The EPA published a proposed rule to modify the final Coal Combustion Residuals (CCR) Disposal Rule, published April 17, 2015. Issues covered by the proposal included the height limitation of the vegetative slopes of dikes; the type and magnitude of non-groundwater releases that would require a facility to comply with some or all of the corrective action procedures set forth in the final CCR rule; and adding boron to the list of contaminants in appendix IV of the final CCR rule that trigger's the corrective action requirements under the final rule. Further, the Agency proposed alternative performance standards for owners and operators of CCR units located in States that have approved CCR permit programs, as well as other potential revisions based on comments received since the date of the final CCR rule and petitions for rulemaking that were granted on September 13, 2017. The Agency is addressing these issues in two final rules; this action is the first of the final rules.