.

4. Leachates from coal power plant ash and flue gas desulfurization wastes typically exceed drinking water standards, but by a factor less than hazardous levels (i.e. 100 x DWS). The major leaching studies on CCW indicate that drinking water standards are typically exceeded by CCW ash leachate at a factor of 1.1 to 10, and often by a factor greater than 10 for one or more elements.

The EPA Report and Boulding study indicate that the management of CCW must be attuned to the variability of the concentrations of potentially toxic elements in the waste, and to the different problems presented by disposal sites, and by the type of special waste (i.e. FBC v. non-FBC wastes).

While the EPA Report concluded that CCW need not be regulated under RCRA Subpart C as hazardous, but rather that the wastes should continue to be regulated under Subpart D as solid wastes. In so recommending, EPA determined that while field observations detected off-site migration of potentially hazardous constituents from utility waste disposal sites, reflecting a potentially larger problem than laboratory analyses would suggest, the use of mitigative measures under Subpart D such as installation of liners, leachate collection systems, and ground-water monitoring systems and corrective action to clean up ground-water contamination, would be adequate for protecting public health and the environment. The EPA recommendation was predicated on the application of such measures to the management of CCW. Id. at ES 4-5.

Unfortunately, such measures are not employed in these situations where the ash is given to another entity for "beneficial reuse" and is disposed of in unlined trenches and fill locations such as sand pits and ball fields.

Prior to land application of the waste ash, any potential for leaching or other environmental release (including dermal or airway exposure to metals sorbed to the ash) must be thoroughly considered and the material must be determined appropriate for the intended use both in the short and the long-term. The testing that I have seen to date appears to have been based solely on TCLP testing and analysis of ?total metals” through a test method not identified on the Table 3 Comparison of TCLP and Total Metals Analytical Results.

The only other testing of which I’m aware was conducted for Charah Environmental Inc. on Mill Creek power plant ash by the University of Kentucky, and reported only total metals, again without identifying the test method. Analysis of total metals does not provide any indication of the leaching potential or leaching characteristics of coal combustion wastes, and the U.S. EPA has recommended that management decisions not be based on total content of constituents in coal combustion residues since total content does not consistently relate to quantity released.

The literature summarized below reflects clearly that TCLP testing is insufficient to predict short-and long-term leaching characteristics of coal combustion fly and bottom ash as fill. Because of the limitations of TCLP testing, I am concerned that the resulting data is insufficient to demonstrate that, under the disposal/use conditions that are currently being allowed by e.on U.S., the environmental performance standards of 401 KAR Chapter 45 are being met.

The use of short-term batch leaching tests, such as TCLP, EP-Toxicity, SPLP, and ASTM-D2987 (Shake Extraction) are not necessarily reflective of field conditions and long-term leaching potential. According to Ann Kim of the National Energy Technology Laboratory, “[t]he utilization of coal combustion by-products (CCB) as bulk fill and mine backfill has raised questions about the potential contamination of surface and groundwater. . . . Leaching is related to the solubility of a specific compound and can be influenced by pH, temperature, complexation, and oxidation / reduction potential. . . . Regulatory tests and standard methods are not necessarily appropriate for leaching tests intended to stimulate natural processes.”

Kim, CCB Leaching Summary: Survey of Methods and Results.”

The TCLP test method is a batch test developed by EPA in response to deficiencies in an earlier test, the Extraction Procedure (EP). The test:

was designed as a screening test to consider conditions that may be present in a municipal solid waste (MSW) landfill. It is acetic acid buffered to pH 5 (initial); 20: 1 liquid/solid ratio; particle size reduction to 9.5 mm; equilibrium. The reason it was designed this way was because, under RCRA, EPA is required to regulate as hazardous all wastes that may pose a hazard to human health and the environment if they are mismanaged. . . . co-disposal of industrial solid waste with MSW is considered to be a plausible “worst-case” management of unregulated waste.

