Final Revised Supplemental Finding and Results of the Residual Risk and Technology Review
On May 22, 2020, EPA published in the Federal Register a reconsideration of the appropriate and necessary finding for the Mercury and Air Toxics Standards, correcting flaws in the 2016 supplemental cost finding while ensuring that power plants will emit no more mercury to the air than before. After primarily considering compliance costs relative to the HAP benefits of MATS, EPA is concluding that it is not "appropriate and necessary" to regulate electric utility steam generating units under section 112 of the Clean Air Act (CAA).
EPA is also taking final action on the residual risk and technology review (RTR) that is required by CAA section 112. The results from the RTR show that emissions of HAP have been reduced such that residual risk is at acceptable levels, that there are no developments in HAP emissions controls to achieve further cost-effective reductions beyond the current standards, and, therefore, no changes to the MATS rule are warranted.