What Are the Environmental and Health Eff ects Associated with Disposing of CCRs in Landfills and Surface Impoundments?

EPA has evaluated potential human and ecol ogical risks from exposure to CCR chemical constituents for more than twenty years. Th e following section summarizes the our work, from the mid-1990s until the present and includes desc riptions of damage cases found and risk assessment work conducted to identify the most lik ely combinations of chemical constituents and organisms that may be at risk. EPA’s risk asse ssment work includes four analyses: 1) U.S. EPA 1998, “Draft Final Report: Non-groundwater Path ways, Human Health and Ecological Risk Analysis for Fossil Fuel Combustion Phase 2 (FFC2) ” (June 5, 1998) referred to hereafter as the 1998 Non-groundwater risk assessment (available in docket # F-1999-FF2P-FFFFF in the RCRA Information Center, and on the EPA website at http://www.epa.gov/osw/nonhaz/industrial/spe cial/fossil/ngwrsk1.pdf); 2) preliminary groundwater and ecological risk screening of selected constituen ts in U.S. EPA 2002, “Constituent Screening for Coal Combustion Wast es,” (contractor deliverable dated October 2002, available in docket EPA-HQ-RCRA-2006- 0796 as Document # EPA-HQ-RCRA-2006- 0796-0470); referred to hereafter as the 2002 scr eening analysis; 3) U.S. EPA 2009a, “Human and Ecological Risk Assessment of Coal Combus tion Wastes” (September 2009) available in the docket for this proposed rule, and referred to he reafter as the 2009 risk assessment; and 4) U.S. EPA 2009b, “Inhalation of Fugitive Dust: A Screen ing Assessment of the Risks Posed by Coal Combustion Waste Landfills” available in the docket for this proposed rule.

Human Health RisksIndividuals can be exposed to the constituents of concern found in CCRs through a number of exposure routes. Potential contaminant rel eases from landfills a nd surface impoundments include: leaching to ground water; overland transport from erosion and runoff; and air emissions. The potential of exposure from any one of these exposure pathways for a particular chemical is dependent on the physical and chemical characte ristics of the chemical , the properties of the waste stream, and the environmental setti ng. EPA has conducted a peer-reviewed risk assessment of potential human health risks from CCR constituents leachi ng to groundwater that subsequently migrate either to a nearby drinking water well, or to nearby surface water, and is ingested as drinking water or through fish consumption (U.S. EPA 2009a). EPA has also performed preliminary analyses of human health effects from constituents that have eroded or have run off from waste management units (U.S . EPA 2002), and of human health effects from breathing windblown particulate matter from landfill disposal operations (the 1998 risk assessment and U.S. EPA 2009b).

Longstanding EPA policy is for EPA risk assessment s to include a characterization of the risks at two points on a distribution, or range, of risk estimates: a central tendency estimate that represents conditions likely to be encountered in a typical ex posure situation, and a high end estimate that represents conditions likely to be encountered by i ndividuals with higher exposures (U.S. EPA 1995). 1 Examples of factors that would infl uence a nearby resident’s exposure are

1 Guidance for Risk Characterization , U.S. Environmental Protectio n Agency, 1995; accessible at http://www.epa.gov/OSA/spc/pdfs/rcguide .pdf, which states that “For the Agency's purposes, high end risk descriptors are plausible estimates of the individual risk for those persons at the upper end of the risk distribution,” or conceptually, individuals with “exposure above about the 90th percentile of the population distribution”). Asthe residence’s distance from a CCR waste mana gement unit, and an individual’s behavior or activity patterns. In the 2009 risk assessment, the high e nd risk estimates are the 90 th percentile estimates from a probabilistic analysis.

