The B.C. government moved Friday to reassure the public about the safety of the province’s bridges after the collapse of a span over the Skagit River on Interstate 5 in Washington state on Thursday.
Kevin Baskin, the province’s chief bridge engineer, declined to comment specifically on the Washington case while it is still under investigation. But he said the 2,700 structures in B.C.’s bridge inventory undergo a rigorous inspection process to protect the travelling public.
He said the Transportation Ministry’s experts conduct annual inspections of the bridges in addition to regular patrols by maintenance contractors. Any issues are then referred to regional bridge engineers, who assess whether more detailed study is needed.
“So it’s a three-level approach,” Baskin said. “It starts with the maintenance contractors, then the annual inspections and then anything that needs to be addressed in more detail gets elevated from there.”
Early reports indicate that an outsized truck hit the Washington state bridge, causing part of the 58-year-old span to collapse and sending a car, truck and a travel trailer into the Skagit River north of Mount Vernon. Three people were pulled from the water with minor injuries.
Baskin said B.C. has a number of through-truss bridges of the kind that collapsed in Washington. The bridges, popular in the 1950s and ’60s, were built with less vertical clearance than is required today.
B.C. addressed that problem a number of years ago by raising the vertical clearance on those types of bridges, Baskin said.
“The steel through-trusses that we have on our main highway system all meet the current vertical clearance requirements for new bridges,” he said.
Baskin said there are still other types of bridges in B.C. with clearance issues. “We do have a database of that sort of information, so if there are vehicles that are overheight or overwidth, they need a permit,” he said. “We know what the clearances are so we can direct them to where they need to go to travel safely.”
Baskin said there is a vast range in the age and size of bridges across B.C., from the large spans on the Lower Mainland to smaller ones in remote areas. The average age is 32 years.
“We do have an aging inventory, just like the rest of North America. So that is a challenge for us, the same as it is for all other jurisdictions.”
But David Harvey, a bridge specialist with Associated Engineering in Burnaby, said it appears the age of the Washington bridge was less of a factor in its collapse than the blow it sustained from the overheight truck.
“It doesn’t have anything to do with the aging aspect in this particular case because, when it collapsed, the load on the span was extremely light,” he said. “It looks very strongly as if it were damage by the overheight vehicle which caused it, which is only to do with age in the sense that clearance standards have increased since 1955.”
He said older bridges have remained safe for years with the aid of regular inspections.
