BC Hydro says erosion caused a massive hydro transmission tower to topple into the Fraser River near Surrey, B.C. Monday night, cutting power to 25,000 customers and blocking two major highways.
The fallen wires stopped traffic on the Trans-Canada Highway over the Port Mann Bridge and on the nearby Lougheed Highway, forcing morning rush hour commuters to find another way to get to work.
Hydro and emergency crews worked through the night to remove the cables and get the highways open.
Power was restored to all but a handful of customers in less than an hour. Nobody was hurt.
BC Hydro CEO Dave Cobb blamed high water levels for undercutting the 230 kilovolt tower and sending a second structure teetering so that it drooped cables across homes, roads, rail lines and through the river between Surrey and Coquitlam, east of Vancouver.
"We undertook extra monitoring and due diligence in recent days on both transmission towers," Cobb said in a statement Monday, after inspecting the site. "There was no indication that the 230 kilovolt line was at heightened risk."
BC Hydro will hire external hydrology experts and engineers to help the Crown company determine "with certainty" the cause, he said.
"We will rigorously double-check similar transmission structures that may be affected by high water levels to ensure the long-term stability of the transmission towers."
In an earlier statement, the company said it had been aware of "limited" instability in its transmission line along the river and said work was undertaken on the weekend to shore up the infrastructure.
"The affected transmission lines had been stabilized over the weekend," the company said. "Monday evening the situation deteriorated as a result of increased and unexpected erosion along the river that may have been accelerated by an unexpectedly high water flow."
Traffic was shut down for about 12 hours on Highway 1 and part of the Lougheed Highway after the collapse. CN rail service was halted by cables across the tracks and boats had to be kept away from the downed lines in the river.
RCMP Sgt. Peter Thiessen said traffic patterns returned to normal by about 3 p.m.
"All public safety issues have been addressed by the Unified Command Centre, which has now been stood down," Thiessen said in a release.
Officials estimate it will take about one month to fully complete the necessary repairs.