The comparisons that EPA uses to judge whether either a high end or central tendency estimated risk is of concern are the risk criteria. For an in dividual’s cancer risk, the risk criteria are in the range of 1 x 10 -6 , or one in one million “excess” (above and beyond pre-existing risk) probability of developing cancer during a lifetime, to 1 x 10 -4 (one in ten thousand), 2 with 1 x 10 -5 (one in one hundred thousand) being the “p oint of departure” for listi ng a waste as hazardous. For human non-cancer hazard, the risk criterion is an estimated exposure above the level at which no adverse health effects would be expected to occur (expr essed as a ratio of the estimated exposure to the exposure at which it is likely that there woul d be no adverse health eff ects; this ratio is also called a hazard quotient (HQ), and a risk of conc ern equates to a hazard quotient greater than one), or, in certain cases of drinking water exposure, water concentrations above the MCL established under the Safe Drinking Water Act.

The exposure pathways for humans that EPA has evaluated for CCR landfills and surface impoundments are nearby reside nts’ groundwater ingestion an d air inhalation, and fish consumption by recreational fishers:

Ground Water Ingestion
suggested in the Guidance , we also provide 50th percentile results as the central tendency estimate of that risk distribution.

2 See 40 CFR 300.430.Contaminants can leach from CCRs in landf ills and surface impoundment s into the groundwater and subsequently be ingested by individuals w ho use groundwater as a s ource of drinking water. A detailed discussion of the modeling and risks from this pathway can be found in U.S. EPA 2009a (available in the docket for this proposal). This report presents the methodology, results, and uncertainties of EPA’s assessment of huma n health risks resul ting from groundwater contamination from coal-fir ed electric utilities.

Under the assumptions used in this risk assessmen t, some of the constituents that were modeled exceeded the risk criteria for lis ting as a hazardous waste (1 x 10 -5 or one in 100,000). Regarding high-end risks estimated from surface impoundment management:

• Unlined surface impoundments managing CCRs had estimated arsenic cancer risks of 2 x 10 -3 (two in one thousand), while nitrate/nitr ite was estimated to exceed the MCL by a factor of 20 and lead by a factor of 3; mo lybdenum had an estimated hazard quotient of 8, boron had an estimated hazard quotient of 7, and selenium had an estimated hazard quotient of 2.

• Unlined surface impoundments co-managing CCRs with coal refuse had estimated arsenic cancer risks of 2 x 10 -2 (two in one hundred), while lead was estimated to exceed the MCL by a factor of 9, cobalt was estim ated to have a hazard quotient of 500, cadmium an estimated hazard quotient of 9, and molybdenum an estimated hazard quotient of 3.

• Clay-lined surface impoundments managing CCRs had estimated arse nic cancer risks of 9 x 10 -4 (nine in ten thousand), an estimated nitrate/nitrite exceedance of the MCL by afactor of 10, an estimated hazard quotient fo r molybdenum of 5, and an estimated hazard quotient for boron of 4.

• Clay-lined surface impoundments co-managing CCRs with coal refuse had estimated arsenic cancer risks of 7 x 10 -3 (seven in one thousand), an estimated cobalt hazard quotient of 200, an estimated cadmium hazard quotient of 3, and an estimated molybdenum hazard quotient of 2.

• Composite-lined surface impoundments co-m anaging CCRs with coal refuse had estimated arsenic cancer risks of 4 x 10 -6 , which is less than the risk criterion.

The central tendency estimates for surface impoundments were:

• For unlined surface impoundments managing C CRs, estimated arsenic cancer risks of 1 x 10 -4 (one in ten thousand).

• For unlined surface impoundments co-managing CCRs with coal refuse, estimated arsenic cancer risks of 6 x 10 -4 (six in ten thousand), a nd an estimated cobalt hazard quotient of 20.

• For clay-lined surface impoundments managi ng CCRs, estimated arsenic cancer risks of 6 x 10 -5 (six in one hundred thousand);

• For clay-lined surface impoundments co-manag ing CCRs with coal refuse, estimated arsenic cancer risks of 2 x 10 -4 (two in ten thousand), a nd an estimated cobalt hazard quotient of 6;

• For composite-lined surface impoundments managing CCRs, or co-managing CCRs with coal refuse, estimated risks either did not exceed the risk criteria or the modeledinfiltration rate was too low for the contaminant plume to reach the nearby resident’s well during the time period of analysis (10,000 years).

