The high-running Fraser River showed its force Monday when powerful currents undercut and toppled a BC Hydro transmission tower, downing power lines and forcing the overnight shutdown of Highway 1 and the Lougheed Highway.
Now area mayors want to know whether Hydro officials should have done more to prevent the emergency and whether there are more vulnerable points in the transmission system that need to be upgraded.
“This is unfathomable,” Coquitlam Mayor Richard Stewart said. “I’m still left with lots of questions for BC Hydro as to how their line could have been undermined on the south side of the river for weeks and they had not reported it to the communities that would have been affected by this kind of calamity.”
Hydro officials said Tuesday morning they had been aware for several days that river erosion had made some towers unstable and crews worked over the weekend to stabilize them.
The situation deteriorated at 9 p.m. Monday night when one tower fell on the Surrey side, dropping its 230-kilovolt transmission cables into the Fraser, and putting a second tower at risk on the opposite bank.
Stewart said it’s lucky the two highways were reopened by 7:15 a.m. Tuesday and the region was not grappling with the gridlock that would have resulted from the shutdown of 14 lanes of traffic, including United Boulevard, which was also closed.
But he said the biggest risk was the potential for thousands of pounds of overhead cable to fall on top of motorists on the freeway
“It was de-energized but it still would have killed people,” Stewart said. “We could have had hundreds of people killed. We could have had tremendous loss of property.”
Electricity was cut off to more than 25,000 homes and businesses and caused lights to flicker or dim across a much wider area.
The power line in the river was being dragged by the current, threatening to pull down the first tower on the Coquitlam side, where the stressed metal could be heard groaning Monday night.
“It was singing loudly,” Stewart said, adding engineers were warning that if that tower went the stress on the next one would be tremendous, potentially causing a ripple effect that might have taken out more infrastructure on the north side.
At 4 a.m., he said, engineers and Hydro decided to cut the lines over Highway 1, Lougheed Highway and United Boulevard to relieve pressure. It took an hour for a bucket truck to arrive from Aldergrove and it took another two hours to cut the lines and allow traffic to flow.
Stewart called the situation “unbelievable” and said he has “lots of questions” – particularly why civic officials didn’t get earlier notification of the threat.
Surrey Mayor Dianne Watts said she also wants to ensure proper emergency protocols are followed and determine what other towers may be at risk.
“It raises some serious concerns in terms of the stability of a number of those towers on the foreshore,” she said. “Any time you have a transmission tower fall into the Fraser River there’s got to be an assessment of the other towers in close proximity.”
Watts noted the emergency also shut down the CN rail yard as well as shipping on the river.
She credited BC Hydro for working quickly to restore power and reopen highways.
BC Hydro vice-president David Lebeter is promising a full investigation and assessment of other towers along the river.
He told reporters the underwater scouring of the tower footings took engineers by surprise – they had been more concerned about a tower further upstream, not the one that actually fell.
Sagging power lines near the west end of the Port Mann Bridge and Cape Horn interchange forced the road closures and tension on lines splintered wooden power poles in some residential areas on the Surrey side of the river.
SFU geographer Jeremy Venditti said this year’s Fraser flow has been the 10th highest on record but added it’s been an extremely unusual freshet.
The river hit a high flow level of 10,000 cubic metres per second at Hope very early in the runoff season, he said, and it has kept running high for about five or six straight weeks due to the colder-than-normal spring.
“This is really the only time we’ve seen that in the last 100 years or so,” Venditti said.
He said the long period of high water completely saturated floodplain areas and weakened the soil, making the shoreline vulnerable to the formation of “scour holes” that can undercut the footings of critical infrastructure.
“It’s very hard to predict exactly when the soil is going to become unstable,” Venditti said. “Any small change in the flow patterns on the floodplain is likely to start a scour hole developing.”
BC Hydro watcher Jim Quail, who tracks the utility for the BC Public Interest Advocacy Centre, said he’s seen no sign underinvestment might be to blame for the mishap or or any indication any towers had been flagged as vulnerable to river erosion.
“I’ve never heard of this happening,” he said, suggesting it was a freak incident. “Their engineers are generally pretty conservative.”
BC Hydro has long warned it’s grappling with aging infrastructure and needs to raise rates to pay for the work, but that spending is mainly linked to dam upgrades.
Hydro is spending at least $180 million to improve the reliability of the power supply in Vancouver with its Vancouver City Centre Transmission Project, slated for completion in 2013.
A $37-million transmission upgrade is also underway in New Westminster to accommodate growing power demand.
– with files from Todd Coyne