Analysis - The Institute for Southern Studies

Finally, for Subtitle C, there would be federal oversight of the groundwater monitoring requirement, and therefore this RIA assumes 100% of
facilities would have contamination detected early. Looking forward, this would effectively prevent all cancers. 129 In addition, the technical
standards of the subtitle C rule would largely prevent future releases because surface impoundments would be phased-out, and because new
landfills would require composite liners. Similarly, closure requirements would largely prevent releases after closure of both types of units.
Where releases of arsenic from disposal units occur in the future, they will be detected promptly after they occur under the proposed option, as
well as under the other options where good monitoring programs are in place. In these cases, there may be response costs, but no cancer risks.
On the other hand, if facilities do not have adequate detection systems in place (and other adequate controls, e.g., liners, adequate closure, etc.),
then detection will be delayed. This RIA assumes that releases will eventually be discovered, but that detection may be on a delayed basis. To
quantify this assumed that contamination would be discovered consistently until it was all discovered. Since the rate of discovery is
unpredictable, further assumed detection would be at a constant rate, reaching 100% detection by the final year of the analysis. 130 These
discoveries were assumed not to start for six years because the first percentile of time duration until peak risks for unlined surface
impoundments occurred. Restated, this profile assumes that facilities in states that require groundwater monitoring for existing units would
generally find contamination in the future soon after it occurred, reducing response costs, and preventing cancer risks. But where monitoring
and other controls were not adequate, releases would potentially go undetected for lengthy periods, causing cancers until the contamination was
eventually detected and those residents switched to municipal or bottled drinking water. In addition, response costs would be significantly
increased. The present value of avoiding all of the risks in the baseline case is the upper-bound on benefits, and this upper bound is reduced by
detection and groundwater remediation as described in this section. The risk reduction benefit for each regulatory option is the difference
between baseline risks and remaining risks under that option. These benefits, accounting for the detection and remediation, are presented in
Exhibit 5A-10 below. Baseline expected cancer risks are accounting for detection and remediation, compared to without taking these factor
into account. Further discussion of the cancer profile can be found in Appendix K7.
This RIA projects a trend towards decreased management of CCR in surface impoundments. Facilities with surface impoundments have been
slowly moving from wet handling in impoundments to dry handling in landfills or to beneficial uses. While this trend could affect the profile
discussed above, it is unlikely to have a significant effect on risks for two reasons. First, surface impoundments, to the extent they are closed,
are typically closed with waste in place. Thus, they are likely to continue to leach beyond the 75-year period modeled in the 2009 risk
assessment; this is particularly true in situations where they are not lined (which are overwhelmingly the case) and where they are located in
states without strong regulation. In the latter case, closures are likely to be inadequate, leading to continued infiltration. Second, the releases
that occurred before the surface impoundments are closed will continue to migrate until they reach the groundwater wells or until they are
intercepted by a surface waterbody (again particularly in states without strong programs). Given the relatively very large size of the CCR
impoundments, and the presence of a hydraulic head at least before closure, these historic releases have the potential to be significant. Given
these considerations, the closure of surface impoundments in states without regulations (e.g., corrective action, groundwater monitoring, etc.)
would behave very similarly to active surface impoundments in terms of their risks to human health and the environment. For this reason, the
regulatory oversight in the options above was not modified for closed CCR disposal units.
129 Cancers from historic releases would not be affected, but the releases would be promptly identified and future exposures avoided.
130 Some releases are likely to go entirely undetected in the absence of groundwater monitoring and other controls. However, to put a reasonable limit around the analysis,
this RIA assumed 100% detection.
125