Helms, US EPA Leach Testing of Coal Combustion Residues.

As Gregory Helms with the EPA Office of Solid Waste explained, the EPA Science Advisory Board commented on the TCLP test method in 1991 and again in 1999, expressing concern “about overbroad use of the TCLP test.” Id. The SAB found that TCLP is a screening test that evaluates leaching potential under a single set of environmental conditions. The SAB has expressed concern over the use of the TCLP when it has been applied to determine the leaching potential of wastes in disposal settings other than municipal waste co-disposal.

The U.S. EPA utilized a new multi-tiered testing framework in a research program designed to evaluate the potential for mercury release from various types of coal combustion wastes. The alternative framework evaluates the potential leaching of waste constituents over a range of values for parameters that affect the leaching potential. In explaining the EPA decision to utilize a leach testing approach developed by Kosson et al. at Vanderbilt in evaluating leaching from coal combustion residues resulting from mercury emissions controls, Helms explained that TCLP wasn’t used for evaluating coal combustion residues from enhanced mercury controls because “TCLP is not technically appropriate” where the disposal is not co-disposal with MSW.

Other commentators have noted the limitations of the use of TCLP as an analytical method for predicting leaching potential of coal combustion wastes. Hassett notes that

The TCLP is often used in a generic manner for the prediction of leaching trends of wastes, although the intent of this test was for the prediction of leaching under co-disposal conditions in sanitary landfills. The application of acidic conditions to predict field leaching that can occur under a wide range of conditions may lead to false prediction of leaching trends. Additionally, conditions imposed on leaching systems by inappropriate leaching solutions may alter the distribution of redox species that would be found in the field and, in some cases with reactive wastes, 18 hours, as specified in the TCLP and other short-term leaching tests, may be an insufficient equilibration time. In order for a batch leaching test to be used, in determining potential for environmental impact . . . when being used with CCBs, the test must take into account the unique properties of the material, especially the hydration reactions of alkaline CCBs.

Hassett and Pflughoeft-Hassett, Evaluating Coal Combustion By-Products (CCBs) For Environmental Performance.

Because the tests are not designed for use with CCBs, they do not account for several typical reactions in CCBs under hydration. It has long been known that laboratory leaching procedures cannot precisely simulate field conditions nor predict field leachate concentrations. However, with careful application of scientifically valid laboratory procedures, it is possible to improve laboratory-field correlations and modeling efforts focused on predicting leachate concentrations. Id.

Hassett recommends the development of a selection of laboratory leaching procedures that more closely simulate field management scenarios, focusing specifically on technical and scientific variables such as the long-term hydration reactions that can impact leachate concentrations of several constituents of interest, the means by which water contacts the CCB in order to simulate the reduced permeability frequently exhibited in CCB utilization applications, the impact of pH and other CCB properties on the leachate and on resulting leaching; and the prediction of, and changes in, leaching over time. Id. Hassett recommends use of Synthetic Groundwater Leaching Procedure with a long-term leaching (LTL) procedure as a better predictor of leaching under field conditions. His work reflects that “[I]n many applications, the extended-time SGLP “has demonstrated trends significantly different from TCLP and other commonly used leaching protocols.”

The explanation for the differing results and trends between the extended-time SGLP and TCLP “can be explained by the fact that many commonly used leaching tests impose conditions different from those in a field environment on samples, and, thus, bias data in a manner leading to inappropriate interpretation for environmental impact. Elements most often affected include arsenic, boron, chromium, vanadium, and selenium.” Id.

The EPA Report on Characterization of Mercury-Enriched Coal Combustion residues from Electric Utilities Using Enhanced Sorbents for Mercury Control, EPA/600/R-06/008 (January 2006) further underscores both the importance of utilizing proper test methods for characterization of these coal combustion wastes, and the trend towards increasing potential toxicity of such wastes as air pollution controls better capture metals entrained in and released during combustion of the coal. Among the observations of the agency were that “arsenic and selenium may be leached at levels of potential concern from CCRs generated at some facilities both with and without enhanced mercury control technology [and that] further evaluation of leaching or arsenic and selenium from CCRs that considers site specific conditions is warranted.”

