Document Lgw4y5yNnLgmrXMpkZa8Np7QQ

RLR Consulting, LLC 5401 Aztec Dr Raleigh, North Carolina 27612 Phone (919) 696-7008 Fax (919) 788-0878 MEMORANDUM TO: Rae Cronmiller, NR [CA FROM: Ralph L. Roberson, P.P. lee DATE: June 16, 2023 SUBJECT: Technical Comments on EPA's Proposed Rule: Mercury and Air Toxics Standards Risks and Technology Review -- PM CEMS INTRODUCTION Recently, the Environmental Protection Agency (EPA) proposed revisions to the Agency's Mercury and Air Toxics Standards (MATS) rule.[ These revisions are the proposed response of EPA to its previously announced review of its 2020 Risks and Technology and Review (RTR).2 Among other things, EPA proposes to eliminate the quarterly stack testing option for demonstrating compliance with the filterable particulate matter (fPM) emission standard. If EPA finaIi7cs the rule as proposed, the only compliance option for will be with a PM continuous emission monitoring system (CEMS). Compliance with the proposed emission standard of 0.010 lb/10' Btu will be based on 30-day rolling averages computed from hourly PM CEMS data. The National Rural Electric Cooperative Association (NRECA) asked RLR Consulting LLC (RLR) to review EPA's proposed rule and to assist in preparing technical comments. NRFCA asked RLR to focus its effort on the EPA requirement to mandate the use of PM CEMS to demonstrate compliance with the revised fPM emission standard. REGULATORY DISCUSSION Section 112(f) of the Clean Air Act (CAA) states, among other things, "if standards promulgated pursuant to subsection (d) and applicable to a category or subcategory of sources emitting a pollutant (or pollutants) classified as a known, probable or possible human carcinogen do not reduce lifetime excess cancer risks to the individual most exposed to emissions from a source in the category or subcategory to less than one in one million, the Administrator shall promulgate standards under this subsection for such category." Then, Section 1 12(d)(6) requires EPA to "review and revise as necessary 88 Fed. Reg. 24.854 {April 24. 2023). 87 Fed. Reg. 7.624 (February 9. 2022). Sierra Club FOIA 2025-EPA-04883 ED_018388_00000327-00045 SC_EVERSPLIT0006354