The Whitehorse Fishway allows returning Chinook salmon to bypass the Whitehorse Rapids Power Dam the during their annual spawning run on the Yukon River.Mike Thomas/The Globe and Mail
Hydro generation at the Whitehorse Rapids Dam was shut down by ice for three days, costing Yukon Energy almost $200,000 to power diesel generators that replaced the lost power.
Yukon Energy spokeswoman Janet Patterson said Tuesday that the frazzle ice, that has the consistency of a slushy, moved to the dam and when it made contact with underwater debris grates protecting the intake pipes it froze solid.
The power was shut down Saturday evening and wasn't fully restored until Monday.
Ms. Patterson said while problems with frazzle ice occur occasionally at the dam, nobody can remember an incident this serious, when the entire hydro capacity was lost.
When the power went down, diesel generators at the dam and in Dawson City and Faro were brought online to replace the loss of all four hydro units, including a 20-megawatt turbine, the largest unit in the Yukon.
The Aishihik and Mayo hydro plants were also brought up to near capacity to help compensate for the loss, she said.
Ms. Patterson said Yukon Energy is estimating it burned 159,000 litres of diesel fuel as result of the icing, at a total cost of $197,000.
"So we contacted divers from Vancouver because there is no company here that does this type of work and we flew them in Sunday," she said.
"They spent yesterday working … with a steam wand, putting steam to the ice and melting it."
The divers installed underwater cameras so that the work could be monitored for both operational and safety reasons, she explained.
She said only one diver at a time goes in, and stays in for an hour so as not to get too cold, but the work is being watched from the surface at all times.
Ms. Patterson said this is the type of emergency situation that clearly demonstrates the need for some type of immediate backup generation, whether it's powered by diesel fuel or natural gas.
"If you think about it, we lost our whole hydro generation in Whitehorse, and nobody lost power," she said.
Environment Canada meteorologist Doug Lundquist said the average daily temperature for Whitehorse has been two degrees above normal over the past 30 days.