One aspect of the modeling work that is important to note is the differing arrival times of various constituents, at the modeled well locations. Due to differences in behaviors when interacting in soil, some chemical constituents move more quickly than others through the subsurface environment. For unlined surface impoundments, the median number of years until peak well water concentrations would occur was estimated to be 74 years for boron and selenium, 78 years for arsenic, and 97 years for cobalt. For clay- lined surface impoundments, the median number of years was estimated to be 90 years for boron and selenium, 110 years for arsenic, and 270 years for cobalt. Of the plumes that did reach th e receptor wells from composite-lined units, 3 the median number of years was estimated to be 4,400 years for boron, 4,600 years for selenium, and 8,600 years for arsenic. The median number of years until peak well wate r concentrations for cobalt did not occur in the 10,000 year time period that was modeled.

For the high end risk estimates from landfills:

• For unlined landfills managing CCRs, arsenic was estimated to have a cancer risk of 4 x 10 -4 (four in ten thousand), while thallium was estimated to have a HQ of 3 and antimony and molybdenum both had an estimated HQ of 2.

• For unlined landfills that co-dispose CCRs with coal refuse, arsenic was estimated to have a cancer risk of 5 x 10 -4 (five in ten thousand), wh ile thallium and molybdenum were estimated to have a HQ of 2. (EPA recognizes that the industry has developed

3 In other words, based on the results from this subset of the total number of Monte Carlo realizationsguidance to improve CCR management when coal refuse is present to prevent the generation of acidic conditions. EPA solicits information on how the constituent concentrations may have changed based on current practices.)

• For unlined landfills managing FBC, arsenic wa s estimated to have a cancer risk of 3 x 10 -5 (three in one hundred thousand).

• For clay-lined landfills managing CCRs, arseni c was estimated to have a cancer risk of 2 x 10 -4 (two in ten thousand), while thallium was estimated to have a HQ of 2.

• For clay-lined landfills co-managing CCRs wi th coal refuse, arsenic was estimated to have a cancer risk the same as for clay-l ined landfills managing CCRs—that is 2 x 10 -4 (two in ten thousand).

• For clay-lined landfills managing FBC waste, arsenic was estimated to have a cancer risk of 6 x 10 -5 (six in one hundred thousand), while th allium was estimated to have a HQ of 4, and antimony was estimated to have a HQ of 3.

• For composite-lined landfills that managed CCRs or FBC waste, or that co-managed CCRs with coal refuse, the contaminant infilt ration rates were genera lly too small for the contaminant plume to reach the receptor well during the 10,000 year period of the analysis.

The central tendency estimates for landfills were:

• For unlined landfills managing CCRs, arsenic was estimated to have a cancer risk of 6 x 10 -6 (six in one million), which is less than the risk criterion.

• For unlined landfills co-managing CCRs with co al refuse, arsenic was estimated to have a cancer risk of 2 x 10 -5 (two in one hundred thousand).• For unlined landfills managing FBC waste, the modeled contaminant infiltration rates were too low to cause the arsenic contaminant plume to reach the nearby resident’s well during the time period of the analysis (10,000 years).

• For clay-lined landfills managing CCRs, arseni c was estimated to have a cancer risk of 4 x 10 -6 (four in one million), which is less than the risk criterion.

• For clay-lined landfills co-managing CCRs wi th coal refuse, arsenic was estimated to have a cancer risk of 6 x 10 -6 (six in one million), which is le ss than the risk criterion.

• For clay-lined landfills managing FBC waste, arsenic was estimated to have a cancer risk of 4 x 10 -7 (four in ten million), which is less than the risk criterion.

• For composite-lined landfills managing FBC waste, modeled infiltration rates were too low for the arsenic contaminant plume to re ach the nearby resident ’s well during the 10,000 year time period of the analysis.

