EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00344) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 23 XIII  23 EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00345)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00346)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00348)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00349)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00350)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00351)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00352)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00353)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00354)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00355)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00356)

EPA should make a strong effort to gather its own information on CCW contamination rather than relying on highly biased information supplied by industry. ( CITZ00357)

Your agency has been studying the disposal problem for many years and decision time is at hand. The industry has used every method they could muster to minimize the hazardous and toxic nature of these wastes and get the agency to treat them as benign substances. More competent studies are now available to you and we hope you will give them the attention they deserve. ( DCCC00359) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 24 XIII  24 EPA should ensure the objectivity, accuracy, and completeness of this report by: gathering its own information rather than relying on highly biased information supplied by the industry and state agencies which behave more as advocates than observers. ( POW00369)

I hope the EPA will strive to gather its own information on CCW contamination, rather than relying on coal company information. ( CITZL0013)

I think relying on the strip mining industry to police itself is like letting the fox into the henhouse. ( CITZL0015).

EPA properly relied on voluntarily submitted industry data in lieu of issuance of compulsory information demands. EDF sounds an alarm over EPA's reliance upon industry data and " failure" to invoke its authority under RCRA § 3007 to demand information from the industry. EDF's alarm is misplaced and fails to appreciate the statutory instruction for the Bevill study to proceed in a cooperative and efficient manner. Section 8002( n) of RCRA states that " the Administrator shall . . . invite participation by other concerned parties, including industry and other Federal and State agencies, with a view toward avoiding duplication of effort." 64 In response to EPA's invitation to participate, USWAG and EPRI provided EPA with a wealth of data that were collected and analyzed in close cooperation with the Agency over a period of 18 years. Industry's cooperation rendered it unnecessary for EPA to resort to its compulsory process authority. Whether or not such demands were necessary in other Bevill studies is irrelevant. EPA has been provided with the extensive data necessary to make a fully informed determination in full consultation with EPA staff who defined the scope of the Agency's information needs. And EPA conducted its own analysis of data samples and conducted site visits to locations of its own choosing to verify the reliability of the data it had received. From the outset of the study, USWAG and EPRI have worked to inform EPA's decisionmaking by providing all available information. We have done so because we are confident that an informed, science based evaluation will confirm our long held belief that no hazardous waste regulation of FFC waste management units is warranted. It is clearly in our best interest for that decision to be reached as soon as possible  without time consuming clashes over document requests  to remove uncertainty and unwarranted apprehension among our investors, State and local regulators, our employees, and the public that lives near our sites and are our customers. There was simply no reason for EPA to transform a cooperative study into a contentious, adversarial contest. The claim that EPA has neglected its duties by not serving information request letters when that information was already forthcoming is ludicrous. ( USWAG00275) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 25 XIII  25 XIII. WASTE CHARACTERIZATION C. Representativeness of Data Several public interest group commenters argued that the sampling size and statistical analysis of the data used in characterizing FFC waste was inadequate. One of the commenters further compared the site averaged data to published values from literature to support its argument that the comanaged waste data were not adequately representative. The commenter further stated that, based on the literature, EPA should have used higher values in its risk assessment. An industry commenter, on the other hand, characterized the data as the most comprehensive data base ever assembled on the characteristics of FFC wastes.

Response: In terms of sampling size, for FBC wastes and oil combustion wastes, EPA believes the population of facilities sampled was adequate and representative. Sampling data were available for approximately 30 percent of the facilities in these sectors. EPA acknowledges concerns that data were available for a relatively small number of sites for comanaged coal combustion wastes. The Agency, however, is obligated to make use of the best available data. Furthermore, EPA notes that the comanaged waste sites sampled, although few in number, were from a wide range of geographic regions throughout the U. S. They were also representative in terms of the combinations of large volume and low volume wastes comanaged ( see page 3 16 of the Report to Congress).

EPA believes its analysis of the available waste characterization data to be complete and accurate as well as adequate for the intended uses. First, the Agency used all of the available data in its statistical analyses of waste characterization data. Second, the Agency complied with its own Agency wide guidance concerning the analysis of the data, including treatment of the data, calculation of relevant statistics, and appropriate use of quality assurance procedures. Third, no commenters or other parties identified specific instances of problems or issues with EPA's treatment of data. Fourth, no commenters or other parties identified or suggested specific instances where alternate methods of data treatment are more appropriate than those used by the Agency..

In general, the data from EPA's characterization efforts are roughly similar to the literature data cited by the public interest group commenter ( similar means and ranges). This supports the representativeness of EPA's characterization data. The commenter compares the maximum values cited in the literature to the site averaged data presented in EPA's characterization. The Agency points out that the data presented in the literature are not site averaged. Therefore, the maximum values presented represent single sample results that may not be broadly representative of the majority of waste generated over time at a given facility. EPA believes that the use of these single sample maxima in the risk assessment would result in an overestimate of risk. As discussed under Topic XIV. G, EPA believes that site averaging is, for purposes of this study, an appropriate way to generate representative, yet conservative ( i. e., erring on the side of safety), input values for risk assessment. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 26 XIII  26 EPA acknowledges that the input values ( 95th percentile site averages) used in the risk assessment are, as stated by the commenter, similar to the mean values presented in the literature for some constituents. The Agency notes, however, that not only are the data in the literature not site averaged, but the mean values reported in the literature represent the mean of detected concentrations. In its characterization, EPA treated samples reported as below the detection limit as ½ the reported detection limit. The failure to account for samples reported below the detection limit would result in mean values that are not representative of the full range of concentrations that may be present in the waste, particularly for constituents ( such as arsenic) for which a large number of samples may be below detection. Therefore, because they are not site averaged and do not account for samples below detection limits, it is unsurprising the " mean" values in the literature are comparable to the high end values used in the risk assessment. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 27 XIII  27 XIII. WASTE CHARACTERIZATION C. Representativeness of Data Verbatim Commenter Statements EPA candidly admits the data voluntarily provided are too limited for coming to any definitive conclusions regarding their representativeness on a national basis. For coal combustion wastes, the data provided covered onlv 1% of landfill and 3% of impoundments ( 17 facilities in total), and the number of landfills from which the TCLP data were derived " may contribute to uncertainty in these results." ( EDF00021)

The sample size and statistical analvsis of the data used in characterize FFC waste is inadequate. One of the key parameters in the risk assessment is the concentration of the various constituents in the waste. The Agency admits that it is unsure whether the data characterizing the wastes are representative. How could they be representative when less than one percent of the landfills were sampled and less the three percent of the impoundments? EPA has not provided any information to support whether the sampling conducted for the Report adequately characterizes FFC wastes. ( ALA00036)

The wastes are not adequately characterized. The lack of supportive data on the extent to which FFC waste has been characterized in the Report undermines the Report's conclusions and findings with respect to potential impacts on public health and the environment. For example: Only 17 sites and limited samples were used to characterize 600 management sites. The Agency admits that it is unsure whether the data characterizing the wastes are representative. Sophisticated modeling is of no use without adequate input data. ( 49CAO00058)

The limited sampling data used to characterize FFC waste constituents and other serious problems with the site investigations indicates that the concentration range of FFC waste constituents has not been adequately characterized in the Report to Congress. As discussed below, there should be low confidence placed on the database used to characterize FFC waste. ( ALA00292)

We reviewed the peer reviewed literature to check whether other researchers have characterized the constituents of fossil fuel combustion wastes. Table 3 summarizes these findings. for the eight metals included in the EPA analysis as constituents of concern. for coal fly ash and bottom ash. Data were not located in the literature for co managed wastes. We found that for the eight metals selected for review, the values used by EPA are all in the range of published values. However, the facility maximums reported by EPA are all lower than the maximums in the literature for fly ash. For nickel and lead, this difference is more than an order of magnitude. The facility averaged 95th percentile values used by EPA are closer to the mean fly ash values in the literature. Perhaps most importantly, in the draft Report to Congress, the EPA recognizes that " the industry provided contaminant data presented a problem" ( see page l 8 of the Report to Congress). The Report goes on to say: " EPA tested these at up to three times reported levels. but did not test for the possibility Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 28 XIII  28 that even higher levels might exist. Uncertainty still exists as to the nationwide representativeness of this key input variable." Although it is not stated what " reported level" was tested ( i. e., was it the mean, maximum, median?), the data in Table 3 illustrate that, with the exception of cadmium, maximum values reported in the literature ( using fly ash as an example) are significantly higher than 3 times the facility averaged value used by EPA. This suggests that while the industryprovided values used by EPA may represent the high end values for the facilities tested they may underestimate the concentrations found industry wide. ( ALA00292)

Less than 3 percent of the waste management units operating in the U. S. were sampled for the Report to Congress. EPA is relying on only 14 site investigations to characterize  both spatially and temporally  a complex mixture of FFC waste disposed of in waste management units ( WMUs) that varied in size from as small as a few acres to more than 1,500 acres. In addition, these WMUs comanage waste ranging from 1 to 15 different low volume waste streams along with 1, 2, or 3 different large volume wastes. EPA presents no scientific basis to support the notion that the 14 site investigations provide sufficient statistical power to distinguish variations between facilities  or even variations within facilities. It should also be noted that the inadequacy of the analytical monitoring data used to characterize the toxic constituents in FFC waste was consistently identified by EPA and the contractors that conducted both the groundwater risk assessment and the non groundwater risk assessment. ( ALA00292)

These data are the most comprehensive data base ever assembled on the characteristics of FFC wastes and how they are managed as well as the geologic and climatic characteristics of FFC waste management units. EPRl's data collection efforts included in situ samples obtained from 18 sites with active or recently closed management units, as well as porewater samples from drill cores taken from impoundments and landfills used to co manage fly ash, bottom ash, and/ or flue gas desulfurization waste with low volume wastes. Additional data were provided principally through an EPRI study of co management practices, which surveyed 253 active coal combustion waste management units. This study was developed in consultation with EPA staff to ensure the quality and representativeness of the data. See USWAG Initial Comments at 22 23. ( USWAG00275) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 29 XIII  29 XIII. WASTE CHARACTERIZATION D. Adequacy of TCLP and EP Tests Industry, academic, and public interest group commenters questioned whether the TCLP test adequately represents the leachate from FFC wastes. Commenters variously expressed concern that the TCLP may underestimate or overestimate the leaching of the various waste constituents. Specific concerns raised were that: the TCLP underestimates the leaching potential of alkaline wastes; the TCLP underestimates leaching in acidic environments such as might be created by mill rejects; the TCLP does not adequately represent long term leaching following ettringite formation; and the EP test was found to be inadequate by the SAB in 1991. Another commenter pointed to the SAB's recommendations about revising the TCLP. One of the commenters stated that TCLP or EP tests would not be appropriate unless FFC waste were disposed in a municipal landfill. Another commenter suggested that long term leaching tests using a solution approximating percolating ground water would be more appropriate and accurate.

One industry commenter supported the use of the TCLP as a reflection of probable leaching conditions in soil amendment applications of CCW, but stated that the TCLP may overstate leachate concentrations in minefill operations. This commenter concluded that it is neither surprising nor relevant to the determination that the TCLP may not perfectly model leaching behavior in every waste and in every application.

Response: The Agency acknowledges that the TCLP is designed to simulate the leaching conditions found at a typical municipal solid waste landfill and that conditions in FFC waste management units may be different from those in municipal solid waste landfills. EPA has no evidence, however, to indicate that these differences are significant enough to invalidate TCLP or EP test results as reasonably representative of FFC waste leachate. Furthermore, for many of the waste types studied, the only leaching test results available to EPA were TCLP and/ or EP results. In the one case where EPA had porewater data for comanaged coal combustion wastes in surface impoundments, the Agency made use of these data in its characterization and risk assessment. For other wastes and management scenarios, EPA made use of the best available leachate characterization data, which were TCLP and/ or EP data. The Agency notes that most of the commenters did not provide any suggestion as to leaching procedures that would be more accurately representative. Some commenters did recommend alternate leaching test procedures, including a synthetic ground water leach procedure and an ASTM leach extraction procedure.

