Document 37QbDmaq177J143O76vdrGpQJ

P;iuc 2 01- .3 reliability of the St. Louis, Missouri electric grid and increasing energy costs for our customers. Granting a two-year compliance exemption will enable Amcren to further evaluate compliance options and limit reliability and consumer pricing impacts, in furtherance of the national security interests announced by the Trump Administration. Achieving compliance with the new MATS requirements by 2027 includes several challenges related to the availability of technology, including: (1) the ability to meet the quality assurance requirements for PM CEMS required by the rule to measure fPM emissions within the criteria required by the Final Rule; (2) the ability to design, to acquire, to install and to commission cost effective control technologies capable of achieving the new MATS fl'M emissions standard; and (3) the ability to do all of this consistent with grid reliability concerns resulting from unit shutdowns necessitated by control installation, which will reduce available generating capacity. During the public commenting process, commenters highlighted significant concerns with the impact of reducing the PM limit on meeting the required Performance Specification 11(PS-11) in Appendix B of 40 CFR Part 60 and Procedure 2 in Appendix B of 40 CFR Part 60 quality assurance testing and correlation requirements at individual units, which is necessary to meet the rules' fundamental requirement to collect, record and submit to EPA continuous quality assured PM CEMS data for each affected unit. Under the MATS rule, every hour that a PM CEMS is unable to provide quality assured data is a violation of the rule. Because the new MATS limits for fPM also reduce the allowable range of acceptable test results necessary for satisfying the criteria for PM quality assurance performance testing defined in PS-1 l, affected units will be out of compliance every time they arc unable to meet the new more restrictive certification requirements. Given the challenges to quality assure PM CEMS, achieving continuous compliance with the MAT's rule monitoring requirements is infeasible without the requested compliance exemption. Ameren has been working with EPRI to develop other continuous monitoring methods to measure non-mercury ha7ardous air pollutant metals directly, such as non-mercury sorbent trap technology, but the technology is still in the process of being developed. In the absence of available technologies to reliably monitor f-PM on a continuous basis, EPA should grant Ameren a two-year compliance exemption to allow development and demonstration of the necessary technology. Ameren also raised concerns about the cost and technical assumptions associated with achieving the new f-PM limit. To comply with the original MATS limits, Ameren installed new state-of-the-art Electrostatic Precipitators (FSPs) on two units in 2014 and 2015. The cost of these retrofits was considerably higher than EPA's cost assumptions used to justify the MATs rule. In addition to the higher costs, the OEM guaranteed emission rate for the new ESPs was higher than the new emissions rate required in the MATs rule. Based on currently available information, Amercn believes it will be difficult to receive a vendor guarantee that can consistently and reliably achieve the new MATS rule requirements. Furthermore, receiving a vendor guarantee that a control device can achieve an emission rate at the emission limit does not guarantee compliance and does not provide compliance margin to allow for operational flexibility. Ameren has been performing a due diligence review to address these issues and to determine an appropriate cost-effective compliance strategy to meet the reduced fPM limit. Those evaluations include, but are not limited to, the following: Sierra Club FOIA 2025-EPA-04883 ED_018388_00000111-00002 SC_EVERSPLIT0005799