With respect to the sufficiency of TCLP, EPA noted that leaching tests “focused on a single extraction condition” would not have allowed for an evaluation of the variations in anticipated leaching behavior under the anticipated field disposal conditions.

401 KAR 45:060 grants a special waste permit-by-rule for “beneficial reuse of coal combustion by-products” as substitute product ingredients, as antiskid material, highway base course, and “structural fill” provided that the utilization complies with the environmental performance standards of 401 KAR 30:031, does not result in a nuisance condition, erosion and sediment control measures are used, certain distances from streams, wells, floodplains and wetlands are maintained, an annual report is provided to the state, and “the generator characterizes the nonhazardous nature of the coal combustion by-products[.]” 401 KAR 45:060 Section 1.

Assuming, for the sake of argument, that “structural fill” includes baseball fields and utility trench backfilling, the reliance on total and TCLP data rather than on laboratory data that more accurately and adequately characterizes the leaching potential and “nonhazardous” nature of the wastes over the long-term, appears to place e.on U.S. in a position where it cannot demonstrate with any degree of confidence that the use of these CCBs meets the characterization and management requirements of the “special waste permit-by-rule.” The coal combustion wastes may prove to leach constituents of concern at below levels of both regulatory and environmental concern, but the reliance on TCLP and total metals test methods is insufficient to support such a finding for these end uses.

I would strongly encourage your company to contract with an independent entity that is familiar with the specific issues relating to testing of CCBs in order to identify and then conduct appropriate longer-term leaching procedures, such as Kosson protocol, the LTL extended-time variant of the SGLP as described by Hassert and sequential leaching tests such as that described by Ziemkiewicz that leach the CCB with a sample of the water that will come into contact with the CCB (through surface infiltration of rainfall or groundwater) until the alkalinity is exhausted and the pH of the leachate returns to that of the encountered water. Such dynamic testing under a range of conditions will better predict the long-term leaching potential of these coal combustion wastes when used as fill in conditions where they are not isolated from surface or groundwater infiltration. I would also strongly recommend that further release of this material to third-party contractors or to public agencies for use as fill be suspended pending the conducting of appropriate tests better designed to replicate leaching characteristics of hydrated coal combustion ashes under field conditions.

Additionally, I would suggest that e.on U.S. engage in a dialogue with the Louisville Water Company and the Metropolitan Sewer District concerning the location and extent of any past use of coal combustion residues for sewer trench backfill within the Wellhead Protection Area in which the water company is planning to construct riverbank infiltration wells.

Finally, I would recommend that your company review the procedures under which these materials are being utilized. In correspondence with MSD in 2004, I asked whether landowners were informed that coal ash was being utilized to backfill sewer lines rather than the soil that had been removed or sand, and was informed that “[t]here were no notices provided to landowners concerning the use of coal ash as backfill. In most instances it was used in the right-of-way, however there may be instances where ash has been substituted for sand on private property.” June 15, 2004 Letter from Carolyn Shain, Legal Counsel, MSD. Irrespective of any contractual arrangements that you might have with third parties for the management and disposition of the coal combustion wastes for “beneficial reuse,” I believe your counsel would concur that there is potential residual liability as generator of these coal combustion wastes, particularly when your company is aware of the end use, and aware that the test methods employed may not accurately reflect the capability of those materials to meet the governing environmental performance standards of under field conditions. The lack of notice to and consent of landowners before using these materials instead of sand is of concern.

Thanks in advance for your consideration of these concerns.

Tom FitzGerald

cc: Greg Heitzman, LWC
Bud Schardein, MSD
Ron Gruzesky, DWM

By Kentucky Resources Council on 06/01/2018 5:32 PM
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