The temporary bridge for the Skagit River bridge on Interstate 5 sits at the ready, with cranes poised and parts getting assembled on the shore. Now all that Guy F. Atkinson Construction crews need is the okay from the National Transportation Safety Board—via Washington State Dept. of Transportation—to dive into the water and start erecting the Acrow-supplied bridge.
With Gov. Jay Inslee setting a “mid-June” target for having the temporary structure in place, crews have roughly two weeks to make that happen. But New Jersey-based Acrow already has nearly every temporary part on site in Mount Vernon, Wash., some brand new and some reused from a bridge in Hawaii. Thursday saw the arrival of some of the final pieces.
Atkinson, under an emergency contract, has been onsite performing the debris removal and will also construct this modern steel version of a Bailey bridge, two identical 160-ft-long spans, both 24-ft wide. A Bailey bridge was initially considered for the site, but Acrow’s version offers a wider model, able to accommodate four total lanes, the width of I-5 in that area.
Work will begin on placing the bridge in the hole left when the northernmost of four 58-year-old Warren through truss spans crumpled into the river on the evening of May 23, just over a week ago, when the NTSB releases the site to the state.
Currently, the 71,000 daily vehicles reroute through Burlington, Wash., and Mount Vernon, spread across two different, and much smaller, bridges that typically only serve local traffic.
While debris removal is nearly done, some pieces must be preserved for safety officials to inspect, first at a local staging area and then, possibly, at labs in Washington, D.C.
Final designs on what will likely be a steel girder permanent span to replace the temporary span haven’t been set, but the state still expects that bridge to be constructed on site and rolled into place, open to traffic in late September, if all goes well.
Federal emergency money will pay for 100% of the temporary fix and just over 90% of the permanent replacement. The total price tag should hover around $15 million.
The other three spans of the bridge will remain and there’s no money available to replace the entire bridge, instead of just one span, the state says. Emergency money simply returns a site back to its condition before the emergency.
Once traffic moves off city and county streets onto the temporary bridge, those streets will become eligible for additional emergency money to bring them back to the standards they were in before the detours.
To watch progress at the Skagit site, WSDOT has placed a webcam looking at the bridge. Check it out here.
Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He has also written for TIME, Popular Mechanics, Popular Science and more. You can follow him on Twitter at @tdnewcomb or visit his website here.