Document XR2E48V8poY81yGm86m8mBR9g

this low. In addition, operational limitations could hinder the units' ability to continuously comply with the fPM standard. Although some units may be able to achieve a rate of 0.010 lb/MMBtu under certain conditions, the Rule requires continuous compliance. Even units that can achieve the limit in ideal conditions may not be able to continuously meet that limit during peak load conditions when they cannot do maintenance and cleaning of PM controls. During peak conditions, most units operate at base load and run at high-capacity factors. It may be difficult to maintain optimal operation of control technologies during peak conditions unless there arc additional outages scheduled for such maintenance, which may not always be feasible. Other operational factors such as filter change-out frequency of haghouscs impact the performance of controls and, thus, the facility's ability to comply with the proposed limit. These issues make continuous compliance with the fPM standard difficult to ensure. b. CENTS Technology is Not Available The MATS RTR requires coal-fired units to implement the revised FPM standard using CEMS. As explained above. this requirement is an integral part of the numeric limit itself. Oak Grove does have PM CFMS; however, these CFMS have not been calibrated and certified to reflect the revised, lower standard. There are technological limitations, as well as costs and market limits, that make using the existing CEMS to demonstrate compliance with a significantly lower 1PM standard by July 2027 unavailable. PM CEMS does not provide direct measurements; it uses correlation curves to calculate emissions levels. However, the low fPM standard in the Rule makes developing this correlation curve - virtually impossible." PGEN Comments at 22 (citing PM CEMS Technical Memo at 3). Similarly, the QA/QC criterion for CEMS are extremely difficult to meet at such low levels. See ("ommems. of the C'las's of '85 Regulauy R C.SpO/7.5 e Gran!) on the I'ropovul HcilardOPS Ail' Coal- and Oil-Tired Alectric I "Wily ,S'teatn Generating Units Review of. the Residual Risk and Technolo*, Review, Docket No. EPA-HQ-OAR-2018- 0794-5989, at 16 (June 28, 2024) [hereinafter "Class of '85 Comments"]. In fact, at the time of the proposed MATS RTR, no commercially available PM CFMS would have been able to meet the tight confidence and tolerance intervals associated with the low proposed fPM standard. PGEN Comments at 23 (citing PM CEMS Technical Memo at 5). EPA was, thus, forced to address these issues in the final MA TS R FR by loosening the QA criterion and correlation procedures. Sc.q.' 89 Fed. Reg. at 38,528-29. I Iowever, it has not yet been shown that these changes are enough to address the fundamental issue that PM CFMS have difficulty reliably measuring such low fPM levels due to the error rates of the instrument. See PUEN Comments at 23 (finding insurmountable the "uncertainties inherent in the measurement device" and the - problems associated with relative size of the uncertainty to the limited data range of fPM concentrations and the confidence levels and tolerances- ); see also Class of '85 Comments at 18. And, in reality, units would need to target emissions below 0.010 lb/MMbtu in order to ensure. compliance. See Pet'rs' Brief at 72. Therefore, the CEMS technology to demonstrate compliance with the revised f-PM standard is unavailable. III. It is in the Interest of National Security to Issue an Exemption for the Rule The requested exemptions from the Rule's lignite mercury standard. revised fPM standard. and CEMS requirement arc in the national security interests of the United States. the Rule 4 Sierra Club FOIA 2025-EPA-04883 ED_018388_00000159-00004 SC_EVERSPLIT0005928