As with surface impoundments, the constituents in CCRs managed in landfills did not all arrive at the drinking water well at the same time. For unlined landfills, the median number of years until peak well water concentrations were esti mated to occur was approximately 2,000 years for boron, 2,300 years for thallium, 2,800 years for arsenic, 2,600 years for selenium, and 7,800 years for cobalt. For clay-lined landfills, the median estimated time until peak well concentrations was approximately 4,000 years fo r arsenic, 5,100 years for selenium, 4,300 years for thallium, 5,600 years for boron, and 10,000 years for cobalt. Of the plumes that did reach the receptor wells from composite-lined units, the cons tituent concentrations did not yet peak in the 10,000 year time period that was modeled.As discussed in Appendix I, the Agency has evid ence that such potentially toxic constituents have leached from CCRs into groundwater fr om landfills and surface impoundments at levels exceeding the primary drinking water standards (see www.epa.gov/safewater/contaminants/index.htm l for EPA’s drinking water standards). Comparing the results of the 2009 risk assessment with the damage cases, EPA notes that the estimates for groundwater exceedances for many of the constituents in the risk assessment are the same as those found in the damage cases (arsenic, boron, cadmium, lead, molybdenum, and selenium). The differences in estimated time -to-peak-well-concentrations between unlined versus clay-lined or composite lined waste ma nagement units that are apparent for some constituents, suggest that the damage cases i nvolving contaminated drinking water may occur sooner with unlined waste management units than with clay-lined or composite-lined waste management units. This expected outcome would be consistent with the damage cases observed to date, which have been primarily found in instances where waste management units are unlined. If the groundwater modeling in the 2009 risk assessment is accurate, it may be possible to see similar damages developing from clay-lined units, in the coming decades.

Air Inhalation

Air emissions from CCR disposal sites can origin ate from waste unloading operations, spreading and compacting operations, the re-suspension of pa rticulates from vehicular traffic, and from wind erosion. Air inhalation exposures may cause adverse human health effects, either due to inhalation of small-diameter (less than 10 micr ons) “respirable” particulate matter that causes adverse effects, such as tri ggered asthma attacks or increas ed mortality (and for which theNAAQS for particulate matter has been establishe d, under the CAA), or due to the toxic effects of these respirable particles.

Potential adverse health effects from particulate matter inhalation :

To evaluate the potential exposure of residents to particulate matter that li ve near landfills that have disposed of CCRs, EPA has performed a screening-level analysis using the SCREEN3 model. This analysis, in Inhalation of Fugitive Dust: A Screen ing Assessment of the Risks Posed by Coal Combustion Waste Landfills (US EPA 2009b, copy of which is in the docket for this proposed rule), indicates that, without fugitive dus t controls, there could be exceedances of the NAAQS for fine particulate matter in the air at residences near CCR landfills. EPA requests comment and data on the screening analysis, on the results of any ambient air monitoring for particulate matter that has been conducted, wher e air monitoring stations are located near CCR landfills, along with information on any techniqu es, such as wetting, compaction, or daily cover that may be employed to reduce such exposures.

Potential adverse health effects from toxi c constituents present in particulate matter :

A description of the modeling and risks from this pathway for disposal of CCRs in landfills and surface impoundments can be found in the Draft Final Report: Non-ground Water Pathways, Human Health and Ecological Risk Analysis fo r Fossil Fuel Combustion Phase 2 (FFC2); June 5, 1998. 4 This analysis did not address the issue of enrichment of toxic constituents present in

4 www.epa.gov/epawaste/nonhaz/industrial/special/fossil/ngwrsk1.pdfthe finer, inhalable fraction of the ov erall particulate matter size distribution, 5 but used the total constituent concentrations to represent the con centrations of constituents present on the inhaled particulate matter. Based on the analysis, at la ndfills, the highest estimated risk value was an individual excess lifetime risk of 4 in one million for the farmer, due to inhalation of chromium (all chromium present in the particulate matter wa s assumed to be in the more toxic, hexavalent form). For surface impoundments, the highest risk value was 2 in one million for the farmer (again assuming all chromium present was hexa valent). The Agency requests comment on the analysis, as presented in the draft final report, as well as any data, incl uding air monitoring data that may be available regarding th e potential for residents to be exposed to toxic constituents by this exposure pathway.