EPA agrees that results of long term leaching using a solution designed to simulate ground water would be a useful tool in waste characterization. However, insufficient amounts of such data were available for this study. Furthermore, the resources required to develop site specific methods and collect and evaluate such data likely would be prohibitive. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 30 XIII  30 XIII. WASTE CHARACTERIZATION D. Adequacy of TCLP and EP Tests Verbatim Commenter Statements Perhaps in an effort to minimize the inappropriate use of TCLP data in this case, EPA does not provide the pH of the coal combustion or other fossil fuel combustion wastes that are described in the current Report to Congress, on either an as generated or co managed basis. However, in the general descriptions of low volume coal combustion wastes provided, the Agency notes boiler chemical cleaning waste and water treatment wastes exhibit the corrosivity characteristic, and thus may have a pH greater than or equal to 12.5. See 1999 Report to Congress, Table 3 5. And in the earlier Report to Congress, EPA indicated dual alkali FGD sludge has a pH of 12.1, and boiler blowdown has a pH of up to 12.0. See 1988 Report to Congress, Exhibits 3 17, 3 20. ( EDF00021)

First, EPA consistently relies upon TCLP data as the waste contaminant concentration input to the groundwater model for landfills and some surface impoundments ( where pore water sample data were unavailable), regardless of whether the leaching procedure accurately measures the leaching potential of the wastes under consideration. For example, EPA is fully aware that the TCLP seriously. understates the leaching potential of highly alkaline wastes. Although some coal combustion wastes under consideration ( and perhaps others as well) are highly alkaline, EPA still uses TCLP data in the groundwater model. Moreover, at least one of the low volume wastes ( coal mill rejects) can become reactive if sufficient concentrations of pyrites are present. ( EDF00021)

Moreover, at least one of the low volume wastes ( coal mill rejects) can become reactive if sufficient concentrations of pyrites are present. Over time, these wastes can present " acid causing conditions" at some disposal locations. Yet there is absolutely no discussion in the Report as to whether TCLP data can be used to represent reasonable worst case waste leachability under such acidic disposal conditions. ( EDF00021)

A good indication of the weakness of the TCLP for the wastes in question can be found in Table 3 9 of the Report to Congress. In this table, EPA provides TCLP data ( covering wastes in both landfills and surface impoundments) and pore water sample data ( covering surface impoundments) for co managed coal combustion wastes. For every toxic contaminant but mercury, both the mean and upper range of the pore water data exceed the TCLP data, typically by an order of magnitude or more. In the case of arsenic wastes, a particularly important contaminant in coal combustion the difference between the mean pore water and TCLP data is almost two orders of magnitude. Insofar as the pore water data represent " actual leachate" results for surface impoundments, it is clear that the TCLP data consistently fail to predict the actual concentration of contaminants available for migration into groundwater. ( EDF00021)

EPA cannot simply rely upon the TCLP because it is the test used in the current toxicity characteristic. The procedures employed in EPA's risk modeling must bear some rationale relationship to anticipated disposal conditions, particularly where the TCLP underpredicts waste Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 31 XIII  31 leachability and therefore is not a valid indicator of " potential" risks. See Columbia Falls, supra, at 922 3. ( EDF00021)

While EPA claims TCLP data " are believed" to better represent leaching conditions in landfills, it never explains the reasons for this belief. Report to Congress at 3 18. In fact, the TCLP data in Table 3 9 are provided for both landfills and surface impoundments, and appear to be dominated by surface impoundments given the Agency's concern that " a much smaller number of landfills are reflected in the data." Report to Congress. ( EDF00021)

In the groundwater risk assessment, concentrations may not be reflective of actual conditions due to the tests used. Specifically, the tests used to estimate the extent to which the metals leach from the waste may be inadequate. EPA has not demonstrated that the leachate tests ( Toxicity Characteristic Leaching Procedure, TCLP) for landfills and leachate represented by pore water samples for impoundments is adequate for risk assessment. In a February 26, 1999 memo from the Science Advisory Board's ( SAB) Environmental Engineering Committee to the Administrator, the SAB reminds EPA that in 1991 the SAB recommended improvements to leaching test procedures. The Agency has not used the SAB's recommendations to revise the TCLP or to develop other protocols. Use of the TCLP may underestimate or overestimate the leaching of the various waste constituents. The SAB subcommittee noted that leach testing needs to account for more leaching parameters because these parameters have a direct affect on actual leaching of contaminants from waste in the field. The important point is that the Agency should have low confidence in the waste characterization because the small data set and the leachate test results may not be representative of real world facilities. ( ALA00036)

Since significant alteration of chemistry and mineralogy is exhibited by certain classes of FFC wastes, it is imperative that testing methods used to evaluate the potential for adverse environmental impact be flexible and up to date to incorporate state of the art scientific understanding. Leaching characterization, for example, should incorporate long term equilibration times to allow for potential mineralogical changes such as formation of ettringite to take place and should utilize a leaching solution that reflects what would happen at specific sites. The toxicity characteristic leaching procedure ( TCLP) and extraction procedure ( EP) toxicity test procedures using acetate buffer or dilute acetic acid with an l8 hour equilibration time would likely never be appropriate unless FFC wastes were to be disposed in a sanitary landfill. ( EERC00044)

It is unfortunate that the EPA chose to use TCLP as the test for evaluating wastes from FFC. It has been demonstrated and it is well known that many FFC wastes, especially alkaline types from combustion of lower rank coals or from advanced coal combustion processes such as fluid bed combustion, undergo chemical and mineralogical transformations upon contact with water. One important mineral that is often formed during the hydration of alkaline or lower rank CCBs is the mineral ettringite ... If the proper concentrations of components are provided along with high alkalinity, ettringite forms readily. These conditions are often met when low rank CCBs contact water. The ash in most cases has all of the potential ingredients for ettringite formation and it has Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 32 XIII  32 been found that many low rank CCBs do form ettringite as a primary hydration product ... A shortterm leaching test of 18 hour duration such as the TCLP or American Society for Testing and Materials ( ASTM) water shake test may be concluded before ettringite has even begun to form in some CCBs. This could result in highly misleading information regarding leachability of several very important and potentially problematic trace elements. Since these transformations can chemically fix certain trace elements, particularly those that exist in aqueous solution as oxonians such as arsenic, boron, chromium, molybdenum, selenium, and vanadium, and because these chemical and mineralogical transformations can take up to months, TCLP is clearly an inappropriate test for evaluation of wastes from FFC in monofills. ( EERC00044)

Alternative tests to the TCLP exist that are more appropriate. One of these, the ASTM shake extraction, and another, the synthetic groundwater leaching procedure ( SGLP) developed at the University of North Dakota ( Hassett, 1987), can provide more relevant data, especially if leachate concentrations are measured over time periods of up to 2 months and greater. Potentially problematic trace elements, including those listed above, have been found to decrease in concentration over time ( Hassett, 1991; Hassett, 1994). The use of an acetate based short term leaching is clearly inappropriate. Although the TCLP is appropriate for wastes in sanitary landfills, FFC wastes, often disposed in monofills, require a different approach. The argument that the TCLP, being acidic in nature, represents a worst case scenario is also a fallacy. SGLP or ASTM leaching do not provide data that can be generally characterized as higher or lower in quality, but rather as more scientifically valid and legally defensible. Alternative and more scientifically valid procedures such as the EERC's SGLP and the ASTM shake extraction test are also in line with the performance based measurement system ( PBMS) approach to compliance monitoring recently initiated by EPA. Since leaching data on FPC wastes generated using TCLP or other short term leaching tests may be flawed, care must be exercised in the application of these data for environmental impact projections or modeling. ( EERC00044)

The toxicity characterization of the wastes relied on two tests, one of which the EPA's own Science Advisory Board in 1991 noted was inadequate. ( 49CAO00058)

Among the findings of the Boulding report, which was based on extensive literature review and analysis of coals burned in Indiana utilities ( including Kentucky coals), that bear on the EPA assessment of the risks associated with coal combustion waste ( CCW) disposal, are these ... 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. ( NCCLP00282)

Many of the elements they feel will be ` locked up' in the high pH of ashes for instance, in reality leach out easily at high pHs, as well as at the more acidic. ( PEACE00306) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 33 XIII  33 Certain cornmenters have attacked the TCLP test as a flawed methodology. TCLP was designed to approximate the behavior of metals in a typical landfill environment. TCLP reflects probable leaching characteristics in soil amendment application of coal ash. However, TCLP probably overstates the concentration of toxics in leachate from mine reclamation and minefilling, because the alkalinity of the FBC ash and its pozzolonic ( cement like) nature, combined with the compaction in the backfilling process, will decrease the mobility of metals significantly, in contrast to a landfill disposal. PG& E Gen has documented compaction densities in FBC ash reclamation projects that achieve permeability rates of less than 10 6 crn/ sec or better, approaching the permeability requirement for municipal solid waste landfill liners. ( See also, attached geotechnical report for additional information on compaction density of FBC ash fill.) Thus, TCLP data most likely significantly overstates the actual leachability of toxics from FBC ash in the mine reclamation context. Equally important, TCLP is the bright line test for waste toxicity for all wastes and all uses established by EPA. That TCLP may not perfectly model leaching behavior in every waste and in every application is neither surprising nor relevant to this determination. ( PG& E00274) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 19 FF2P S0367.

34 XIII  34 XIII. WASTE CHARACTERIZATION E. Characterization of Mercury Several public interest group commenters suggested that EPA's characterization of mercury was inadequate, with some of the commenters suggesting the characterization failed to even test for mercury. The commenters found the lack of attention to mercury egregious in light of the perceived risks, the current attention to mercury throughout the Agency, and the high levels of mercury emissions from utilities.

Response: The Technical Background Document for the Report to Congress on Remaining Wastes from Fossil Fuel Combustion: Waste Characterization19 does present characterization data on mercury. Specifically, leachate and/ or porewater mercury data were presented in Tables 3 15 and 3 16 for comanaged wastes, Tables 3 18 through 3 23 for oil combustion wastes, and Tables 3 24 through 3 28 for FBC wastes. Whole waste mercury concentration data were presented in Tables 2 10 through 2 12 for oil combustion wastes and Tables 2 13 through 2 15 for FBC wastes. For comanaged wastes, only one site reported whole waste mercury concentration, a single sample below a detection limit of 0.13 milligrams per kilogram ( mg/ kg). EPA used these characterization data for mercury in its risk assessment as discussed below under Topic XIV. C. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 35 XIII  35 XIII. WASTE CHARACTERIZATION E. Characterization of Mercury Verbatim Commenter Statements EPA did not adequately characterize FFC wastes, including mercury releases. ( ALA00036)

The waste characterization analyses fail to even test for mercury, or if they do, the report fails to present the data. If the data were available, it would be possible to calculate the mercury content of and mercury fluxes from the various wastes streams. ( ALA00036)

It appears that the waste characterization analyses fail even to test for mercury. ( 49CAO00058)

EPA requested analyses for mercury, however the EPRI contractor did not collect or preserve samples for mercury analysis and none were done. ( ALA00292)

In addition, the field sampling, as documented by SAIC did not follow the QAPP decontamination procedures, nor was the complete list of target analytes analyzed for ( e. g., mercury and chromium ( VI)). ( ALA00292)

Mercury was not modeled in the human health assessment portion of the non groundwater analysis. One reason for this is that mercury was not reported in the co managed waste analytical data. This shortcoming is noted above in the waste characterization section  the EPRI contractor did not collect or preserve samples for mercury analysis although mercury is specified in the QAPP as a target analyte. ( ALA00292) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 36 XIII  36 XIII. WASTE CHARACTERIZATION F. Characterization of Organics, Radionuclides, and Dioxins/ Furans Public interest group and academic commenters argued that EPA's characterization data for organics, dioxins and furans, and/ or radionuclides were inadequate and/ or inadequately presented. Particularly, some of the commenters suggested that the characterization was insufficient to rule out these constituents from risk assessment. One of the commenters was particularly concerned about polycyclic aromatic hydrocarbons ( PAHs) and phenols. Another commenter suggested that FBC wastes retain volatile and semi volatile organics in the bottom ash to a greater extent than conventional pulverized coal combustion wastes.

