Analysis - The Institute for Southern Studies

For the subtitle “D prime” approach, existing impoundments will not need to be lined, but can continue to operate until they close. Third-party
inspections of surface impoundments would be required under this option, but it is difficult to predict the extent to which these inspections
would actually occur and would decrease catastrophic failures. In any case, the benefits of subtitle “D prime” would be less than those of
subtitle D (version 2) and greater than the baseline in terms of costs of catastrophic failures avoided. Thus, this RIA used the midpoint as a
best-estimate of the effectiveness that these inspections would have. This results in 23% of the subtitle C (special waste) benefits being
realized in a subtitle “D prime” approach. Exhibit 5B-11 below presents the avoided cleanup cost estimates for the three regulatory options
(i.e., Subtitle C special waste, Subtitle D version 2, and Subtitle “D prime”).
Exhibit 5B-11
Future CCR Impoundment Structural Failure Cleanup Costs Avoided
($millions present value over 50-years)
Discount Rate 99 th %-ile 95 th %-ile 90 th %-ile Average
Subtitle C (special waste)
3% $16,708 $13,966 $13,043 $9,371
7% $9,423 $7,876 $7,356 $5,285
Subtitle D (version 2)
3% $7,519 $6,285 $5,869 $4,217
7% $4,240 $3,544 $3,310 $2,378
Subtitle “D Prime”
3% $3,843 $3,212 $3,000 $2,155
7% $2,167 $1,811 $1,692 $1,216
Step 5. Estimate Future Avoided Cleanup Costs for Two Alternative Impoundment Failure Scenarios (Scenario #2 & #3)
Not all of these releases are likely to pose the type of catastrophic risks that were seen at TVA’s Kingston, TN plant. Catastrophic releases are
more likely where there is a high potential for impoundment materials to disperse over large areas. This is most likely to occur at tall
impoundments. Thus, this RIA presents an alternative assumption that the Kinston-like catastrophic releases would only occur at these tall
impoundments. In addition, as age appears to be a driving factor in releases, this analysis also assumed that Kingston-like catastrophic releases
would occur at older impoundments. Particularly, 96 impoundments of the 584 covered in the 2009 EPA mail survey were at least 40 feet tall
and at least 25 years old. The analysis below assumes that 10% - 20% of these impoundments could fail within the next 20 years. This is
equivalent to the upper percentiles of failures predicted in Steps 3 and 4 above; however it moves the costs forward in time, to show the
sensitivity of the benefits with respect to time.
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