Putting it on ice

If there is an apodictic truth about humans, it is that we are only human. We have made mistakes, and we continue to make mistakes. Sometimes, we even repeat mistakes that we, or other humans, have made previously.

Arguably, this was the case a few weeks ago in Metro Vancouver, when chunks of ice plunged down upon unsuspecting motorists on the newly opened Port Mann Bridge. On December 19, it was actually cold enough to facilitate some sort of precipitation other than rain. We experienced snow in Vancouver, and the end of the world hadn’t even arrived!

Accumulated snow and ice on the cables of the bridge fell to the bridge deck, some of them smashing into vehicles. ICBC fielded 60 claims related to accidents on the bridge, many resulting from falling ice and snow. One driver was hospitalized.

This was unexpected in winter conditions, even those as comparably mild as Vancouver’s. Except, this type of incident has occurred before. On the same type of bridge.

As the NDP’s transportation critic Harry Bains rightly points out, we should question whether the engineers examined this type of risk on other similar bridges in other regions “like Sweden, Britain, and Boston. Perhaps, also in Seattle.”

Boston.

As part of a multi-billion dollar highway upgrade called the Big Dig, a ten lane cable-stayed bridge was built in Boston, called the Leonard P. Zakim Bunker Hill Bridge. It is the same number of lanes and basic design as the new Port Mann Bridge.

Since opening in 2003, there have been three incidents of ice falling from the bridge cables on the Zakim Bridge: in 2005, and twice in 2011.

While Boston has a harsher winter climate than Vancouver, we might rightly have asked if such incidents are possible here. After all, it snows in Metro Vancouver, and ice is not uncommon. Despite this, the new Port Mann bridge does not have heated cables to melt accumulating ice, and the engineering firm responsible, TI Corp, has admitted that the coating on the cables did not abate ice buildup. In addition, the cables cross over the bridge deck, which means falling ice and snow is likely to strike the bridge deck, unlike other bridges where the cables connect near the outside edge of the towers and do not cross over the roadway (for instance, the Alex Fraser bridge, also in Metro Vancouver).

So whether the design of the new Port Mann bridge is simply inappropriate for winter climates which include snow and ice (including Vancouver), or whether heated bridge cables would have been an expensive, but practical solution to preventing falling ice, someone made a mistake. And given that it has happened elsewhere (Boston), we should learn from that experience. What is less important than who is at fault, is what we should do to fix the bridge to avoid another ice incident the next time it gets cold in Vancouver.

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