Response: EPA based its characterization of organic constituents ( including dioxins and furans) on the following sources:

° Inorganic and Organic Constituents in Fossil Fuel Combustion Residue, Volume 1: A Critical Review. Electric Power Research Institute. EP 5176. August, 1987. ° Development Document for Effluent Limitations Guidelines and Standards and Pretreatment Standards for the Steam Electric Point Source Category. EPA, Office of Water. EPA 44/ 1 82/ 029. November, 1982. ° PCDDs and PCDFs in Coal Combustion By Products ( CCBS). Final Report. Electric Power Research Institute. March, 1998. ° Organics data reported in the Fossil Fuel Fluidized Bed Combustion By Products Survey electronic database provided by the Council of Industrial Boiler Owners. ° Organics data reported in the Oil Combustion By Products Database provided by the Electric Power Research Institute. ° Letter to Dennis Ruddy, EPA, from James R. Lindsay, Florida Power and Light, transmitting analytical data for split samples at FPL's Riviera Facility. June 18, 1997.

Based on these sources, EPA concluded that organic constituents, including PAHs, are infrequently present in FFC wastes at levels above analytical detection limits. This conclusion is consistent with the expectation that organics are destroyed in the combustion process or pass out the stack. Given this conclusion, the Agency did not consider organics in its risk assessment. EPA also did not include a detailed summary of the organics characterization data from these sources in the docket, because any such summary would consist primarily of non detects. EPA does not disagree that there is a possibility that FBC combustion conditions might result in wastes that retain organics to a greater extent than conventional coal combustion wastes. The analytical data for FBC wastes, however, still show that organic constituents are rarely present above analytical detection limits.

EPA based its characterization of radionuclides on a variety of sources, as discussed under Topic XI. A ( see the report in the docket " Review of Literature on Radionuclides in Fossil Fuel Combustion Wastes). To avoid duplication of effort with the more detailed study of radionuclides Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 37 XIII  37 in FFC wastes being conducted by the Office of Air and Radiation, the Agency did not consider radionuclides in its risk assessment or present a detailed summary of radionuclides data in the docket. EPA has reviewed rationuclide concentrations in coal and ash in connection with other regulatory programs ( EPA1989a, 1989b, 1995c). One of these studies examined potential exposures of worker and nearby resident to ratioactivity from ash released from a coal pile through wind and runoff erosion. Exposure from direct contact, inhalation, and ingesiton were estimated to fall below natural background ratiation exposure levels even for a worker standing on the ash pile ( EPA, 1989a). In addition, EPA is currently studying coal combustion wastes as part of a larger study of naturally occurring radioactive materials UNORM). The report from this NORM study is expected to be published later in 2000. Due to the low expected risks associated with nadionuclides in coal ash, and to prevent duplicaiton of effort with the NORM study, EPA eliminated radionuclides from further consideration in this study. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 38 XIII  38 XIII. WASTE CHARACTERIZATION F. Characterization of Organics, Radionuclides, and Dioxins/ Furans Verbatim Commenter Statements Data are not presented in the Report on the analyses of the concentration of organic compounds or radioactive substances in FFC waste; however, EPA determined that no public health concem exists from these potentially toxic constituents. It is particularly important that organic emissions, including dioxins/ furans, that can be generated when coal is combusted with other materials such as tires, used oil, railroad ties, and sewage sludge ( i. e. cobuming) be carefully considered in the risk assessment. EPA states on page 3 13 of the Executive Summary that " although an exhaustive review of the organics data has not been conducted, based on available information; total and leachable organics are generally reported to be at or below analytical detection limits." ( ALA00036)

Data on organic or radioactive substances in the wastes are not reported, although EPA concludes that they represent no human health risks. ( 49CAO00058)

As with PAH's the draft Determination relies on a few reports by third parties to dismiss the existence and environmental threat of radioactivity without sufficient justification. Dismissing the need to analyze for or monitor such constituents on financial or technical grounds is not valid. ( HEC00332)

Considering the lack of testing or monitoring for phenols at other ash sites around the country , further consideration and study of the presence of phenols in CCW is needed. ( HECL0014)

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. ( NCCLP00282) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 39 XIII  39 XIII. WASTE CHARACTERIZATION G. Impacts of HAP/ NOx Regulations Public interest group commenters argued that EPA had not considered the effect on waste characteristics of upcoming requirements under the Clean Air Act. The commenters suggested changes in air pollution control technology would cause metal concentrations in waste to increase.

Response: We have carefully considered the issue of cross media impacts and the commenters' specific concerns that future air regulations could have an adverse impact on the characteristics of coal combustion wastes. We have concluded that it is premature to consider the possible future impact of such new air pollution controls on the wastes that are subject to today's regulatory determination. The Agency plans to issue a regulatory determination in the latter part of 2000 regarding hazardous air pollutant ( HAP) controls at coal burning, power generating facilities. If EPA decides to initiate a rulemaking process, final rulemaking under the Clean Air Act is projected to occur in 2004. Thus, no final decision has been made on what, if any, constituents will be regulated by future air pollution control requirements. Additionally, the regulatory levels of the those specific pollutants that might be controlled and the control technologies needed to attain any regulatory requirements have not yet been identified. Therefore, we believe there is insufficient information at this time for evaluating the characteristics and potential environmental impacts of solid wastes that would be generated as a result of new Clean Air Act requirements.

When any rulemaking under the Clean Air Act proceeds to a point where we can complete an assessment of the likely changes to the character of coal combustion wastes, we will evaluate the implications of these changes relative to today's regulatory determination and take appropriate action. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 40 XIII  40 XIII. WASTE CHARACTERIZATION G. Impacts of HAP/ NOx Regulations Verbatim Commenter Statements Nor has EPA taken into account the anticipated increases in metal concentrations of pollution control wastes associated with upcoming requirements promulgated under the Clean Air Act. ( EDF00021)

The Report and its risk assessments do not address the changing characteristics of fossil fuel wastes that may result from attempts to comply with new air pollution control standards. For example, there is no discussion of the effects of installing controls for nitrogen oxides on the character of the coal combustion waste that would be produced by utility coal fired power plants and its potential for harming the environment. With more time to comment we hope to submit a detailed analysis of the risk assessments done for this Report. ( HEC00056)

Currently, there is a growing nationwide movement to place mercury emission controls on coalfired plants. If these controls are enacted, mercury concentrations will rise in CCW as more mercury is retained in the ash. Without responsible CCW disposal standards, emissions standards will not prevent mercury contamination from degrading the environment. We will only be changing the pathway by which it enters our streams and lakes. The impacts of mercury from CCW and higher concentrations of mercury in CCW created by mercury emission controls needs to be further studied by EPA. ( HEC00332) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 41 XIII  41 XIII. WASTE CHARACTERIZATION H. Characterization of Mill Rejects One industry commenter contended that the Report's statement that coal mill rejects could " potentially" be reactive is mistaken because coal mill rejects do not emit any gases and fumes.

Response: The Agency has not conducted a detailed evaluation of mill rejects with regard to the RCRA characteristic of reactivity. EPA's primary concern with mill rejects is that, if not properly managed, their pyritic component has the potential to generate acid that can mobilize constituents in comanaged wastes. This concern is addressed under Topic IV, above. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 42 XIII  42 XIII. WASTE CHARACTERIZATION H. Characterization of Mill Rejects Verbatim Commenter Statements EPA's speculation that coal mill rejects could " potentially" be reactive is mistaken. This potential in fact is nonexistent because coal mill rejects do not emit any gases and fumes. EPA should correct this misstatement in the final regulatory determination. ( USWAG00037) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 20 FF2P S0092. Memorandum to Dennis Ruddy, EPA, Regarding Corrected Final EPA/ EPRI Analytical Data Assessment and Comparison. Ray Anderson and Chris Long, SAIC. August 13, 1997.

43 XIII  43 XIII. WASTE CHARACTERIZATION I. Sampling and Analysis Quality Assurance One public interest group commenter stated that sampling, handling, and analysis procedures utilized by the industry contractor performing the waste characterization analysis did not conform to EPA's protocols adopted for the study, and potentially biased the outcomes.

General Response: EPA acknowledges that there were certain deviations from the procedures specified in the Quality Assurance Project Plan ( QAPP) at three sites where EPA performed verification sampling in conjunction with industry sampling efforts. The Agency notes, however, that these deviations were noted only at three sites, not at all of the sites sampled by the industry. Furthermore, EPA compared the results of the industry sampling at these sites to its own analytical results from split samples at these sites. As documented in the docket, 20 EPA found a high degree of comparability between the EPA and EPRI results, suggesting that the data are valid and representative. Finally, many of the deviations from QAPP procedures noted, if significant, would tend to overestimate, not underestimate, contaminant concentrations. Thus, EPA does not believe that the minor deviations in procedures found at three sites are sufficient basis to invalidate the representativeness and conservatism of the characterization of FFC wastes used in this study. Specific problems with data collection and analysis cited by the commenter are identified in the numbered items below, with specific responses to each item.

1. At the FP& L site, no field quality control samples were taken and there was no decontamination of equipment.

Response: Field quality control samples were taken and equipment decontamination was conducted at the FP& L site. The commenter's concern appears to be based on a misinterpretation of the information presented in a memorandum describing the field activities at the site. The statements in this memorandum were intended to indicate that there were no issues noted with the field quality control samples and equipment decontamination, not that these activities were not conducted. The Agency apologizes if the presentation of the information was unclear.

2. At three other sites, field blanks were used as both field blanks and equipment blanks.

Response: Chapter One of EPA's " Test Methods for Evaluating Solid Waste SW 846" does not specifically recommend the inclusion of field blanks in the suite of field QC samples. SW 846 does, however, recommend the use of equipment ( rinsate) blanks. The blanks in question were useful as equipment blanks because each water sample was collected after it passed through or over ( i. e., rinsed) the sampling equipment. The Agency's own QAPP for the verification Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 44 XIII  44 sampling effort did not call for the use of field blanks, and we are not concerned about the lack of field blanks in the verification sampling effort.

3. Reagent grade water was not used for blank water; locally purchased distilled water was used instead at two sites.

Response: Reagent grade water is preferred for use as blank water because the quality of the water is know prior to its use. While quality of the locally purchased distilled water was not known in advance, the sample analysis results for the blanks indicate that the water was of adequate quality for its intended use. For example, constituents of concern ( As, Se, Cr, and Fe) were not detected at or below the reporting limit in any of the field/ equipment blank samples with the exception of chromium which was detected in two of the blanks at concentrations just greater than the detection limits.

4. At three other sites, the EPRI team failed to perform equipment decontamination in accordance with the EPRI work plan.

