Renton’s freeway overpass at Lind Avenue Southwest will be soon reduced to two lanes, followed by brief Interstate 405 closures in a couple months, after a tall truckload smacked several overpass girders Monday morning.

Washington State Patrol Trooper Rick Johnson said a truck pulling a backhoe struck the overpass 17 feet above the roadway.

“They basically just didn’t lower the boom enough, for whatever reason,” he said. “I’m assuming a citation will be issued.”

The Lind overpass is blocked, but in a few days the four-lane road will reopen with only two lanes until some girders supporting it can be replaced, said Washington State Department of Transportation spokesperson Tom Pearce. He said WSDOT needs to choose and deliver lightweight lane barriers, possibly water-filled barrels, instead of concrete Jersey dividers that would add stress known as “dead load” to the bridge.

As for I-405, no closures are planned for now, but in a few months there could be overnight southbound shutdowns to replace two or three girders, Pearce said. Schedules will hinge on a bidding process, but these aren’t considered emergency repairs, he said.

Midday inspections found “extensive damage” to three girders and minor impacts on two others, out of a total eight girders supporting the Lind Avenue roadway, Pearce said. Some of the internal steel cables, known as pre-stressed strands, are severed or bent, he said. Those cables strengthen the concrete girders lengthwise. 

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However, the entire freeway including onramps was expected to remain open through Monday evening’s commute and beyond.

“If we were to determine that a situation is unsafe, we would close the freeway,” Pearce said.

The I-405 roadway has a clearance of 16 feet, 4 inches beneath the Lind Avenue overpass, compared to a 14-foot legal truck height limit, said Tina Werner, a WSDOT maintenance communications specialist. The most recent routine inspection found at least two other locations above I-405 where truckloads hit girders and caused minor damage since 2008, she said.

Traffic slowed to a crawl for a time Monday morning while an inspection team blocked the onramp from Highway 167 to southbound I-405. But the ramp reopened by afternoon.

Besides girder strength, an equally important issue is preventing falling concrete pieces from hitting vehicles as they accelerate to 60 mph. WSDOT said workers scraped away loose materials during the inspections Monday.

That sort of cleanup, along with rust-proof repainting, was needed after the Stanford track team’s bus caught fire in January 2019 beneath the Interstate 5 Columbian Way overpass.

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In 2016, the state closed Front Street in Issaquah to replace an I-90 overpass girder that was damaged by a truck months before.

Standard freeway overpasses are 15 feet or higher, though in many locations, including Seattle’s University District, there are some lower clearances marked by yellow signs.

Under state law, truck owners are liable for damage to bridges, and can be pursued in civil court to repay WSDOT. Pearce said the state often seeks repayment, but didn’t have data immediately available.

Truck strikes happen occasionally all over the state. Last July, a tall load damaged the Highway 504 overpass above southbound I-5 in Toledo, south of Chehalis, which WSDOT said had been struck three times in five years.

The state’s most famous overheight crash was the I-5 Skagit River Bridge collapse in May 2013, which caused a deck span to drop into the river, and three vehicles along with it, though people avoided serious injuries. Afterward WSDOT sawed away low bridge-truss braces and raised the clearance to 18 feet.