An unplanned electrical outage on Monday left Unalaskans across the island without power.
Officials are still investigating the cause of the city-wide outage that happened around 6:20 p.m., according to Public Utilities Acting Director Steve Tompkins.
"I don't have a perfectly firm answer for you on why the engine came offline," Tompkins said. "But under normal circumstances, if an engine would have come offline, then we would have been absolutely fine, because there would have been other engines that could have assumed the load. But in this case, during this time of year, we only had one engine, and it took a break."
Tompkins said during peak processing seasons, when there might be a lot of refrigeration load added to the grid, the city will typically have several engines running, so that if one fails, there's a backup engine to pick up the load.
But during the slow season, he said the city generally has just one of its four main engines up and running.
"And so there wasn't any auxiliary engine to pick up the slack. So it was a total blackout," Tompkins said.
Power was restored at different times for different parts of the island, he added.
"It was restored in most portions of the city after about 23 minutes. Once we got another engine up to speed and got it warmed up, we were able to put it online. And then we restored power first to City Hall, Public Safety, the schools and then the town."
Tompkins said power was restored to the valley around 7 p.m., after about 40 minutes.
Westward, Alyeska, and UniSea processing plants generate their own power and were not affected by the outage, he said.
The city is using a different power unit until they investigate what went wrong.