Response: The deviations in equipment decontamination procedures noted could cause the sample analysis results to be biased high ( i. e., increase the concentration of contaminants in the sample) if the procedure failed to remove chemical or material contamination from the sampling equipment. The sample analysis results for the field/ equipment blanks indicate most constituents of concern were either not detected or detected at concentration near the detection limits for the constituents of concern in the blanks. The Agency notes that even if the deviations from the decontamination procedures did introduce bias, such bias would only result in an overestimate, rather than underestimate, of contaminant concentrations thus leading to a more conservative ( i. e., erring on the side of safety) waste characterization for the three sites.

5. The samples for iron speciation were preserved incorrectly, therefore rendering useless the speciation analysis for iron.

Response: EPA acknowledges that, because of issues with the sample preservation, its contractor laboratory ( Columbia Analytical) did not perform iron speciation analyses. This lack of iron speciation data, however, had no significant impact on EPA's waste characterization, as iron speciation was not considered as part of the risk assessment.

6. The sample volume collected by the EPRI contractor for sample splits was only 200 : L, rather than the typical 5 liter volume required to obtain the lowest achievable detection limits and the standard quality assurance analyses of duplicate and spike samples. Neither the EPRI contractor nor EPA's independent contractor could perform all of the quality assurance procedures, because the small sample size collected by the EPRI contractor precluded the analysis of duplicate or spike samples. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 45 XIII  45 Response: Because EPA substituted ½ the detection limit for analyses reported to be below a detection limit, the inability to obtain the lowest achievable detection limits would result in an overestimate of contaminant concentrations, except in cases where the actual concentration was greater than ½ the achieved detection limit and greater than the lowest achievable detection limit. Because this concern applies only in these cases and only at three sites, the effect on EPA's overall characterization is not likely to be significant.

EPA's analysis of field duplicates for the three sites indicated that the laboratory analytical systems were operating efficiently and could effectively reproduce the sample concentrations. Therefore, the inability to perform all the analyses of duplicate and spike samples is not a major concern.

7. The EPRI contractor lab had detection limits for 8 metals that were between 25 and 10,000 times higher than the independent EPA lab. This discrepancy cannot be explained, as both labs used identical procedures.

Response: In response to EPA's concerns about the differences between detection limits, the industry contractor lab ( Battelle) provided an explanation for the differences. The difference appears to be based on methodology used to determine the detection limit. Battelle detection limits are set based on analyses of standard samples where the repeated analyses of lowest standard produces a large variability in measure concentrations ( 25 to 50 percent), as opposed to using high concentration standards. Furthermore, most of the positive results reported by the EPA contractor lab ( Columbia Analytical), where Battelle reported results below the detection limit, should be considered trace level concentrations that were slightly above the Columbia detection limit. Therefore, given the very good agreement between results from the two labs overall, EPA does not consider the difference in detection limits to be a critical concern. As discussed above, given EPA's characterization methodology, the higher detection limits are more likely to result in conservative estimates of concentration ( i. e., overestimates). Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 46 XIII  46 XIII. WASTE CHARACTERIZATION I. Sampling and Analysis Quality Assurance Verbatim Commenter Statements For example, the record demonstrates that EPA was/ is aware ( as documented in various memoranda in the docket) that data sampling, handling, and analysis procedures utilized by the industry contractor performing the waste characterization analysis did not conform to EPA's protocols adopted for the study, and potentially biased the outcomes. ( ALA00292)

In the course of this work our consultants discovered that the Agency was aware of serious flaws in the data collection and analyses underlying the Report and the Regulatory Determination, but chose to go ahead despite these issues. ( ALA00292)

In fact, numerous data collection and analysis problems are documented by SAIC in the record underlying the Report to Congress. It is clear that the sample collection and analysis activities did not meet the data quality objectives outlined in the QAPP, as set forth in more detail below. This calls into question the quality and accuracy of the results of the waste characterization analyses. Two memoranda to the docket document the site visits to the four power plants. Both memoranda point out problems with the field activities. At the FP& L site, no field quality control samples were taken and there was no decontamination of equipment. At the other three sites, more serious problems were observed by SAIC as summarized below:

° Field qualitv control samples. Field quality control samples differed from those specified in the EPRI work plan and the QAPP. Field blanks were used as both field blanks and equipment blanks, an approach that differs from EPA guidance. Also, reagent grade was not used for blank water; locally purchased distilled water was used instead at two sites. ° Equipment decontamination. The EPRI team failed to perform equipment decontamination in accordance with EPRI work plans... ° Iron speciation. The samples for iron speciation were preserved incorrectly, therefore rendering useless the speciation analysis for iron. ° Sample volume. The sample volume designated by the EPRI contractor for sample splits was only 200 m1, rather the typical 5 liter volume required to obtain the lowest achievable detection limits and standard quality assurance analyses of duplicate and spike samples. ( ALA00292)

Neither the EPRI contractor nor EPA's independent contractor could perform all of the quality assurance procedures, because the small sample size collected by the EPRI contractor precluded the analysis of duplicate or spike samples. Furthermore, with regards to the duplicate samples that were analyzed by the Independent laboratory, the EPRI contractor lab had detection limits for 8 metals that were between 25 and 10,000 times higher than the independent lab. ( This discrepancy cannot be explained, as both labs used identical procedures). The result of this is that the EPRI Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 47 XIII  47 contractor reported non detectable concentrations for the eight metals, compared to positive concentrations reported by the independent lab ... In summary, our review of the QAPP requirements for this project, and other docket materials reveals that the sampling methods and the analyses performed on the waste samples do not meet the data quality objectives in at least the following areas: accuracy, precision, and completeness. In addition, the field sampling, as documented by SAIC did not follow the QAPP decontamination procedures, nor was the complete list of target analytes analyzed for ( e. g., mercury and chromium ( VI)). ( ALA00292) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 21 FF2P S0048. Effect of Pore Size of Filters on the Observed Aqueous Concentrations in Filtrates. Draft Report. EPRI. June, 1997.

48 XIII  48 XIII. WASTE CHARACTERIZATION J. Filtration of Samples One public interest group commenter expressed concern with the filtration of ground water and low volume waste samples at three sites, and the filtration of ground water and porewater samples at another site. The commenter stated that the filtration performed by the industry contractor in these cases was inconsistent with EPA guidance and likely to bias the results low.

Response: EPA initially expressed concern with the filtration of samples early on in the study process. In response, EPRI conducted a study of the effects of filter pore size on observed concentrations at the sites where filtration was conducted. This study is included in the docket. 21 This report compared concentrations in 0.0007 : m filtrates with those in 0.45 : m filtrates and found that in almost all samples the percentage difference between the observed concentrations in the two different filtrates was far less than 25 percent and within the experimental error. Based on these results, EPA does not believe that the filtration of samples biased the results low. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 49 XIII  49 XIII. WASTE CHARACTERIZATION J. Filtration of Samples Verbatim Commenter Statements At the other three sites, more serious problems were observed by SAIC as summarized below ...

° Filtration of ground water samples. The field procedures observed were inconsistent with EPA guidance recommending against the filtration of ground water samples prior to analysis for metals ( although consistent with EPRI work plans). The aggressive filtration step used by the EPRI contractors for the groundwater samples is likely to bias the results low, so that the metals concentration detected may not represent the total mobile contaminant loading on the aquifer. ° Filtration of aqueous waste sampIes. EPRI contractors pressure filtered all low volume waste samples. This approach is inconsistent with EPA methodologies. SAIC expressed concern that filtration to this extent could bias the results low because mobile contaminants associated with colloid sized particles would be concluded from the analysis. ( ALA00292)

The filtration issue is critically important and is reiterated by SAIC in a different memorandum to EPA regarding a draft EPRI site report. In that memorandum, SAIC writes that the most significant concern regarding the data in the report relates to the 3.6 nanometer filtration step performed on porewater samples and ground water samples. Filtration to this level will remove porewater components capable of movement through the groundwater, In short. SAIC states that the porewater samples and groundwater samples may be expected to consistently underestimate the metals concentration and will lead to an underestimation of the contribution of the waste unit leachate to the surrounding groundwater. ( ALA00292) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 50 XIII  50 XIII. WASTE CHARACTERIZATION K. Characterization of Chromium VI One public interest group commenter stated, although EPA requested data for the hexavalent species of chromium, the industry failed to provide this data, and that the characterization and risk assessment therefore failed to adequately consider chromium.

Response: The commenter is correct that speciated data were not available for chromium. Ample data, however, were available on total chromium concentrations. To account for the lack of speciated data, EPA's risk assessment made the conservative assumption that all chromium present was in the more toxic hexavalent state. Thus, the characterization and risk assessment adequately and conservatively considered chromium. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 51 XIII  51 XIII. WASTE CHARACTERIZATION K. Characterization of Chromium VI Verbatim Commenter Statements EPA requested analysis for chromium ( VI) however the EPRI contractors did not collect these samples. ( ALA00292)

In addition, the field sampling, as documented by SAIC did not follow the QAPP decontamination procedures, nor was the complete list of target analytes analyzed for ( e. g., mercury and chromium ( VI)). ( ALA00292) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 1 XIV  1 Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 2 XIV  2 XIV. RISK METHODOLOGY IN GENERAL A number of commenters expressed concern about the methodology used by EPA in the risk assessment process. Specific concerns included the level of conservatism inherent in the methodology, the specific constituents considered, the methodology for considering risks to children, the selection of toxicity benchmarks, the specific values used for arsenic toxicity, the use of site averaging and inclusion of data from certain sites in selecting source terms, and the adequacy of coordination between various parts of the risk assessment. These concerns are all addressed below.

The focus in these comments was on risk modeling, not on the overall weighing of modeling, state programs and damage cases in the final risk characterization underlying today's decision. EPA wishes to point out, again, that groundwater modeling was not used as a basis for today's decision; yet, in an effort to clarify certain questions below address many groundwater modeling related issues.

Response: EPA believes its overall risk modeling methodology was appropriately protective ( erring on the side of safety), based on state of the art science, and adequately coordinated and fully peer reviewed. Four peer reviewers examined those aspects of the risk assessment within their areas of expertise. EPA believes it appropriately considered all of the constituents of greatest concern based on the available characterization data. EPA believes it appropriately selected toxicity benchmarks and that its use of site averaging, described in Section XIV. G below, was reasonable and appropriate. The Agency agrees that there is substantial uncertainty surrounding the values used for arsenic toxicity, but believes it applied values based on the best available current scientific knowledge ( See Sections VIII and XIV. F below.) These and other specific concerns raised by the commenters with regard to risk assessment methodology are addressed in more detail in the sub topic responses below.