Fish Consumption

Exposure for this pathway stems from human cons umption of fish that are caught in surface water bodies, such as streams or rivers, loca ted near CCR landfills or surface impoundments. There are several ways in whic h a nearby water body and, consequently, the fish in that water body, could become contaminated due to waste ma nagement activities: runoff and erosion from the landfill or surface impoundment, direct depositi on of airborne particles, the migration of contaminated groundwater from underneath the waste management unit into the nearby surface water, or even direct discharg e of surface impoundment effluent. Once the constituents are in the surface water, fish may absorb the dissolved constituents during normal respiration across the

5 See, for example, Vouk, V. and Piver, W. “Metallic Elements in Fossil Fuel Co mbustion Products: Amounts and Form of Emissions and Evaluation of Carcinogenicity and Mutagenicity.” Env Health Perspec 1983: 47(201-225).gills. In addition, contaminants that concentrat e in the sediments may be introduced into fish through the food chain. Contaminan ts can accumulate in fish from either or both of these exposure mechanisms depending on the chemical’s potential for bioconcentration and bioaccumulation.

The 2009 risk assessment addresses potential human health risks from eating fish that are contaminated due to the migration of contamin ated groundwater that migrates from underneath the landfill or surface impoundmentand affects nearby surface water bodies. Regarding highend risk estimates from surface impoundment management: 6

• Unlined surface impoundments managing CCRs had an estimated arsenic cancer risk of 8 x 10 -6 (eight in one million), which is less th an the risk criterion, and an estimated HQ for selenium of 3.

• Unlined surface impoundments co-managing CCR with coal refuse had an estimated arsenic cancer risk of 3 x 10 -5 (three in one hundred thousand).

• Clay-lined surface impoundments managing CCR ha d an estimated arsenic cancer risk of 4 x 10 -6 (four in one million), which is less than the risk criterion, and an estimated HQ for selenium of 2.

• Clay-lined surface impoundments co-managing CCR with coal refuse had an estimated arsenic cancer risk of 8 x 10 -6 (eight in one million), which is less than the risk criterion.

• For composite-lined surface impoundments managing CCR, or co-managing CCR with coal refuse, estimated risks either did not exceed the risk criteria or the modeled

6 Central tendency estimates either did no t exceed the risk criteria or the modele d infiltration rate was too low for the contaminant plume to reach the surf ace waterbody during the time period of the analysis (10,000 years)infiltration rate was too low for the contaminant plume to reach the nearby surface waterbody during the time period of analysis (10,000 years).

The central tendency estimates for landfills were:

• For unlined landfills managing CCR, the arseni c cancer risk was estimated to be 1 x 10 -6 (one in one million).

• For unlined landfills co-managing CCR with coal refuse, the arsenic cancer risk was estimated to be 2 x 10 -6 (two in one million), which is less than the risk criterion.

• Unlined landfills managing FBC waste had m odeled contaminant infiltration rates that were too low to cause the arsenic contaminant plume to reach the nearby surface waterbody during the time period of the analysis (10,000 years).

• For clay-lined and composite-lined landfills managing CCR, or co-managing CCR with coal refuse, estimated risks either did not exceed the risk criteria or the modeled infiltration rate was too low for the contaminant plume to reach the nearby surface waterbody during the time period of analysis (10,000 years).

• Central tendency estimates either did not exceed the risk criteria or the modeled infiltration rate was too low for the contam inant plume to reach the surface waterbody during the time period of the analysis (10,000 years).

