The fix is on. And this time bridge engineers simply don’t have the luxury of time when it comes to getting a pair of fixes in place at the now-collapsed Interstate 5 bridge over the Skagit River in northwest Washington.
Thursday there was an I-5 bridge, as one would expect on the main connector between Seattle and Canada (not to mention all those folks who live in the far Northwest corner of the state, such as me). Thursday evening it was gone.
After a Canadian semi-truck carrying an oversized load smashed against “critical steel supports” a northern section of the truss bridge buckled, crashing into the river and sending two vehicles in with it.
And how long I-5 remains void a bridge to carry 71,000 vehicles a day will certainly be up to how quickly bridge engineers, a state government, federal highway officials and contractors can get moving.
Already on Sunday the Washington State Dept. of Transportation announced plans for a temporary fix in working order within about three weeks—paid for 100 percent by federal emergency funds—and a permanent replacement set to slide into place sometime in fall, likely in late September. All things considered, those timetables would serve everyone well.
Work erecting two, 24-ft-wide temporary structures can already start, as plans include pre-building the spans and trucking them to the site, filling in the gap (only a section of the bridge fell and the majority of the 1,111-ft bridge left standing has been deemed suitable to continue).
The temporary four-lane bridge replacement will be a bit narrower and remain off-limits to oversized loads (especially ones so large they knock down the bridge in the first place) and can get installed once debris has been removed and underwater structural examination determine everything is set for the temporary span.
Crews will also immediately start work on a permanent bridge once the temporary one is in place. Temporary in-water piers will support a platform next to the gap and the bridge will slide into place once completed, hopefully in September.
Roughly 90 percent of the total $15 million bill should come from federal emergency funding.
“The home stretch will be a two week total closure of I-5 likely in September as crews remove the temporary structure and move the permanent bridge into place,” says Wash Dept. of Transportation secretary Lynn Peterson.
Two weeks now and two weeks then shouldn’t seem all that bad, especially when you see twisted steel sitting in a river.
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.