The essence of this section is that EPA received comment that we both over and underestimated risk in our risk modeling. EPA used the data available and conducted risk modeling in accordance with practices developed for past rulemakings. It is important to note here that EPA is reviewing its groundwater model in response to specific comments. We have not yet reached conclusions based on our review. Iif this review warrants, groundwater risk modeling will be revisited. Specific comments are addressed below. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 3 XIV  3 XIV. RISK METHODOLOGY IN GENERAL Verbatim Commenter Statements It appears that EPA's modeling effort has created, in EPA's attempt to be conservative, an unrealistic scenario for the use of FBC ash. The extreme conservatism has resulted in the application of unreliable, mutually exclusive data that, on occasion, results in scenario parameters that break basic scientific principals. Selecting the input parameters more carefully in order to more realistically represent even extreme conditions for managed FBC ashes should dramatically change the outcome of the Report and position of the EPA on FBC ash. ( ARIPPA00019)

There seems to be some concern with regard to the actual assumptions that went into assigning the toxicity to arsenic that clearly needs to be evaluated. ( ARIPPA00019)

The risk analyses undertaken thus far regarding FFCW are grossly inadequate. The methodologies employed to date involved incomplete and/ or invalid data and risk modeling, resulting in substantial understatements of actual and potential risks. ( EDF00021)

Key deficiencies include the following ... methodology used to estimate potential risks via the groundwater pathway which systematically and substantially understates such risks due to reliance on TCLP data for highly alkaline wastes, the use of facility averaged TCLP data instead of actually measured high end values, and myriad technical deficiencies identified in the modeling itself. ( EDF00021)

The EPACMTP's risk assessment model significantly overestimates the risk to human health theoretically presented by potential releases from combustion ashes into the environment. ( PG& E00023)

Moreover, as demonstrated in the bulk of the testimony delivered at the agency's May 21 public hearing on the Report, these results would occur despite the fact that the agency's risk analysis seriously overstates the alleged risk from arsenic in CCPs. ( NMA00024)

PCA shares the US Department of Agriculture's concerns about the risk assessment methodologies and assumptions used by EPA in evaluating risks. ( PCA00034)

The assumption used in the exposure assessment and toxicity assessment could significantly underestimate the quantitative risk estimates reported by EPA. ( ALA00036)

Unfortunately, the overly conservative assumptions and simplified modeling methodologies resulted in numerical risk estimates that do not comport with real world observations. ( USWAG00037) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 4 XIV  4 In 1997 USWAG commented on EPA's proposed risk analysis methodology for the Phase II Bevill study, and in 1998 USWAG commented in detail on the " revised draft final" groundwater pathway risk assessment. Those comments sounded three consistent themes: ( 1) EPA should utilize the wealth of real world data to the fullest extent possible; ( 2) when modeling is necessary, EPA should avoid excessively conservative assumptions that undermine the validity of its conclusions; and ( 3) EPA should validate its modeling results by comparison with real world data. USWAG's previous criticism of EPA's modeling based risk assessment remain valid, and we incorporate them here in full. ( USWAG00037)

The EPA expressed concern regarding the groundwater pathway risk associated with arsenic from the land disposal of comanaged FFC wastes from coal fired utilities. USWAG comments provide detailed, technical information demonstrating the risks are overstated by several orders of magnitude. Reiteration of the technical arguments is unnecessary. However, APS strongly agrees with USWAG's position ( APSC00043)

The methodology used in the risk assessment that is based on EPACMTP modeling, is fundamentally flawed. There are errors of logic, of implementation, of programming, and simple quality control, These errors almost universally understate risks. Even under the conditions that the Agency purportedly models, the modeling undercalculates by orders of magnitudes the risks from FFCW. ( HEC00056)

Omissions and errors in the draft RTC which combined to overstate calculated risks for agricultural uses of coal ash by several orders of magnitude. The underlying assumptions used in this risk analysis appear to be substantially more conservative than assumptions used in previous health risk analyses performed by the EPA for other materials. EPA must maintain a consistent, objective basis in evaluating health risks for the public... The EPA health risk analysis assumed questionable values for ... arsenic cancer slope factor & reference dose. ( NSP00057)

The risk assessments are not adequate. There are several ways in which the risk assessment and exposure analyses contained in the Report are inadequate and inconsistent with Agency policy. ( 49CAO00058)

Moreover, as demonstrated in the buIk of the testimony delivered at the agency's May 21 public hearing on the Renort, these results would occur despite the fact that the agency's risk analysis seriously overstates the alleged risk from arsenic in CCPs. ( WVDEPL0003)

Choice of values for the variables in the risk equations is often difficult due to uncertainties in the distribution of these values in the environment or exposed population. " Conservative" values are often chosen in order to adequately protect the greatest proportion of the exposed population; however, when " conservative" values are used for most or all of the variables in the equation, the multiplicative effect is to generate very large cancer risk that can only represent a minute Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 5 XIV  5 percentage of the actual population exposed. This in essence represents a multiple high end scenario that is not consistent with accepted risk assessment practice. ( PHS018)

EPA's risk assessment model, which projected a remote health risk potential for arsenic through groundwater, used assumptions that we believe overstated the actual risk. ( PG& E00274)

PG& E Gen's initial comments included risk assessment criticism of EPA's model and assumptions that were used to generate the remote risk to human health for arsenic from agricultural use of FBC coal ash. PG& E Gen's review identified numerous problems that cause the model to overestimate the potential risk presented by this beneficial use of coal ash, such as ... use of unrealistic toxicity factors from a highly criticized health risk study. Other commenters to the docket have criticized EPA's risk assessment model as flawed in ways alleged to understate the actual risks presented. ( PG& E00274)

EPA's groundwater risk assessment does not under predict concentrations of metals in groundwater. As USWAG documented in its initial comments, EPA's groundwater risk analysis is based upon compound and overly conservative assumptions that over estimate risk by orders of magnitude. USWAG's initial comments, combined with the wealth of field data in the record, provide the basis for EPA to reevaluate its modeling exercise, reduce its risk estimates by orders of magnitude, and validate those results. At this time, USWAG finds it necessary to provide additional comment on EPA's risk modeling to specifically address comments filed by the Environmental Defense Fund ( EDF). Those comments allege that EPA's modeling under predicts concentrations of contaminants. However, those views are not based upon a plausible scientific foundation and do not stand up to simple field validation. ( USWAG00275)

There are significant deficiencies in each of the steps in EPA's assessment of the human health impacts of current FFC waste disposal practices. ( ALA00292)

Additionally, recent data from University of Tennessee and Wright Patterson Air Force Base's School of Engineering ( OH) show that concentrated wastes may increase health concerns outside of the water quality arena, such as radon emissions ... Again, additional data exploring all aspects of this issue need to be further examined. ( PURD00294)

We urge the agency to take this lead threat to the public health just as seriously as you have lead paint in the past. We keep hearing from the industry side about ` sound science.' Where is the soundness in a so called ` science' that would raise lead action levels by several magnitudes? ( PEACE00306) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 6 XIV  6 XIV. RISK METHODOLOGY IN GENERAL A. Response to Peer Review Comments Several commenters expressed concern that EPA had not adequately addressed peer review comments on its draft risk assessment. One of these commenters specifically referred to peer review comments about the bias in using industry provided data.

Response: EPA believes the peer review conducted for the draft risk assessment was complete and appropriate to this task. Four skilled peer reviewers were involved. Modeling methodology, with the exception of the MINTEQA2 component of EPACMTP, had been previously peer reviewed, and a request for MINTEQA2 SAB review has been received in context of the ongoing critique of EPACMTP, noted below under Topic XV. Comments about the potential bias of industry provided data are addressed under Topic XIII. B.

Peer reviewers in general requested more explicit modeling treatment of variables for which considerable uncertainty existed. This was done, as detailed in the docket, for both the groundwater and above ground pathways and in official response to comment. In some cases, key input variables were held at 3 5 times reported values, with the result that, for this one speculative change, risk changed proportionately. ( Eg 3 times 2x10 4 = 6x10 4). However, very little may be inferred from such analyses as to the likelihood of occurrence and its importance in a multivariate setting. One peer reviewer expressed concern that EPA do a more thorough ecological risk assessment, but EPA was constrained in this regard by resources and believed that resources were better spent on human health risk assessment. Aside from adjusting for the sheer volume of FFC wastes, there was little new in the risk modeling methodology for today's rulemaking. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 7 XIV  7 XIV. RISK METHODOLOGY IN GENERAL A. Response to Peer Review Comments Verbatim Commenter Statements The peer reviewers for the human health and ecological risk assessment offered a number of valuable suggestions. While a summary of the comments is included in the docket, there is no indication that comments were either used to revise the assessment or considered in the Report to Congress. ( ALA00036)

This Report is based almost entirely on data provided by industry strongly suggesting the possibility of conflict of interest. One of the Report's peer reviewers pointed out this problem, noting the potential for bias, however it is not apparent anywhere that EPA took action based on the reviewer's comment. ( 49CAO00058) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 8 XIV  8 XIV. RISK METHODOLOGY IN GENERAL B. Level of Conservatism Industry, academic, and state government commenters expressed concern that, because they combine numerous conservative ( protective) assumptions, EPA's modeling results exaggerate the degree of risk. Several of these commenters found the risk assessment for arsenic in particular to be unrealistically conservative.

In contrast, several public interest groups stated that errors in assumptions and study design resulted in gross underestimation of risk. One of these commenters stated that the assessment did not assess above average exposure conditions and risks to sensitive populations because EPA used central tendency values for all the driving parameters.

Response: Central tendency and deterministic high end analyses were performed for the risk assessment. For the central tendency risk estimation, all parameters are set to their central tendency value and the risk or hazard quotient for each constituent is calculated. The high end risk estimation uses a double high end assessment methodology, consistent with EPA Office of Solid Waste past risk assessments. With this approach, two parameters at a time are set to their high end value while the remainder of the parameters are set at central tendency, and risk values are calculated. Another combination of parameters is then set at their high end values while the remainder are set at central tendency, and this set of results is calculated. This continues until risk values are calculated for all possible high end parameter combinations. Therefore, only two variables are set to their high end values for any particular run. The above was done for all sensitive and exposed sub populations, including children in general and children of a farmer.

The FFC assessment was national in scope because the thousands of facilities with widely varying characteristics covered by the study are located throughout the country. Site specific parameter inputs values were not feasible. Given the uncertainty about characteristics of facilities and waste management units, conservative assumptions concerning parameter values are necessary to ensure protection of human health and the environment. EPA believes that the values that were used were reasonable given the high degree of variability that can be expected across the industry. The risk assessment for arsenic was no more nor less conservative than the risk assessment for all other chemicals. Comments on more specific assumptions regarding arsenic are discussed under Topics XIV. F and XVI. B.

Specific comments about exposure assumptions and sensitive populations are discussed in Section XV. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 9 XIV  9 XIV. RISK METHODOLOGY IN GENERAL B. Level of Conservatism Verbatim Commenter Statements It appears that EPA's modeling effort has created, in EPA's attempt to be conservative, an unrealistic scenario for the use of FBC ash. The extreme conservatism has resulted in the application of unreliable, mutually exclusive data that, on occasion, results in scenario parameters that break basic scientific principals. Selecting the input parameters more carefully in order to more realistically represent even extreme conditions for managed FBC ashes should dramatically change the outcome of the Report and position of the EPA on FBC ash. ( ARIPPA00019)

As discussed in this section of the comments, the groundwater modeling conducted by EPA grossly understated the risks posed by fossil fuel combustion wastes. This understatement is the result of a series of methodological flaws which individually would be significant, but when considered together, lead to profoundly invalid results. ( EDF00021)

The EPACMTP's risk assessment model significantly overestimates the risk to human health theoretically presented by potential releases from combustion ashes into the environment. The model's assumptions do not reflect the current scientific knowledge regarding the behavior of the model, using arsenic as an example, but with general applicability to other potential contaminants. Inputs to the model are overly conservative a, therefore they substantially overestimate the potential for health risk. Adual data collected by EPA and industry fail to show any evidence of harm to the environment or public health, which is confirming evidence of the overstatement of potential risk by the models. ( PG& E00023)

EPA estimates potential risks associated with fossil fuel combustion wastes throughout the Report that are based on a risk assessment for ground water pathway human health and above ground multi  pathway human health and ecological risk assessment. Both of these risk assessment models are overly conservative and likely over estimate actual risks, Therefore, the results of these risk assessments should not be used as the basis for public policy decisions with respect to risks from fossil fuel waste products. ( PG& E00023)

Therefore, the risk assessment methodology used in this risk assessment overstates the potential risks to human health or to the environment. This is futher supported by the fact that EPA has not found documentation of actual harm or significant releases of toxins such as arsenic despite considerable experience and monitoring of these practices. ( PG& E00023) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 10 XIV  10 Moreover, as demonstrated in the bulk of the testimony delivered at the agency's May 21 public hearing on the Report, these results would occur despite the fact that the agency's risk analysis seriously overstates the alleged risk from arsenic in CCPs. ( NMA00024)

