Document dn7EjXnpdvrwmQxoyM3OzJw15

Plwe 3 of .3 1. Evaluating Optimization of Existing ESPs, 2. ESP Upgrades and Retrofit Strategies, 3. Alternative PM Control Technologies 4. Control Technology Engineering Cost Estimates, and 5. Control Technology Evaluation Trials. Based on this review, Ameren believes at a minimum that a retrofit of Labadie Units 3 and 4 ESPs will be required, and Sioux Energy Center will require significant ESP maintenance to meet the new MATs f-PM limit. The Labadie Unit 3 and 4 ESP retrofits will include replacing "A" and "3" ESPs with a new "D" ESP. The required time to complete engineering, procurement, construction, outage tie-ins, and performance testing will extend beyond the July 8', 2027, compliance date. Even with the most optimistic timeline, Amercn is uncertain if retrofits can be completed with an additional one-year extension allowed by CAA Section 1 12(i)(3)(b). Given recent supply chain disruptions and the long lead procurement times for critical energy infrastructure equipment, delays in the schedule are likely to occur. Due to the uncertainty, Ameren is requesting the two-year Presidential Exemption. Amercn Missouri has several customers that are critical to the National Security interests of United States. Ameren electric generators provide energy into both Missouri and Illinois markets where several military facilities and critical national defense suppliers are located including Scott Air Base, US Geospatial Institute, Boeing, US Steel, Cerro Copper, and others. Grid reliability is necessary for the uninterrupted operations of these entities which arc paramount to national security considerations. Ensuring that these entities can focus on serving the National Security interests of this nation and not have to deal with electric grid reliability meets the national security requirement of the Presidential Exemption allowance. Ameren Missouri believes that ample justification has been provided to support a decision to grant a two-year Presidential Exemption in accordance with the Clean Air Act for Labadie and Sioux Energy Center. Please contact either Nicholas Bound (618-771-7042) or Michael Hutcheson (314-554-2089) at your convenience if you have any questions regarding this request. Sincerely, Craig J. Gicsmann, P.E.. P.M.P. Sierra Club FOIA 2025-EPA-04883 ED_018388_00000111-00003 SC_EVERSPLIT0005800