Ecological Risks

For ecological non-cancer hazards that are modele d, the risk criterion is a hazard quotient that represents impacts on individual organisms, with a risk of concern being an estimated hazardquotient greater than one. In some instances, EPA also considered documented evidence of ecological harm, such as field studies published in peer-reviewed scientific literature. Such evidence is often sufficient to determine adverse eco logical effects in lieu of or in addition to modeling potential ecological risks.

Two types of exposures can occur for ecologica l receptors: exposures in which ecological receptors inhabit a waste management unit di rectly, and exposures in which CCRs or its chemical constituents migrate, or move, out of the waste management unit and contaminate nearby soil, surface water, or sediment.

For exposures in which ecological receptors directly inhabit a waste management unit, the 1998 risk assessment indicated that several chemical constituents present in CCRs managed in surface impoundments may pose adverse effects on orga nisms that inhabit those impoundments: aluminum (amphibians), arsenic (birds), bor on (amphibians), cadmium (mammals), lead (mammals), mercury (birds) and selenium (mamma ls and amphibians). Because of the large size of these waste units, many being 100’s of acres to one that is about 2600 acres, receptors can often inhabit these waste management units. Ther e are a number of recent references in the peerreviewed scientific literature specific to CCRs managed in surface impoundments that confirm the 1998 risk assessment results and provide ad ditional pertinent info rmation of potential ecological damage. Hopkins, et al. (2006) 7 observed deformities and reproductive effects in

7 Hopkins, W.A., S.E. DuRant, B.P. Staub, C.L. Rowe , and B.P. Jackson. 2006. Reproduction, embryonic development, and maternal transfer of contaminants in the amphibian Gastrophryne carolinensis. Environmental Health Perspectives . 114(5):661-666.amphibians living on or near CCR disposal sites in Georgia. Rowe, et al. (2002) 8 provided a thorough review of laboratory and field studies that relate to the impact of CCR surface impoundment management practices’ on aquatic organisms and communities. Examples of studies cited in Rowe, et al. ( 2002) that illustrates the impact of CCRs on aquatic organisms in direct contact with surface impoundment waters and/or sediments include Benson and Birge (1985), 9 Coutant, et al. (1978) 10 and Rowe, et al. (2001), 11 while examples of studies cited in Rowe, et al. 2002 that illustrates the impact of CCRs on aquatic organisms in water bodies near CCR surface impoundments include Lemly (1993) 12 and Sorensen, et al. (1982) 13 and (1988). 14 This latter category may reflect CCR impacts a ttributable to three constituent migration mechanisms: 1) NPDES-permitted discharges from impoundments; 2) overtopping of

8 Rowe, C., Hopkins, W., Congdon, G. “Ecotoxicological Implications of Aquatic Disposal of Coal Combustion Residuals in the United States: A Review.” Env Monit Assess 2002: 80(270-276).

9 Benson, W. and Birge, W. “Heavy metal tolerance and metallothionein induction in fathead minnows: results from field and laboratory investigations.” Environ Toxicol Chem 1985:4(209-217).

10 Coutant, C., Wasserman, C., Chung, M. , Rubin, D., Manning, M. “Chemistry and biological hazard of a coal-ash seepage stream.” J. Water Poll. Control Fed. 1978:50(757-743).

11 Rowe C., Hopkins, W., and Coffman, V. “Failed recruitment of southern toads ( Bufo terrestris ) in a trace-element contaminated breeding habitat: direct and indirect effects that may lead to a lo cal population sink.” Arch. Environ. Contam. Toxicol. 2001:40(399-405).

12 Lemly A., “Guidelines for evaluating selenium data from aquatic monitoring and assessment studies.” Environ. Monit. Assess. 1993:28(83-100).

13 Sorensen, E., Bauer, T., Bell, J., Harlan, C. “Selenium accumulation and cytotoxicity in teleosts following chronic, environmental exposure.” Bull. Environ. Contam. Toxicol. 1982:29(688-696).