Indeed, the risk assessment employed by EPA for the 1999 Renort to Congress is fatally flawed, thus greatly overstating the risk. ( NMA00024)

The assumption used in the exposure assessment and toxicity assessment could significantly underestimate the quantitative risk estimates reported by EPA. ( ALA00036)

Because the concentrations of chemicals in FFC waste are suspect, the exposure estimates are also suspect. As a result, the analysis could underestimate risks, especially to populations with above average exposures. ( ALA00036)

The exposure parameters are based on central tendency values for such factors as ingestion rates, and residence time and, therefore, do not account for above average exposures. ( ALA00036)

There are several assumptions and uncertainties in the risk assessments that could underestimate the risk estimates cited in the Report. ( ALA00036)

EPA has failed to conduct the human health risk assessment according to Agency guidelines and policies to ensure that above average exposure conditions and risks to sensitive populations are addressed. EPA used central tendency values for all the driving parameters in the risk assessments  starting waste concentration, size of unit, exposure duration, and distance to receptor. ( ALA00036)

By using extremely conservative assumptions in the model that fail to mimic real world conditions, the model produces exaggerated risk conclusions divorced from reality and ceases to be a tool for sound regulatory decision making. ( USWAG00037)

To the extent that EPA has based recommendations against further regulatory action on the risk assessment results, those recommendations are sound because the modeling skewed the analysis towards overly conservative predictions and the Agency quite properly discounted the inflated risk numbers. However, in the few instances where EPA relied on the risk assessment to justify consideration of additional regulation, the flawed assumptions and analysis fatally undermine the risk assessment as a tool for regulatory decisionmaking. ( USWAG00037)

Not only did EPA neglect the wealth of real world data in favor of a model that is ill equipped to simulate the conditions occurring in FFC waste landfills and surface impoundments, but the Agency modeled conditions that are too far removed from reality to form a defensible foundation for regulatory action. Conservative assumptions may well have their place in policymaking where Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 11 XIV  11 there is irreconcilable. But, where uncertainty can be reduced by reference to observational data, such conservative assumptions no longer are justified. Furthermore, the compound effect of numerous simultaneous conservative assumptions must be avoided if the modeling results are to have any basis in reality. In both the groundwater and non groundwater pathway risk assessments, EPA selected overly conservative assumptions for numerous key parameters, compounding errors by orders of magnitude. The results of that effort show that arsenic risk potential exceeds conservative protective levels by two orders of magnitude in the worst case scenario. Those results are merely noise generated by the extremely conservative assumptions and are indefensible. ( USWAG00037)

The modeling incorporated numerous overly conservative and technically inappropriate assumptions including the questionable application of pore water data. ( APSC00043)

The risk assessment that models the fate and transport of contaminants in ground water dramatically and falsely understates the real risks that are occurring from disposal of fossil fuel wastes. The methodology used in the risk assessment that is based on EPACMTP modeling, is fundamentally flawed. There are errors of logic, of implementation, of programming, and simple quality control, These errors almost universally understate risks. Even under the conditions that the Agency purportedly models, the modeling undercalculates by orders of magnitudes the risks from FFCW. ( HEC00056)

Omissions and errors in the draft RTC which combined to overstate calculated risks for agricultural uses of coal ash by several orders of magnitude. The underlying assumptions used in this risk analysis appear to be substantially more conservative than assumptions used in previous health risk analyses performed by the EPA for other materials. EPA must maintain a consistent, objective basis in evaluating health risks for the public. ( NSP00057)

The exposure and risk assessments seemingly do not represent a " high end" analysis, but rather represent averaged data. ( 49CA00058).

Moreover, as demonstrated in the buIk of the testimony delivered at the agency's May 21 public hearing on the Renort, these results would occur despite the fact that the agency's risk analysis seriously overstates the alleged risk from arsenic in CCPs. ( WVDEPL0003)

Choice of values for the variables in the risk equations is often difficult due to uncertainties in the distribution of these values in the environment or exposed population. " Conservative" values are often chosen in order to adequately protect the greatest proportion of the exposed population; however, when " conservative" values are used for most or all of the variables in the equation, the multiplicative effect is to generate very large cancer risk that can only represent a minute percentage of the actual population exposed. This in essence represents a multiple high end scenario that is not consistent with accepted risk assessment practice. ( PHS018) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 12 XIV  12 EPA's risk assessment model, which projected a remote health risk potential for arsenic through groundwater, used assumptions that we believe overstated the actual risk. ( PG& E00274)

PG& E Gen's initial comments included risk assessment criticism of EPA's model and assumptions that were used to generate the remote risk to human health for arsenic from agricultural use of FBC coal ash. PG& E Gen's review identified numerous problems that cause the model to overestimate the potential risk presented by this beneficial use of coal ash. ( PG& E00274)

EPA's groundwater risk assessment does not under predict concentrations of metals in groundwater. As USWAG documented in its initial comments, EPA's groundwater risk analysis is based upon compound and overly conservative assumptions that over estimate risk by orders of magnitude. USWAG's initial comments, combined with the wealth of field data in the record, provide the basis for EPA to reevaluate its modeling exercise, reduce its risk estimates by orders of magnitude, and validate those results. At this time, USWAG finds it necessary to provide additional comment on EPA's risk modeling to specifically address comments filed by the Environmental Defense Fund ( EDF). Those comments allege that EPA's modeling under predicts concentrations of contaminants. However, those views are not based upon a plausible scientific foundation and do not stand up to simple field validation. ( USWAG00275)

EPA used numerous assumptions in the risk assessment that are overly conservative and conflict with scientific research. ( USWAG00275)

The Report's use of questionable waste characterization data ( which are at the heart of any analysis of whether or not to regulate as a hazardous waste) suggests that EPA's quantification of human health risks associated with exposure to groundwater contaminated with FFC waste is uncertain and likely underestimated. ( ALA00292)

There are significant deficiencies in each of the steps in EPA's assessment of the human health impacts of current FFC waste disposal practices. The cumulative effect of these deficiencies indicates that EPA has underestimated the human health impacts associated with exposure to FFC wastes, particularly to individuals with above average exposures. ( ALA00292)

Based on a comparison of the values used by EPA in the ground water risk assessment and the values representing the 90th percentile for the U. S. population, it is apparent that EPA has not evaluated the high end reasonable exposures. ( ALA00292) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 22 see FF2P S0363 for documentation of these results.

13 XIV  13 XIV. RISK METHODOLOGY IN GENERAL C. Constituents Considered Several public interest group and academic commenters expressed concern that EPA did not consider specific constituents in the risk assessment or questioned the methodology used to characterize and assess certain constituents. Several commenters expressed concern that EPA did not consider mercury in the risk assessment.

Other specific constituents about which the commenters expressed concern are identified in the numbered items below, with specific responses to each concern.

Response: The data provided to EPA contained only inorganics. The risk assessment did not initially consider secondary parameters ( i. e., parameters for which only secondary MCL's exist) because these parameters are of concern mainly for non human health ground water impacts ( e. g., taste, smell, appearance). Exceedences of secondary MCL's have not been the basis for regulatory action in the past. Nonetheless, EPA recognizes the potential importance of such measures both in long term ground water quality and as possible precursors to metals mobility. The issue of observed exceedences of secondary MCL's is discussed further under Topic XIX. D and was taken into consideration for today's rulemaking. No evidence of radionuclides was provided to EPA. ( The question concerning the presence of radionuclides is also address in Section XIII F.)

The initial ground water risk assessment did consider mercury and found that mercury concentrations were below levels of concern. 22 Subsequently, EPA conducted additional analysis of risks from mercury using a more protective ( i. e., erring on the side of safety) assumption about the speciation of mercury ( i. e., assuming all mercury present was in the more toxic methyl mercury form). No hazard quotients in excess of 1 were found.

Below are the specific constituent related comments and responses.

1. One of the commenters expressed concern about eight metals for which the commenter believed industry data included only non detect levels. The commenter was uncertain how ( or whether) input concentrations were calculated for these metals.

Response: The commenter's concern about industry data including only values below detection limits for eight metals appears to be based on a misinterpretation of docket materials. In a memorandum regarding EPA's validation sampling in conjunction with industry sampling efforts Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 23 FF2P S0092.

14 XIV  14 at three sites, 23 it was observed that approximately eight metals per sample were reported below detection limits in the industry data. This observation applies only for the three sites discussed in the memorandum and the specific metals found below detection limits varied from sample to sample. Therefore, for most metals, EPA was able to calculate input values from a distribution of samples that included both detected and non detect values. Furthermore, EPA incorporated the non detected values in the calculation by substituting ½ the reported detection limit. The only exceptions were antimony, beryllium, and silver in comanaged wastes. Antimony and silver were not present above detection limits in any comanaged waste pore water sample and beryllium was present above detection limits in only one of 11 samples. Given the low frequency of detection for these three metals in comanaged waste, EPA does not believe they are present at levels of concern and did not include them in the risk assessment modeling. EPA acknowledges some concern with the comparitive results of different labs and if groundwater modeling is re visited will address thi. s 2. One commenter was concerned that EPA did not evaluate certain metals for which adsorption isotherms were unavailable in the ground water model.

EPA acknowledges that there are several constituents ( boron, fluoride, manganese, molybdenum, nitrate, nitrite, and strontium) detected in FFC wastes for which the ground water model does not include adsorption isotherms. Based on the Agency's screening analysis, however, none of these constituents exceeded HBLs for OCWs and only manganese and molybdenum exceeded HBLs for FBC wastes. Screening hazard quotients ( HQs) for manganese and molybdenum in FBC wastes were 1.51 and 2.80, respectively, meaning only limited dilution and attenuation in the environment would be required to reduce these constituents below levels of concern. Therefore, the Agency does not believe any of these constituents would be of concern for the oil and FBC sectors.

In comanaged coal combustion wastes, the screening analysis showed that all of the unmodeled constituents except strontium would exceed HBLs, with screening HQs ranging from 14.3 to 133. Dilution and attenuation factors calculated for other, modeled constituents in comanaged coal combustion wastes ranged from 1.77 to greater than 1019. Therefore, it is possible, although not certain, that some of the unmodeled constituents could have continued to exceed HBLs in a high end deterministic scenario for comanaged coal combustion wastes, had modeling been possible. The Agency notes, however, that, even had some of the unmodeled constituents exceeded HBLs after modeling, none of the constituents are among those that make up the toxicity characteristic for hazardous wastes. Nevertheless, EPA is conducting a broad review of the ground water model. If, in the course of this review, it is determined that development of adsorption isotherms for these constituents is possible, given the state of science, and warranted, the Agency may revisit its conclusions regarding these constituents. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 24 FF2P S0370. Non groundwater Pathways, Human Health and Ecological Risk Analysis for Fossil Fuel Combustion Phase 2 ( FFC2). Draft Final Report. RTI. June 5, 1999.

15 XIV  15 3. One commenter pointed to the use of a technology based action level for lead in the ground water assessment, while the non groundwater risk assessment did not evaluate lead because it does not have toxicity benchmarks. Another public interest group commenter was concerned that EPA did not seriously consider risks from lead.

Response: EPA's risk assessment considered lead. Because lead does not have human health toxicity benchmarks ( i. e., RfC, RfD, CSF), risks or hazard quotients cannot be calculated. However, lead does have the potential for adverse health and developmental effects, especially for children. To estimate the potential for adverse effects from lead, the ground water risk assessment uses the so called action level ( 400 mg/ kg) for lead as the best available benchmark for drinking water ingestion. Lead concentrations at receptor wells, using available data and the current ground water model, were below action levels. Table 3 ( which was originally presented as Table 5 18 on page 46 of the non groundwater risk assessment technical background document24) presents the maximum lead soil concentrations that were calculated for each scenario modeled. All lead soil concentrations fall well below 400 mg/ kg. The Agency, therefore, concluded that lead levels resulting from the management of FFC wastes are unlikely to cause a significant threat to human health.

