Delayed once already by COVID-19 concerns, Colstrip Unit 4 will shut down for maintenance this fall, with the possibility of prolonged, and costly, outages if the work can’t be completed.
A traveling crew of roughly 500 workers is expected at the unit during a 64-day scheduled outage starting Sept. 11, this according to a July 20 NorthWestern Energy operations report. The work was supposed to take place in the spring, but was postponed because of concerns about the novel coronavirus.
NorthWestern is seeking to buy more of Unit 4 and disclosed a maintenance plan in its application to Montana regulators for preapproval of its purchase.
The rescheduled period aligns with the start of flu season, and the reopening of public schools, two events that health experts expect to exacerbate the spread of COVID-19. The work on Colstrip Unit 4 cannot be postponed again without negative results.
“While it was prudent to delay until this fall to help ensure the safety of the community, the safety of the employees at Colstrip, and the safety of contractors needed to execute the overhaul, further delay could result in a forced outage(s) that are more prolonged and more costly,” according to NorthWestern’s report.
Asked about the costs and length of future outages should the fall work be postponed, NorthWestern didn’t comment. The cost of any replacement power NorthWestern purchased on the open market during a forced outage would be split with the utility’s Montana customers. The 2019 Montana Legislature set the Montana customer share of such expenses at 90%.
If the work was completed during the scheduled 64-day fall outage, one advantage would be the low fall market energy costs. September is outside of the summer air conditioning season when the market price for energy tends to be higher.
The power plant’s coal-fired units are usually on a three-year schedule for a scheduled outage and overhaul, but it’s been four-and-a-half years since Unit 4 was last shutdown.
In 2018, Units 3 and 4 were taken offline for 77 days after failing air pollution tests
NorthWestern owns 30% of Colstrip Unit 4. It's attempting to buy another 12.5% to 25% of unit from Puget Sound Energy a Washington utility attempting to get out of the unit five years ahead of the state's ban on coal power. Puget has cited avoiding increased repair costs as one of the reasons for getting out of the unit.