14 Sorenson, E. “Selenium accumulati on, reproductive status, and histopathological changes in environmentally exposed redear sunfish.” Arch Toxicol 1988:61(324-329).impoundments; and 3) groundwater-t o-surface-water discharges (modeled in US EPA 2009a), as well as other, non-CCR-related, sources of pollutants.

The 2009 risk assessment addresses potential ecol ogical risks from aquatic receptors living in nearby surface waterbodies. Regarding risk estimates from surface impoundments:

• For high-end risks, unlined surface impoundment s were estimated to have HQs of 2,375 for boron, 22 for lead, 13 for arsenic V, 12 for selenium VI, 6 for cobalt, and 3 for barium.

• For high-end risks, clay-lined surface impoundments were es timated to have HQs of 854 for boron, 7 for lead, 4 for arsenic V, 4 for selenium VI, and 3 for cobalt.

• For high-end risks, composite-lined surface impoundments were estimated to have HQs of 257 for boron, 2 for lead, 5 for arsenic V, and 5 for cobalt.

• Central tendency estimates for unlined surface impoundments showed an HQ of 7 for boron.

• Central tendency estimates for clay-lined and composite-lined surface impoundments were either below the risk criteria, or the modeled infiltration rate was too low for the contaminant plume to reach the nearby su rface waterbody during the time period of the analysis (10,000 years).

Regarding risk estimates from landfills:

• For high-end risks, unlined la ndfills were estimated to have HQs of 281 for boron, 8 for lead, 2 for selenium VI, 2 for arsenic V, and 2 for barium.

• For high-end risks, clay-lined landfills were estimated to have an HQ of 78 for boron.• For high-end risks in composite- lined landfills, the estimated risks either did not exceed the risk criteria or the modeled infiltration ra te was too low for the contaminant plume to reach the nearby surface wate rbody during the time period of analysis (10,000 years).

• Central tendency estimates for landfills of all liner types were either below the risk criteria, or the modeled infiltration rate wa s too low for the contaminant plume to reach the nearby surface waterbody during the time period of the analysis (10,000 years).

The 2009 risk assessment addresses potential ecologi cal risks from sediment receptors living in nearby surface waterbodies. Regarding risk estimates from surface impoundments:

• For high-end risks, unlined surface impoundment s were estimated to have HQs of 311 for lead, 127 for arsenic III, and 30 for cadmium.

• For high-end risks, clay-lined surface impoundments were es timated to have HQs of 58 for lead, 55 for arsenic III, and 9 for cadmium.

• For high-end risks, composite-lined surface impoundments were estimated to have HQs of 4 for lead, 31 for arsenic III, and 2 for cadmium.

• Central tendency estimates for all surface impoundments were either below the risk criteria, or the modeled infiltration rate wa s too low for the contaminant plume to reach the nearby surface waterbody during the time period of the analysis (10,000 years).

Regarding risk estimates from landfills:

• For high-end risks, unlined la ndfills were estimated to have HQs of 58 for lead, 11 for arsenic III, 5 for cadmium, and 2 for antimony.

• For high-end risks, clay-lined landfills were estimated to have an HQ of 3 for arsenic III.• For high-end risks in composite- lined landfills, the estimated risks either did not exceed the risk criteria or the modeled infiltration ra te was too low for the contaminant plume to reach the nearby surface wate rbody during the time period of analysis (10,000 years).

• Central tendency estimates for landfills of all liner types were either below the risk criteria, or the modeled infiltration rate wa s too low for the contaminant plume to reach the nearby surface waterbody during the time period of the analysis (10,000 years).
While the 2009 risk assessment addresses exposure to aquatic and sediment receptors in surface waterbodies impacted by groundwater, EPA had not collected new data on impoundment water samples. Therefore, the direct exposure pa thway for ecological risk was addressed through discussion of the results of the CCW risk as sessment conducted in 1998 (U.S. EPA, 1998a,b). This assessment did consider direct exposure of ecological receptors to surface impoundment waters. The approach in the 1998 study restricted th e analysis to terrestrial receptors that obtain food and prey directly from the surface impoundme nts. The 1998 direct exposure results show:

• HQs greater than 1 for antimony, molybdenum, thallium, chromium III, zinc, beryllium, chromium VI, and arsenic III.