Table 3. Maximum Estimated Lead Concentrations in Soil Per Scenario Scenario Lead Soil Concentration ( mg/ kg)

Utility Coal fired Comanaged Waste Onsite Landfill 7.63 Utility Coal fired Comanaged Waste Dewatered Surface Impoundment 1.30 Utility Oil fired Waste Onsite Landfill 0.98 FBC Onsite Landfill 0.81 FBC Used as Soil Amendment 0.009 Non utility Coal fired Waste Onsite Landfill 0.21 Non utility Coal fired Waste Offsite Landfill 1.33 Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 16 XIV  16 XIV. RISK METHODOLOGY IN GENERAL C. Constituents Considered Verbatim Commenter Statements Despite the conclusion that mercury is " screened out' of the analysis based on TCLP results, the concentrations measured ( even when the median values are taken) reveal that nationally, tons of mercury are being mobilized in these waste disposal sites. The lack of consideration given to mercury releases runs counter to the Administrator's PBT strategy. ( ALA00036)

There is inconsistency between the dose response assessment used in the groundwater and nongroundwater risk assessment. For example, the hazard benchmark level for lead in groundwater is a technology based action level. The peer review comments by Dr. James Butler ( 1998) noted that " a technology based interim standard is not the most appropriate value to use as a benchmark value ( especially for evaluating risks to children)" In the non groundwater risk assessment, lead was not evaluated " because lead does not have human health toxicity benchmarks risks or hazard quotients cannot be calculated." ( ALA00036)

The risk assessments do not model or even consider the potential for serious damages from constituents in these wastes other than from a select group of metals. Constituents in coal ash that have caused such damage include sulfates, boron, TDS, sodium, chlorides, fluorides and pH. In many cases these constituents have made potable ground waters well offsite virtually unusable. ( HEC00056)

The potential for harm from greater amounts of nitrogen compounds in fluidized boiler wastes is not addressed. ( HEC00056)

The human health risks of non groundwater exposure to mercury were not modeled, even though mercury is an acknowledged constituent of co managed FFC wastes, and a toxic chemical that is a priority pollutant for EPA. ( ALA00292)

Furthermore, with regards to the duplicate samples that were analyzed by the Independent laboratory, the EPRI contractor lab had detection limits for 8 metals that were between 25 and 10,000 times higher than the independent lab. ( This discrepancy cannot be explained, as both labs used identical procedures). The result of this is that the EPRI contractor reported non detectable concentrations for the eight metals, compared to positive concentrations reported by the independent lab. In the waste characterization, these non detects were treated as one half the detection limit, however in cases where most of the samples did not have detectable levels, no statistical analyses were performed ( i. e.. mean median and various percentiles). If the statistical analyses were not available then it is unclear whether these constituents were included in the risk assessments or whether they were dropped. If these constituents were included, it is unclear what Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 17 XIV  17 the input values would be because the 50th and 95th percentile values were not calculated. ( ALA00292)

In addition to uncertainties associated with quantifying the concentration of inorganic FFC waste constituents discussed above, EPA eliminated the organic and radioactive constituents in FFC waste from the risk assessment without any justification. This is despite the fact that these potentially toxic organic constituents, including dioxins and furans, were detected in the samples from site investigations, as reported in the Background Technical Support Document on Waste Characterization ( page2 13). ( ALA00292)

EPA did not evaluate certain metals because of lack of data on adsorption isotherms that describe the tendency of metals to remain bound to particle surfaces. ( ALA00292)

Additionally, recent data from University of Tennessee and Wright Patterson Air Force Base's School of Engineering ( OH) show that concentrated wastes may increase health concerns outside of the water quality arena, such as radon emissions. Minute traces of K 40, Th 232, U 238, and Rn 222, present naturally in the soil, are concentrated through coal combustion to levels of concern. Studies at Wright Patterson calculated that the indoor radon concentrations in a structure built near such a CCW site would be 11.48 pCi/ l, well above the EPA's action level of 4.0 pCi/ l. In Indiana, where disposal sites need not be located and recorded, this opens the possibility of health issues not related to water quality should residential sites be located in abandoned coal fields. Again, additional data exploring all aspects of this issue need to be further examined. ( PURD00294)

We urge the agency to take this lead threat to the public health just as seriously as you have lead paint in the past. We keep hearing from the industry side about ` sound science.' Where is the soundness in a so called ` science' that would raise lead action levels by several magnitudes? ( PEACE00306) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 18 XIV  18 XIV. RISK METHODOLOGY IN GENERAL D. Methodology for Considering Child Risks One public interest group commenter questioned why specific models ( e. g., guidance on the evaluation of lead exposure in children by the Integrated Exposure Uptake Biokinetic ( IEUBK) model; the multi pathway risk assessment ( MPRA) model) were not used to assess child risks.

Response: Based on the analysis for lead that is discussed under Topic XIV. C, that showed lead levels well below the appropriate benchmarks, it was decided that assessing child lead exposures with IEUBK was not necessary. Risks to children were explicitly considered by varying all risk parameters in all pathways of special relevance to children. These included ingestion rates, inhalation rates, body weights, exposures times, et al. Where risks to children were found at actionable levels, and where these differed to any significant degree from risks to adults, they are noted in all documents. The MPRA model was not available in time for this regulatory determination action. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 19 XIV  19 XIV. RISK METHODOLOGY IN GENERAL D. Methodology for Considering Child Risks Verbatim Commenter Statements Both these assessments overlook guidance established by EPA on the evaluation of lead exposure in children. " The Integrated Exposure Uptake Biokinetic ( IEUBK) is a menu driven, user friendly model designed to determine exposure from lead in air, water, soil, dust, diet, paint, and other sources. Pharmacokinetic modeling is used to predict blood lead levels in children 6 months to 7 years of age. The four main components of the current IEUBK model are: ( 1) an exposure model that relates environmental lead concentrations to age dependent intake of lead into the gastrointestinal tract; ( 2) an absorption model that relates lead intake into the gastrointestinal tract and lead uptake into the blood; ( 3) a biokinetic model that relates lead uptake in the blood to the concentrations of lead in several organ and tissue compartments; and ( 4) a model for uncertainty in exposure and for population variability in absorption and biokinetics. This model is used in conjunction with the Guidance Manual and other supporting documentation by several EPA offices. ( ALA00036)

In the EPA's Children's Environmental Health Yearbook ( EPA 100 S 98 002, June .1998, page 125), it is stated that " EPA requires that assessments of children's risk include the use of Agency methods for assessing risk specifically to children ( e. g., Guidance Manual for the Integrated Exposure Uptake Biokinetic Model for Children). No mention or use of this model is made in the Report. Also in the Yearbook ( page 126), there is a section on Office of Solid Waste ( OSW) Risk Assessments. It reads: " EPA continues to include children when considering risks posed by contaminants. A new multi pathway risk assessment ( MPRA) model evaluates human and ecological risks from the disposal of nlorc than 100 waste constituents ( 50 evaluated for ecological risk). The MPRA evaluates the movement of contaminants through the air, surface water, groundwater and soil and the chemical changes that occur during this movement. Because of their small body weight and lifestyle, children may be more likely to encounter higher exposures per unit bo< iy weight than adults. In addition, children are more sensitive to certain toxics such as lead and mercury." Given that OSW prepared the FFC report, why is no mention or use of this model in the risk assessment? ( ALA00036) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 20 XIV  20 XIV. RISK METHODOLOGY IN GENERAL E. Selection of Benchmarks ( HBL versus MCL)

Industry commenters and a single public interest group commenter believed EPA should use MCLs as benchmark values for the risk assessment and calculate HBLs only when MCLs are not available. The industry commenters also disagreed specifically with using the HBL for arsenic because it is below detection limits or below background levels of arsenic. The public interest group commenter also stated that the HBLs were based on inappropriate toxicity values.

Response: EPA agrees that MCLs should be one of the values to be considered in its risk assessment, and for this reason compared arsenic levels against the current MCL and a range of potential MCLs. ( See Topic XIV. F following.) However, in the RCRA program EPA uses HBLs as the primary consideration in its risk assessments because HBLs represent health effects of the contaminant using the most current toxicity and exposure assumption information available. Also, HBLs are not influenced by technical and economic factors. Thus EPA used both MCLs and HBLs.

The arsenic MCL, as is noted in XIV. F below, is now under careful review in the scientific community. EPA's comparision of leachate, sampling and receptor well concentrations to arsenic MCLs was begun on the October groundwater 1998 report, and subsequent comparisons found that arsenic concentrations have the potential to exceed various plausible arsenic MCLs ( as well as the HBL) for comanaged impoundments and landfills, and FBC management units.

Thus, EPA recognizes and took account of the possibility that the arsenic MCL, now under review, is likely to change when EPAs Office of Water publishes a revised MCL ( now due under court order by January 1, 2001.)

EPA does not dispute the commenter's assertion that the resulting HBL for arsenic may be within the range of background concentrations ( at certain sites) or below detection limits. EPA's modeling, however, is based on incremental risk, above background, and the modeled source terms were based on reported concentrations of arsenic. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 21 XIV  21 XIV. RISK METHODOLOGY IN GENERAL E. Selection of Benchmarks ( HBL versus MCL) Verbatim Commenter Statements The derivation of a health based number for arsenic was unnecessary given that EPA has already established 0.05 mg/ L. as the drinking water standard. ( PG& E00023)

The absence of toxicological profiles for health based criteria used to estimate risks of FFC waste prevents any opportunity to comment on this critical risk assessment component. Briefly, it is apparent that the hazard benchmark Ievels used in the Report were based on average exposure parameters and inappropriate toxicity values. ( ALA00036)

EPA inappropriately calculated HBLs where MCLs are available. EPA unnecessarily calculated a benchmark value for arsenic ( 0.00029 mg/ L) that is two orders of magnitude lower than the MCL value ( 0.05 mg/ L). Furthermore, the benchmark value is not detectable. In contrast, the benchmark values derived for the other metals are larger than the MCL. EPA should use MCLs for all constituents where MCLs are available and use calculated HBLs only when MCLs are not available. ( USWAG00037)

HBNs are not protective of public health ... As discussed in the initial comments made to the docket, EPA did not provide toxicological profiles to evaluate the dose response values used to calculate the hazard benchmark numbers ( HBNs). The most serious concern regarding the doseresponse assessment conducted in the groundwater risk assessment is the considerable differences between the Hazard Benchmark Numbers ( HBNs) and maximum contaminant levels or MCLs ... The MCLs listed in Table 5 are primary legally enforceable standards that apply to drinking water systems. Primary standards are intended to protect drinking water quallty by limiting the levels of a specific contaminant that can adversely affect public health. Since state regulations can be no less stringent than the federal MCLs, action would be taken to address the potential public health hazards from FFC waste contamination in drinking water at much lower levels than HBNs suggest. Furthermore, comparisons of peak concentrations of selected FFC waste constituents that were provided in the June 25th memo from SAIC are presented in Table 6. These comparison indicate that the 95th percentile concentration  which we believe are likely underestimated  exceed primary MCLs, and, therefore, constitute potential public health risks. ( ALA00292) Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 22 XIV  22 XIV. RISK METHODOLOGY IN GENERAL F. Arsenic Toxicity Several industry and academic commenters suggested that EPA used an inappropriate cancer slope factor ( CSF) for arsenic ( based on a study that overpredicts cancer risk for U. S. populations) and/ or misapplied this CSF in its risk assessment, particularly for child risks, resulting in an overestimate of risk. According to some of these commenters, the resulting arsenic RfD should have been 0.0008 mg/ kg/ day rather than 0.0003 mg/ kg/ day. Other industry commenters stated that we evolved as a species in an environment that contains arsenic and, therefore, small incremental exposure are extremely difficult to monitor and the risks associated with that exposure become even more problematic to assign and evaluate. A public interest group commenter, however, stated that if EPA were to apply the reanalysis of epidemiological data regarding the carcinogenicity of arsenic by the National Research Council, the potency of arsenic may increase by ten times. This commenter further stated that analysis underway at EPA's Office of Water suggests the arsenic CSF is likely to be revised downwards in the future, increasing arsenic's estimated toxicity.

