Good summary on toxicology of Fly ashes and reasons for concern
Background
Disposal of coal combustion wastes presents potential environmental and public health concerns that justify imposition of rigorous design and monitoring standards. The 1988 U.S. Environmental Protection Agency Report to Congress concerning coal combustion wastes (including fly ash, bottom ash, boiler slag and flue gas emission control wastes) acknowledged the range of toxicity and potential for causing groundwater contamination among and within the categories of coal combustion waste. 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 (100 x drinking water standards) 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. Id.
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, a recent 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, which was based on extensive literature review and analysis of coals burned in Indiana utilities (including Kentucky coals), and which should instruct the imposition of final conditions on this permit, were:
l. Neither EP 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. l7 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.
5. Disposal of CCW in mine workings may be of particular concern, due to the increase in surface area available for leaching of elements resulting from fracturing of overburden and confining layers; and due also to the higher total dissolved solids levels in mine spoils that compete for sorption sites on solids with toxic elements released from the buried ash.
The EPA Report and Boulding study suggest that the management of special wastes at the proposed site must be attuned to the variability of the concentrations of potentially toxic elements in the waste, and to the unique problems presented by the previously-mined nature of the site, and by the fact that the type of special waste is from a fluidized bed combustor.
The 1988 EPA Report concluded preliminarily 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. This conclusion was recently reaffirmed by the agency on an interim basis. 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. This permit, consistent with the problems posed by this type of waste stream and disposal site identified by the literature, and consistent with EPA?s recommendations, should include rigorous controls on placement of the waste, strict limits on concentrations of contaminants in discharge water, and liners in all disposal cells and leachate storage or management ponds or lagoons.
Note: The above is borrowed from another organization working on similar issues in Kentucky...
Jim Puckett