As icy missiles rained from the Port Mann Bridge, the Crown Corporation tasked with managing the bridge scrambled to find some way of stopping this from happening again.
And according to documents obtained by Global News under the Freedom of Information Act, B.C.’s Transportation Investment Corporation came up with some pretty diverse solutions.
“Everyone is in crisis mode and stress levels are high,” the corporation’s vice-president of technical services said in an email Dec. 20, a day after the ice bombs. “But we need to control this as there are no simple, fast, easy answers for the issue at hand.”
And as they cast around for solutions, they tried to ascertain why the problem wasn’t prevented in the first place.
The bridge was designed bearing in mind weather events that come around once every 20 years; but this was not one of those events, according to notes from a Dec. 20 meeting.
The Port Mann’s designer called the ice bomb event “a ‘Perfect Storm’ with respect to precipitation, dew point and relative humidity” leading to a quick buildup of “heavy sticky wet snow.
“More information is needed to understand the cause,” the notes say.
In a series of emails sent back and forth between TI Corp, contractors Kiewit and Flatiron and designers TY Lin, engineers brainstormed a variety of technologies to help with the issue. “Right now we are focused on quick fix and interim solutions,” wrote Stephen Docherty of TI Corp.
Ideas discussed in emails and at meetings included vibrating or hitting cables to shake off snow or ice, as well as finding coatings to prevent ice buildup. Ski wax and Teflon were both floated as options; one email suggested a coating called “NeverWet.”
TI Corp and Kiewit/Flatiron staff contacted helicopter companies, the US Army Corps of Engineers, bridge designers in northern Europe, engineering professors, and others for input on ways to solve the ice problem.
In the end, it seems they settled on two possible solutions. The first is cable sweepers – a series of brushes and scrapers that travel up and down the cables, sweeping snow away. According to a TI Corp media release from Jan. 21, the plan is to install them on the 152 cables that cross the roadway. Some interim installation has already been completed.
Four types of hydrophobic coatings are also being tested, says TI Corp. spokesperson Max Logan. According to the media release the corporation has chosen a de-icing spray similar to those used on aircraft, that would create a barrier between the cable surface and snow in bad weather.
According to Logan, Kiewit/Flatiron paid for the design and preliminary installation of the cable scrapers. As testing is still ongoing, he said that it is premature to estimate the costs associated with all of the longer-term solutions. But he expects the contractor to cover those costs.
“Once the longer-term solutions have been confirmed, we expect the arrangement will be the same.”
Comments