Washington state's transportation department has known since the 1970s that the Interstate 5 bridge that recently collapsed after being clipped by a truck hauling an oversize load had been struck repeatedly before by similar big rigs.

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Washington state’s transportation department has known since the 1970s that the Interstate 5 bridge that recently collapsed after being clipped by a truck hauling an oversize load had been struck repeatedly before by similar big rigs.

Just last fall, a tall vehicle crossing the Skagit River bridge hit the overhead structure, ripping a 3-inch gash in the steel and deforming three components.

Even knowing that history, state officials didn’t take precautions as they often do to prevent truckers from hitting overhead structures, raising questions about whether the state could have done more to prevent the collapse from happening.

The Associated Press found that the DOT regularly puts detailed warnings on its trucking permits when routes are projected to encounter potentially problematic areas of low clearance. But the Skagit bridge – along the crucial I-5 corridor between Seattle and Vancouver, British Columbia – was never added to that group.

Federal transportation investigators believe an oversize load struck the bridge last month, causing a portion of it to collapse into the river and taking two vehicles with it. Nobody was seriously injured, but the failure has continued to disrupt transportation and renewed attention on the condition of the nation’s infrastructure.

DOT spokesman Travis Phelps said the agency puts out the caution notifications on some areas that have had clearance problems in the past – but that not every clearance height is noted. The state didn’t consider the Skagit bridge to be particularly problematic.

“We don’t put every bridge that’s been struck onto a permit,” he said.

In the DOT permit to allow the oversized load across the bridge, the state determined that the route was OK for a load that stood 15 feet 9 inches tall, even though the outer edges of the bridge had a clearance of less than 15 feet.

DOT did add a qualification that the agency does not guarantee the height clearances, and Phelps said it is the company’s responsibility to ensure that the load safely passes across. The state also provides separate information to companies about bridge heights.

The permit, however, was much different than another approval given just two days earlier to the same company. In that request, Mullen Trucking sought to bring a large boiler along Interstate 90, with a maximum height of just 14 feet.

At 10 points on the route path, the DOT issued a “CAUTION” notice, detailing the height of the overhead clearance and asking the driver to take a different route if the load was within two inches of that level. None of those overhead heights were a problem on that specific permit because they were at least seven inches higher than the load.

The problems over the Skagit first started appearing in handwritten inspection notes in 1979, when an inspector noted what he deemed “minor dings” in various components, according to records reviewed by AP.

A 1985 inspection specifically described “high load dings” on the first overhanging portions of the bridge that vehicles would encounter as they drive southbound – apparently the same parts that were compromised in last month’s collapse. Similar notes appear in other inspections as well.

Last October, a DOT bridge maintenance specialist notified another official about the large gash in the northbound portion of the bridge and the other damage that appeared to accompany it. Images show the effects of the impact on the steel, with one portion peeling back like a torn piece of paper and left pointing down the roadway. A patch of gray paint is completely gone, exposing some older green paint and the brown metal underneath.

DOT officials decided the damage wasn’t severe enough to warrant an emergency, but the department worked to mend the metal and conduct a special inspection of the span.

Washington Sen. Michael Baumgartner, R-Spokane, said DOT should take a stronger oversight role in oversized vehicle permitting to make sure such hits don’t keep happening. He’d like to see the department prohibit vehicles from traveling in areas where their loads might strike overhead portions, and said officials could automatically offer alternative routes to those drivers.

Baumgartner said it was a huge risk to rely solely on the driver to safely navigate the route, especially when it may mean that the driver has to be in a specific lane.

“That’s just an unacceptable risk to take,” Baumgartner said.

The Skagit bridge is deemed “fracture critical” because it can collapse if a single, vital component of the span is compromised. A preliminary report from the National Transportation Safety Board determined that it failed last month because the impact of the oversized load on the overhead portions of the bridge caused significant damage to those critical elements.

The driver told investigators that he felt “crowded” by another vehicle that was passing him as they arrived at the bridge, so he moved his vehicle to the right.

Crews opened a temporary replacement for the bridge this week, allowing motorists to cross at a slower speed. The state hopes to have a permanent replacement built in the coming months – although much of it will remain in its current size and style.

DOT is not allowing oversize loads to travel the temporary Skagit bridge. Phelps said it’s not clear if drivers will get a caution statement for the span when the permanent replacement reopens. “We’re going to wait and see what the investigation of the NTSB uncovers,” Phelps said.

AP Writer Mike Baker can be reached on Facebook: http://on.fb.me/HiPpEV