Document 36VkM3KK8KJRDkr20M88G9By

USCA Case #24-1190 Docurnent #2062093 Filed: 06/27/2024 Page 21 of 92 47. In addition to depending on wholesale power prices to remain robust during the four-year period, Talen Montana's ability to recoup its investment is dependent on Colstrip's ability to operate during that timeframe. The complex power generation equipment used at Colstrip units will need to be offline for maintenance from time-to-time. Should those maintenance outages extend beyond anticipated durations, or should they occur during periods of high prices, Talen Montana could miss out on the revenues necessary to recover its investment. The relatively short recovery period of only four years exacerbates this operational risk. 48. Additionally, the cost to achieve a small incremental improvement in fPM removed is enormous. Colstrip already achieves 99.6 percent reduction of fPM with its existing wet venturi scrubbers.' The MATS Final Rule would require Since Colstrip Units 3 and 4 began commercial operations in the mid-1980s, Colstrip has continuously improved its methods for controlling air pollution. Colstrip has typically been able to remain below the current MATS limit of 0.030 lb/MMBtu of fPM. Since 2018, Colstrip has hired consultants and engineers to explore ways to further enhance the efficiencies of the venturi wet scrubbers. This work has made the venturi wet scrubber emissions more stable. Additionally, Colstrip implemented additional measures to address combustion conditions to help ensure that combustion of the coal occurs in a manner that prevents the formation of small fly ash particles that are difficult to remove in the wet venturi scrubbers. Together, these and many other comprehensive effbrts reflect upgrades available to be implemented to the Colstrip scrubber/combustion process to reduce fPM, which has enabled Colstrip since 2018 to achieve consistent compliance with the current 0.030 lb/MMBtu fPM limit with an adequate compliance margin. In 2022, based on stack tests, Colstrip's two units combined achieved approximately 0.022 lb/MMBTU fPM on an annual basis--well below EPA's limit prior to the promulgation of the MATS Final Rule. 20 Sierra Club FOIA 2025-EPA-04883 ED_018388_00000309-00021 SC_EVERSPLIT0006184