The collapse of the Interstate 5 Skagit River Bridge has caused an immense traffic snarl around Mount Vernon that, aside from the inconvenience to everyday drivers, will have an estimated negative economic impact in the millions of dollars.
Imagine the impact to the South Sound if a similar incident occurred on the Nisqually River Bridge. Average daily traffic volumes are about 50 percent greater on the Nisqually bridge.
The Nisqually bridge is the same type as the one struck by an over-height truck, causing it to fall into the Skagit River. Both are what engineers call a through truss bridge, that rely on sway braces over the top of the bridge deck to keep the two side trusses stable.
It’s conceivable that a truck hitting the Nisqually bridge also could cause its collapse. If that happened at the peak of commuter rush hour, there’s a greater chance of damage and personal injury.
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Debbie Hersman, chair of the National Transportation Safety Board, said her agency will be looking for safety issues at other bridges. “The results can be very catastrophic,” she said.
Rerouting interstate traffic onto Old Highway 99 to Mounts Road would make commuting practically intolerable, and bring freight mobility to a near standstill. Drivers could conceivably drive through Shelton to rejoin I-5 at Tacoma. But that’s a longer and even more convoluted route, and crosses several other bridges, including the obsolete and narrow two-lane bridge at Purdy.
Similar aging bridges to the Nisqually and Skagit dot the I-5 corridor from Vancouver to Bellingham. Given the right circumstances, any one of them could collapse if hit in the wrong spot.
NTSB Chair Hersman characterized the Skagit disaster — fortunately, there was no loss of life — as a “wake-up call” to review the safety of the nation’s bridges.
We would extend that wake-up call to the Legislature, which at this moment is considering a comprehensive transportation package that would spend an obscenely small amount on preserving and maintaining our roads and bridges. Instead, it would spend billions on new projects.
State lawmakers may seize the timing of the Skagit bridge collapse to ask voters for a 10-cents-per-gallon gasoline tax. If so, they risk wasting a golden opportunity without major alterations to the House Transportation Plan under consideration.
Any package put to voters this year must focus primarily on upkeep of our state’s transportation infrastructure, especially the pavement and bridges along I-5.