A Case Study of Risk-Based Closure for CCR Management Areas at a Coal Fired Power Plant: A guide for potential future changes to corrective action und

Prior to the 2015 CCR Rule, Barr Engineering assisted a confidential utility client with a risk-based closure of several portions of their facility. While risk-based closure of former CCR units does not meet the requirements of the current rule, the EPA has signaled that there may be relief coming to the power industry including several important reforms that industry has requested. One of these reforms is to allow for corrective action requirements under 40 CFR Part 257.95 through 257.98 to include risk based evaluation using generic or site-specific risk based thresholds regardless of whether concentrations are above background concentrations. In other words, the groundwater protection standards would be based on evidence of Appendix IV parameters at concentrations that would adversely affect receptors. This is opposed to the current situation in which concentrations above background trigger corrective action regardless of whether a receptor is present or whether the likely concentrations would negatively affect the receptor. At the site, the primary receptor is a major river. Detailed groundwater monitoring, sample analysis and modeling were utilized to assess current concentrations of CCR constituents reaching the river. Some of the CCR management areas were planned to be removed and some were left in place in accordance with the pre-CCR Legacy rule requirements. The result of the detailed evaluation and modeling predictions indicated that concentrations would not adversely affect the ecological receptors in the river. Post-remediation groundwater monitoring supported the modeling results. Independent third party experts and a state agency provided oversight of the methods and concurrence that no additional remedial actions were warranted or necessary. This example provides insight into how a risk evaluation process can be applied to demonstrate environmental protection while avoiding costly and unnecessary corrective action.