Ice jam knocks Aishihik hydro plant offline

An ice blockage knocked the Aishihik hydroelectric plant offline Jan. 17, causing brief power outages throughout the territory.

An ice blockage knocked the Aishihik hydroelectric plant offline Jan. 17, causing brief power outages throughout the territory.

Yukon Energy spokesperson Janet Patterson told the News the ice “starved the hydrogenerators of water,” resulting in the plant’s shutdown.

The power went off just after 7:35 a.m. that day, causing outages in Dawson City, Carcross, Tagish, Marsh Lake, Teslin and subdivisions south of Whitehorse.

Yukon Energy and ATCO crews restored power about 40 minutes later.

When the News spoke with Patterson the afternoon after the outage, the Aishihik plant was still offline.

Crews sent an underwater camera last night to have a better look at the ice blockage.

“There is six to eight inches of what appears to be slushy ice … covering the whole trash-rack,” Patterson said late last night via email.

“Divers will be coming in on the late flight tonight and we will dispatch a crew along with the City of Whitehorse steam truck out to Aishihik tomorrow morning.”

She said she hopes to have the ice removed by end of day today or tomorrow.

The Aishihik plant, 140 kilometres north of Whitehorse, is a hydro plant built 120 metres below ground. The water drops 174 metres before reaching the plant’s turbines.

The ice jam blocked the aboveground water intake tunnel.

Backup LNG and diesel generators have been providing electricity to the grid. Operations at the Mayo and Whitehorse dams continued without interruption.

The Aishihik plant can generate up to 37 megawatts of electricity. In comparison, the Whitehorse dam generates up to 40 megawatts during its peak production period in the summer.

Right before it went offline, the Aishihik plant was generating about 30 megawatts for the grid, Patterson said.

“This is an example of why we need backup power,” Patterson said. “Even though we don’t like to use LNG or diesel, it gets people’s power back on.”

At press time, about 30 per cent of the grid’s electrical output was coming from diesel and LNG, according to the Yukon Energy website. That figure typically averages between zero and eight per cent of total generation.

Contact Pierre Chauvin at pierre.chauvin@yukon-news.com

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