Response: EPA recognizes that the CSF for arsenic has been debated for several years and acknowledges the uncertainties associated with the risk assessment. The recent National Research Council ( NRC) study (" Arsenic in Drinking Water", National Research Council, National Academy Press, 1999) suggesting a lower drinking water MCL has heightened our concern with regard to the potential presence of arsenic. EPA's Office of Water ( OW) is now considering reducing the MCL as recommended by the NRC study, and is charged with finalizing an MCL for arsenic by January 1, 2001. It was because of this uncertainty that EPA compared contaminant concentrations to a postulated range of possible MCLs, as well as the HBL, in its risk characterization.

The ongoing debate as to the appropriate drinking water MCL is part of a much larger arsenic debate involving possible cancer types ( including skin, bladder and lung) and incidence as a function of genetics, sex, nutrition and other factors. Bioavailability as a function of arsenic speciation and associated mobility is another complicating factor, especially where, as in this FFC analysis, no speciation data were available. Another factor making any arsenic risk characterization difficult is continuing uncertainty concerning low dose extrapolation. The NRC study concluded that the dose response curve might exhibit sublinear characteristics in the low dose region, but went on to qualify this by stating that there was no assurance that a departure from linearity was yet justified. Justification for reducing the MCL is thus based on weight of evidence as set forth in the NRC report rather than on resolution of low dose response issues.

The current CSF, contained in EPA's IRIS data base, was based on skin cancer effects alone and did not other cancers now considered to pose potential risk. A revised risk characterization will be conducted to support any new CSF. Until the arsenic risk characterization is updated, the current CSF in IRIS remains as the recommended value. While the implication of Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 23 XIV  23 the NRC study is that a new CSF is justified, the NRC study did not make a specific recommendation in this regard.

For non carcinogenic effects, IRIS lists an RfD of 0.0003 mg/ kg/ day for inorganic arsenic. IRIS notes that valid arguments can be made that would increase or decrease the RfD by a factor of perhaps 2 or 3, resulting in a possible range of 0.0001 to 0.0008 mg/ kg/ day. Using an RfD of 0.0008 mg/ kg/ day instead of 0.0003 mg/ kg/ day, however, would have little effect on the outcome of the risk assessment. In addition, RfD methodology is considered to embody values with uncertainty spanning at least an order of magnitude. Furthermore, risk estimates identified for arsenic were based on cancer effects, which is independent of the RfD. ( It is not correct, as stated in several of the comments, that the CSF is used to derive the RfD.

See Section VIII for additional discussion of this issue. Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 24 XIV  24 XIV. RISK METHODOLOGY IN GENERAL F. Arsenic Toxicity Verbatim Commenter Statements There seems to be some concern with regard to the actual assumptions that went into assigning the toxicity to arsenic that clearly needs to be evaluated. Arsenic fails in all cases because of the larger risk that EPA has associated with it. For example, the biota in which we have evolved in has developed in a sea of radioactivity. We are what and who we are because of the environment, including the radioactive background. If small incremental increases to radioactive exposures occur, our ability to quantify the impact of this event is very limited. Modeling exposure consequences for high dose events and extrapolating through these events is straightforward. However, extrapolating to the background exposure becomes very tricky. Our exposure to arsenic follows exactly the same scenario. We evolved as a species in an environment that contains arsenic ( see Appendices II and III). Small incremental exposures are extremely difficult to monitor and the risks associated with that exposure become even more problematic to assign and evaluate. ( ARIPPA00019)

EPA's approach in establishing a health based number of 0.00029 mg/ l, a value which is greater than 200 times less than EPA's current standard, was overly conservative based upon current human health population statistics, published background conditions throughout the united states and toxicity factors critiqued by EPA. Health based numbers were calculated using toxicological information, ingestion rate, frequency, duration, and receptor body weight based on current acceptable population statistics. EPA's assumption that human health population statistics will not evolve at all over the next 400 years is highly speculative. Changes in human diet, living conditions, and medical advances alone in the past 400 years demonstrate how speculative this assumption is. The literature background concentrations for arsenic in natural groundwater range from 0.00 1 to 0.03 mg/ l ( Dragun, 1988). Background concentrations of arsenic in the absence of any fossil fuel combustion waste are typically 3.4 to 100 times greater than the health based number used by EPA in the Report ( 0.00029 mg/ l). Again, this results in overly conservative assumptions and conclusions that are not based on real world conditions. The toxicity factors used to calculate a health based number for Arsenic are based on the prevalence of normally nonfatal skin cancer observed in a Taiwan epidemiological study conducted by Tseng et al. This study has been peer reviewed and has been shown to have study limitations that likely over predict actual cancer risks for US populations. The results of this study likely over predict actual cancer risks for U. S. populations. That this modeling seriously overstates the potential risks to human health or to the environment is supported by the fact that EPA has not found documentation of actual harm or significant releases of toxins such as arsenic despite considerable experience and monitoring of these practices. ( PG& E00023)

As discussed previously ( Section C. 2) the toxicity factors used to calculate a Heath based number for arsenic are inappropriate and have been questioned by EPA and other health scientists. The Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 25 XIV  25 toxicity factors are based on the prevalence of normally non fatal skin cancer observed in a Taiwan epidemiological study conducted by Tseng et al. This study has been peer reviewed and has been shown to have study limitations that likely over predict actual cancer risks for US populations. ( PG& E00023)

The risk assessment should not have utilized data from the Taiwan arsenic epidemiological studies, since those studies have major flaws that " invalidate the use of these data for most exposed individuals in the US". ( NMA00024)

Arsenic is consistently identified in each of the waste management scenarios at levels of public health concern. If we were to apply the recent reanalysis of epidemiological data regarding the carcinogenicity of arsenic by the National Research Council, the potency of arsenic may increase by ten times. This would increase the highest risks reported for arsenic from groundwater contamination by coal waste from one in one hundred to one in ten. ( ALA00036)

The cancer slope factor used to derive the reference dose ( RfD) of 0.0003 mg/ kg/ day used in the nongroundwater risk asseT; ment is based upon a fundamentally flawed epidemiological study. In the 40 C. F. R. Part 503 Subpart B biosolids rulemaking, EPA used a reasonable RfD value of 0.0008 mg/ kg/ day. If the biosolids risk assessment had used an RfD value of 0.00CB2mg/ kg/ day, it would return an acceptable limit for As of only 1 ppm. To put the absurdity of that result in context, note that the U. S. Geological Survey has reported a nationwide mean soil background As concentration of 5.2 ppm with a standard deviation of 2.23 ppm. ( USWAG00037)

Testimony presented by Dr. Chaney or the USDA at the EPA Public Hearing on May 21, 1999, highlighted serious flaws in the determination of the arsenic cancer slope factor used for justifying the arsenic reference dose of 0.0003 mg/ kg/ day. In this RTC health risk analysis, results indicate that potential health risks from children ingesting soil with a arsenic concentration of 1 ppm. If this is indeed the case, we need to enact national regulations against any child eating any native soil, as the USGS has determined that the average soil in the United States contains over 5 times the " safe" concentration of arsenic! ( Refer to USGS Professional Paper 1270.) Previous EPA health risk analyses, notably for land application of sewage sludge ( 40 CFR 503( b) Rules), used an arsenic reference dose of 0.0008 mg/ kg/ day, resulting in a more realistic " safe" arsenic concentration of 41 ppm. ( NSP00057)

Cancer Slope Factor ( CSF): EPA determines this value from reviews of the available toxicological literature; prior to about 1997 an oral dose of 0.0008 mg/ kg d As was considered acceptable, but this was subsequently reduced to 0.0003 mg/ kg d. EPA acknowledges considerable uncertainty in this value ( see comments in IRIS database, U. S. EPA), and states that this uncertainty gives environmental managers " considerable flexibility" in assessing risk for a given scenario. The CSF factor of 1.5 is based on limited data, and is likely to be on the Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 26 XIV  26 conservative side. However, given the lack of further information it is difficult to treat this value as an " adjustable" parameter in the risk assessment. ( PHS018)

Errors in Taiwan epidemiological study prevent it use in risk assessment. During consideration of changes in the As limit for drinking water, EPA was informed that the major Taiwan epidemiological study by Tseng et al. was seriously flawed during data collection. Individuals in the same village had high As and very low As well water, and drank the water from their own well during their life. Nevertheless, it has been found that the median well As concentration was used to classify the village As exposure when assessing cancer outcomes may decades later. Further, errors were found in the method of analysis of As in water at lower concentrations. Together these errors cannot be corrected since the low response of persons with low exposure cannot be separated reliably from the overall data. EPA should not be using the cancer slope factor based on that work in development of risk assessments, regulations, or Reports to Congress, nor a RfD which is based on this cancer slop factor. ( PHS011)

Water consumption by the exposed Taiwanese population is greater than the 2 L/ day assumed by EPA in risk assessment, which increased the cancer slope factor inappropriately. During the drinking water As risk assessment, the volume of water required by persons working outdoors in sunny rice fields in the summer in Taiwan became a subject of debate. With recent experience within DOD of water requirements of persons in such hot climates, EPA was advised to shift to 8 L water per day rather than 2 L/ day assumed in US risk assessments. This change would reduce the cancer slope factor by about 4 fold. ( PHS011)

Inorganic As in rice contributed significantly to As exposure in the Taiwanese exposed population, which increased the cancer slope factor inappropriately. Research by Schoof et al. ( 1998) and Yost et al. ( 1998) identified a separate error in the As dose estimation for the Taiwan population. It had been assumed by EPA's Office of Drinking Water that most As in plants was organic. Measurement of the species of As in rice and dried yams, principle foods of the exposed farm populations in Taiwan, showed these foods to contain largely inorganic As. This As would have added to the inorganic As dose; with constant measured response, the cancer slope factor would have been found to be lower. ( PHS011)

Research has shown that the extent of harm to the Taiwanese and other As harmed populations was partially related to poor nutrition of this population during their exposure. Although there is no clear way to deal with the effect of malnutrition in risk assessment for US populations other than consideration of " High End" exposures, evidence from many locations where humans have suffered skin disease from excessive long term consumption of As rich drinking water has indicated that persons with the same water, but better diets, did not suffer evident skin lesions. Some evidence suggested the main difference might be the intake of meats with more methyl donor amino acids, etc., which might have increased the rate of As detoxification by persons with improved nutritional status. Because exposed US populations are not so severely malnourished as the subsistence rice consuming populations in Asia, it may be appropriate to reconsider the dose Comment Summary and Response Document Report to Congress: Wastes from the Combustion of Fossil Fuels April 2000 27 XIV  27 response relationship estimated for the Asian populations. When safety factors are hidden in risk assessment, unnecessary concerns are raised. ( PHS011)

PG& E Gen's review identified numerous problems that cause the model to overestimate the potential risk presented by this beneficial use of coal ash, such as ... use of unrealistic toxicity factors from a highly criticized health risk study. ( PG& E00274)