Structural damage caused by oversize truck loads to the thousands of overpasses on the country’s Interstate system is relatively rare, but each incident creates the potential for significant disruption to vehicle traffic as well as safety problems.
The incident in on southbound I-5 in Chehalis, Washington in 2016 was a textbook case.
A semi-trailer hauling an oversize load of a pair of excavators scraped along the underside of the I-5 Chamber of Commerce Way overpass in downtown Chehalis, causing a stream of debris on the highway that damaged two cars, sent one driver to the hospital and caused significant structural damage to the southbound portion of the bridge. Built in 1958, the overpass had been struck by trucks nine times in the past 10 years.
The Washington State Department of Transportation (WSDOT) closed the bridge – which is critical for easy access to both large and small retail businesses in Chehalis – soon after the crash in order to assess the structural integrity of the bridge. While the bridge seemed to be structurally sound under its own weight, four of the six girders supporting the bridge deck’s weight were irreparably damaged, and others showed signs of previous repairs from collision. As a result, WSDOT secured an emergency contract and quickly announced the overpass would be closed until the agency could repair the damage. Crews tore down the damaged span over southbound I-5 on July 26th, four days after the crash.
With the damaged third-span of the bridge deck removed, and the immediate safety concern taken care of, WSDOT staff began considering its options for restoring travel over the Interstate as quickly as possible. Governor Jay Inslee declared a state of emergency regarding the bridge, citing an estimated $6 million in damage to the structure.
It was determined that rebuilding the concrete bridge deck would take more than a year. And while the state Legislature has set aside $75 million to redo the Chamber Way Overpass and accompanying on and off ramps in preparation for the future addition of two lanes, funding for the design on the project isn’t authorized until at least 2019, with construction coming as late as 2023.
WSDOT decided to focus on quicker, more feasible options in the short-term, but first had to create a computer model of the bridge. After the model was developed, staff could begin to discuss short-term options. On July 29 it was announced that the best short-term alternative was to install a temporary modular Acrow bridge over the removed south span of the overpass, which would allow the bridge to be operational in as little as two weeks, using components from Acrow’s recently opened location in nearby Centralia, WA.
Acrow’s 50-foot modular structure was used to replace the removed span of 51’ 6” so it was necessary to retrofit the existing bridge to cover the extra foot and a half, and to account for the fact that the old bridge has six girders, and the Acrow Bridge two. The new deck also has a much higher clearance than the demolished bridge section. Chamber Way is marked at 14 feet, 8 inches, but the Acrow bridge is 16 feet above the road, the Federal Government standard for freeway overpasses. Acrow’s superstructure is rated for HL-93 loading.
The structure was re-opened on August 4, less than two weeks after the accident. “The response to reconnect people to a major Chehalis business hub in such a short amount of time is an impressive feat,” said Governor Inslee. “This accomplishment is truly a team effort, made possible by WSDOT’s dedicated staff, their contractor and their subcontractors. I also want to thank the public for their patience and understanding during the past two weeks.”
Speed is always a critical factor in emergency projects, but particularly so in situations involving Interstates. Acrow worked closely with WSDOT, Atkinson Construction, and Max J. Kuney to accelerate the installation. DOTs and contractors consistently turn to Acrow for quick turnarounds that minimize delay and facilitate on-time and ahead-of-time outcomes to complicated projects.
Acrow sold the materials used in this project to WSDOT, which the state will keep it as an asset for future use. Acrow also supplied temporary bridging to WSDOT during the construction of a four-lane,160-foot-long replacement span on one side of the Skagit River Bridge on I-5 in Mount Vernon, WA in May 2013 after it was hit by a semi-trailer carrying an oversize load and collapsed.
By Jack Arizcuren, Pacific States Sales Manager, Acrow Bridge