Document ekN8voYp8NG87wOZJY6nXBXp

USCA Case #24-1190 Document #2062093 Filed: 06/27/2024 Page 26 of 123 closures of multiple plants in neighboring states. I also do not believe that transmission would be available even if we located a source from which `ye could purchase capacity (especially with the closure of Colstrip), which Michael Cashcll addresses in his Declaration. 64. As undesirable as it would be for NorthWestern to have to purchase capacity on the market as an alternative to Colstrip, the scenario in which we are not able to obtain needed capacity (and/or arc not able to obtain transmission for such capacity) is much worse. Under this scenario, the possibility of rolling blackouts during periods of extreme weather becomes more likely. The rolling blackouts in California during the summer of 2020 and the multi-day blackout in much of Texas during February, 2021 show that utility systems in the United States can experience significant and damaging capacity shortfalls. During the cold snaps in the winters of 2022-23 and 2023-24, the Montana electrical grid was stressed to the maximum. A significant transmission or supply generation resource failure would have likely led to being unable to serve customers. 65. Equally importantly to the raw amount of electricity available, Colstrip plays a critical voltage-maintenance function. Closure would therefore require major investments in voltage maintenance, independently of the concerns about market electricity availability and transmission capacity. These concerns are discussed in more detail at page 59 of the 2023 IRP. 66. If NorthWestern is not allowed to obtain the capacity it needs, customers and communities could also suffer from blackouts. Blackouts cause serious property damage, business disruption, and even death. It is estimated that approximately 250 people died in Texas as a direct consequence of the 2021 power disruptions. This was when temperatures were in the teens. This past January our Montana service territory experienced temperatures as low as -45F in our towns. Rural areas likely experienced even colder temperatures. 25 Sierra Club FOIA 2025-EPA-04883 ED_018388_00000310-00026 SC_EVERSPLIT0006281