• HQs greater than 10 for silver, nickel, va nadium, copper, aluminum, and arsenic V.

• HQs greater than 100 for selenium IV, sele nium VI, cadmium, total selenium, barium, lead, mercury, and boron.

Seven of the proven damage cases to surface wate r identified in the damage case assessment were ecological in nature and reflect damages to fish, frogs, and other wildlife as a result of discharges from surface impoundments. The Agency notes that these disc harges are regulated by the NPDES program under the CWA and are not within the authority of RCRA. We arepresenting these cases here simply to provide information on this potential for risk to the environment.

In five cases, lakes constructed as cooling wate r sources for coal-fired power plants received discharges from the plants’ ash-settling ponds contai ning elevated levels of selenium resulting in elevated levels of selenium in fish in the lakes. The states issued fish consumption advisories and set new discharge limits for selenium. Thes e advisories have since been lifted based on results of fish tissue studies. Similarly, a fish-consumption advisory was issued by the Tennessee Wildlife Resources Agency (TWRA) in Ja nuary 2009 in response to the coal ash spill at the TVA Kingston power plant. TWRA plans to resample fish tissue on a semiannual basis and expects that the assessment of the impact of this release on wildlife resources and habitat will require repeated sampling and evaluation over th e next three to five years. In another case, coal ash was disposed of in a nearby quarry from 1967 to 1990. Concentrations of selenium, arsenic, and possibly thallium were elevated in largemouth bass from the quarry relative to bass from another nearby site, and some fish from the quarry had deformed bony structures. Higher concentrations of arsenic, selenium and lead were also found in small animals around a coal ash pond than in animals from a reference site. Finally, at another site, fly ash was sluiced (transported in water) to settling basins. A continuous flow of slui ce water exited the basins into a swamp, which discharged into a stream. Obse rvations of bull frog tadpoles inhabiting the settling basins and swamp revealed deformities and impaired swimming and predator avoidance abilities.For the risk analysis conducted for the March 1999 Report to Congress, 15 a number of publications were identified li nking adverse effects in amphibians (and other biota) with exposure to sluiced ash pumped into a series of settling basins a nd, ultimately, into a two hectare drainage swamp. This site is one of the seve n proven ecological damage case sites identified by EPA. The drainage swamp at the Savannah River Pr oject in South Carolina historically received effluent from other coal ash sett ling basins that are no longer in use (Rowe, et al., 1996). Various studies related to this site (e.g., Cherry, et al ., 1984; Guthrie and Che rry, 1979; Hopkins, et al., 1997) have demonstrated that effects ranging from mortality to sublethal effects, such as developmental anomalies, are causally linked to th e presence of elevated c oncentrations of trace elements found in coal ash residuals. In partic ular, selenium has been shown to be toxic to amphibians at relatively low levels of expos ure (e.g., Browne and Dumo nt, 1979). In addition, accumulation of selenium (a common trace meta l in CCRs) has been demonstrated in both terrestrial (e.g., Carlson and Adriano, 1993) and aquatic ecosystems (e.g., Lemly, 1985; Ohlendorf, et al., 1990; Saiki, et al., 1993). Many studies suggested that the effects were caused by the properties of combustion ash (e.g., low pH; siltation; high soluble salts concentration; pozzolanic action), as well as the trace metals in the ash.

15 Non-ground water Pathways, Human Health and Ecological Risk Analysis for Fossil Fuel Combustion Phase 2 (FFC2); Draft Final Report, June 5, 1998 available at www.epa.gov/epawaste/nonhaz/indust rial/special/fossil/ngwrsk1.pdf