Analysis - The Institute for Southern Studies

programs. Groundwater remediation costs and cancer costs under the baseline and each regulatory option are then estimated. Finally, the
aggregate benefits from each regulatory option (incremental to the baseline) are estimated.
Step 1. Categorize CCR Disposal Units by Type
This step begins with the baseline data on CCR disposal (i.e., disposal unit liner types, annual CCR disposal tonnages) contained in Appendix
F of this RIA for the 495 coal-fired electric utility plants. A subtotal 84 of the 495 plants dispose CCR offsite only, and thus, no liner type is
assigned to these facilities in this benefits analysis. 106 Some of the plants have multiple data entries because they were known to have multiple
CCR disposal units on-site. This estimation step assigned only the riskiest disposal unit type and liner type combinations of those listed for
each such plant, which resulted in the six combinations displayed below in Exhibit 5A-1. 107 This hierarchy was based on the 90 th percentile,
trivalent arsenic cancer risks in the EPA-ORCR 2009 CCR risk report as follows, with those units posing the greatest risk appearing first.
Appendix K1 presents further information on CCR disposal unit liner types and associated data.
These plants were then further divided by the type of waste disposed in the units; CCR only or co-managed wastes. The ratio of facilities that
only dispose CCR compared to facilities that co-manage CCR with coal refuse is displayed below in Exhibit 5A-1. These ratios allowed EPA
to model a single number of potential cancer cases as a best estimate. The data used in the 2009 risk assessment 108 were from a 1995 EPRI
survey. Thus, there is some uncertainty regarding the current accuracy of these ratios. To account for this uncertainty, EPA also calculated a
bounding range of cancers based on the assumption that all facilities would dispose of CCR only, and that all facilities would co-manage CCR
with coal refuse only.
Exhibit 5A-1
Categorization of CCR Disposal Unit Types
CCR Disposal Unit Type CCR Only Co-managed
1. Unlined Landfill 66% 34%
2. Clay-Lined Landfill 74% 26%
3. Composite-Lined Landfill 53% 47%
4. Unlined Surface Impoundment 32% 68%
5. Clay-Lined Surface Impoundment 48% 52%
6. Composite-Lined Surface Impoundment 71% 29%
106 Note: 83 facilities in Exhibits E2 and E4 of the 2009 risk assessment are not assigned WMUs or liner types, 5 fewer than indicated in this RIA.
107 Multiple CCR disposal units at a single industrial facility will all affect the same surrounding population. To avoid duplication of population risks, the analysis used the
simplifying assumption that the human health risks will be driven by the riskiest single WMU, when multiple waste management units are present, but populations around
all WMUs are accounted for in Appendix K2 of this RIA.
108 Source: EPA “Human and Ecological Risk Assessment of Coal Combustion Wastes,” Office of Resource Conservation and Recovery, December 7, 2009.
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