Document Modg5NyMQdvdN6LaNXx5QD04M

USCA Case #24-1190 Docurnent #2062093 Filed: 06/27/2024 Page 11 of 123 24. NorthWestern is commencing a new rate case in July, 2024. Because of the high consequences of the MATS2 Rule, NorthWestern will be asking the MPSC for an accounting mechanism to address MATS2 Rule compliance costs. Given required statutory and administrative processes and prior experience, it is not plausible that this proceeding will be completed prior to the date by which binding commitments arc necessary to install the required controls in time to meet the 2027 or 2028 compliance deadlines. The decision points and timelines associated with fPM control contracting and installation are discussed in more detail in the declaration of Dale Lcbsack. NorthWestern and its rate paying customers therefore face financially significant uncertainty no matter how the MPSC ultimately rules. If the MPSC allows rate recovery, then the rate paying public will face substantial electric rate increases. if the MPSC does not, then North Western could be financially devastated. And North Western cannot know the answer before the investment decisions must be made. Electric grid reliability consequences of closure of Colstrip by the end 012031 or earlier 25. One option to avoid the preceding conundrum would be to simply close Colstrip by the MATS2 Rule July 2027 compliance date. But closure of Colstrip prior to the mid-2030s, and especially by mid-2027, would create other types of potentially catastrophic and irreparable risks and harms. 26. NorthWestern addressed the electrical grid reliability implications of early closure of Colstrip in its North Western MATS2 Comments, its North Western GI IG Rule Comments, and its NorthWestern Supplemental Reliability Comments. 27. In simplest form, when Colstrip is closed its generating capacity must be replaced. Capacity can be replaced in one of two principal ways: (1) new generation facilities can be built, or (2) electricity can be purchased from third-parties in the electricity market. Existing Montana 10 Sierra Club FOIA 2025-EPA-04883 ED_018388_00000310-00011 SC_EVERSPLIT0006266