Custom-built cable sweeper ditched on Port Mann Bridge

After falling 'ice bombs' first terrorized motorists driving across the Port Mann Bridge in Dec. 2012, the B.C. government promised a custom-made system to control ice and snow buildup on the span but instead installed a low tech solution.

"A custom-designed cable sweeper has been developed that will be fitted around the bridge cables and used to remove snow and ice before it can accumulate," said a Ministry of Transportation news release dated Jan. 21, 2013.

At the time, the sweepers were apparently already being fabricated but in Dec. 2013, it was less sophisticated snow collars that debuted on the bridge's 288 cables.  

"As we were developing and working through logistics of how the sweepers would work, we actually came up with the collar system idea," said Norm Parkes, executive director of highway operations. 

"It appeared to be a much simpler approach — simple in its application, easy to deploy and effective, so we moved away from the sweepers and toward this collar chain system." 

The cost of the cable collars was paid for by the builder of the bridge, according to Parkes, who said he doesn't know if the collars were cheaper than the sweepers. 

Cable sweeper 

The custom snow sweepers were two feet long and consisted of a set of wheels, scrapers and brushes that would be raised and lowered along the cables during wintry conditions to remove ice and snow buildup.

They were to be installed starting in Jan. 2013 on 152 of the 288 bridge cables that cross the roadway of the bridge.  

Then-transportation minister Mary Polak said the sweepers would be positioned at the bottom of the cables and be manually winched up to the top and dropped back down to clear snow when required.  

"One of the things with the sweepers that we needed to think about was the cables that pulled them up and down and how those cables would act in a snowstorm," said Parkes.

"That's something that made us think more to the gravity dropped collars."  

Cable collars 

Cable collars are rings that weigh approximately 10 kilograms. 

Each one is released manually from the top of the tower and clears snow as it travels down the cable. 

"There's absolutely no disruption to traffic," said Parkes. 

Other solutions 

The problem of falling snow and ice plagues many cable-stayed bridges in snowy climates around the world. 

In most cases they simply shut the bridge, according to Parkes. 

"I believe in New York, they just have guys go out with baseball bats and hit the cables to start them shaking." 

Ice bombs continue to fall 

As of Dec. 12, ICBC reported approximately 50 claims for vehicle damage due to snow and ice falling from the Port Mann Bridge and another 95 incidents on the Alex Fraser Bridge. 

"Maybe we wouldn't be facing these problems if they had done what they said they were going to do," said NDP transportation critic Claire Trevena in response to the government's switch from sweepers to collars on the Port Mann Bridge. 

"Why the government made this choice we don't know. Nor do we know whether the sweepers are a more expensive approach ..."

"But you get promised one thing and you get no explanation why you're not having it, you get a bit suspicious." 

"Our engineers and our snow and ice experts tried to find the best solution we could," responded Parkes. 

"This collar system was the way to go."