Document n9z7Dyo4kqrdgk3By78Ym8Q2a

March 28. 2025 Page 5 I. Existing PM CEMS technology is not capable of measuringf13114 emissions at the level required by the 2(124 MATS Rule. As highlighted in the forthcoming Class of '85 Letter, EPA acknowledged that PM CEMS presents technical challenges that impact the feasibility of compliance- by the 2027 deadline. Indeed, in the Rule, EPA stated that "measuring very low and non-normal high WM emissions can be challenging'' using PM CF MS." Though other continuous monitoring methods to directly measure non-mercury hazardous air pollutant metals are being developed, they are not currently available on the market.'' Because the technology necessary for compliance with this requirement is not vet available, two-year Presidential Exemptions from the use of PM (TMS at Basin Electric's affected EGUs are necessary. 2. The necessary studies, procurement, and construction of the technology necessary to comply with the new standards cannot be completed by the 2027 implementation deadline. Basin Electric is currently working with its consultants to study whether upgrades to the emission control systems currently installed at the affected EG Us are necessary to comply with the fl'M standard as well as the mercury emission standard for lignite-fired ECilIs under the 2024 MATS Rule. Consistent with the discussion of this issue in the Class of '85 Letter, continuous compliance with the 1PM standard is not possible with the emission controls currently installed at Basin Electric's EGUs. To identify necessary upgrades. Basin Electric is conducting comprehensix e emissions testing at its affected EGUs. Once the studies are complete, Basin F.lectric - s consultants will need additional time to analyze the data and identify the necessary upgrades. This process has two possible outcomes--to comply with the new tYM standard, Basin Electric will need to either completely rebuild its hydrostatic precipitators with new parts or install haghouses. limier either scenario, upgrading the emission control systems by the 2027 deadline will have direct impacts on Basin Electric's ability to reliably operate its EGUs. After identifying the upgrades, Basin Electric will have to navigate a protracted procurement process for the necessary parts and equipment. which can take up to a year. The timeline is then further complicated by the need to construct the upgrades durinit, Fkiti outages, w.hich are systematically planned by Basin Electric and approxed by electricity grids operators years in advance to prevent grid disruptions. For [eland Olds Station Unit 1 and Laramie Rix er Station Unit 1, the next available outage window for such construction will he in 2027. For Island -See EPA. Suniniary ()I Prrhhc t'ommenrs and 1?,>spon4es on Propr,yed Ride. 58 (Apr. 2(124). Ups: 7www.regulunons.gin,ds..)carnentiEPA-I IQ-OAR-20 I 8-0794-6922. 1 ' Iel {citing DemHo.ctration q'Sorbent Trapv Jhr Coniimuni ement of !vial I lal(riTA Air PolfutunH (11.4 PS) (Out 2(124). htipN:, n1s1tC. upt i coin spill esuaruh, 056617 McinonstI:ition-of'-soibunt-tiap,-fm-continnou.- measurement-of-metal-liazards-air-pollutaras-hapst. Sierra Club FOIA 2025-EPA-04883 ED_018388_00000312-00005 SC_EVERSPLIT0006290