With more than 2,000 mi. of shoreline, Puget Sound provides Seattle, Tacoma and the surrounding cities with the kind of deepwater access to the ocean found only rarely in the United States.
Huge ships can bring their cargo deep into the state, allowing for rapid distribution of goods to businesses and consumers.
The sound requires ships of all kinds and bridges to coexist with this massive waterway. The Interstate 5 Ship Canal Bridge is one of the many arteries that makes life in Seattle possible. The mile-long bridge carries some 240,000 vehicles each day over Portage Bay to Capitol Hill and the University District in Seattle.
The double-decker steel truss bridge carries eight lanes of divided traffic on the top deck with four lanes of one-way express of traffic on the bottom.
As part of the Revive I-5 program, the Washington Department of Transportation (WSDOT) is working with Atkinson Construction to make repairs on the bridge deck. Workers are scheduled to complete work on the northbound section this year. Project planners expect to complete the southbound work by the end of 2027.
The project will cost $178 million.
Tom Pearce, spokesperson for WSDOT, told Construction Equipment Guide of the need for such a project. “The bridge's last major preservation work was 40 years ago,” he said. “Workers will repair and resurface the upper bridge deck, replace concrete and aging bridge expansion joints and improve drainage issues.”
Because of the heavy traffic volume, even small repairs can cause backups. “Since 2019, our team has made more than 200 emergency repairs,” Pearce said. “That means closing lanes to do the repairs right away, even if it is just fixing a pothole. This work is important in reducing accidents.”
Workers are using diamond grinding and then hydro milling to expose the deck, then making the repairs with fresh concrete. Underneath the bridges, workers are wrapping the concrete fillets with carbon fiber to further prolong the life of the bridge. These fillets are between the top of the girder and the bottom of the bridge deck. The construction team will use about 4,000 cu. yds. of concrete for the project.
Workers will be using concrete on the bridge that has additives to improve strength and durability to bind the aggregates together. The construction team is using a diamond grinding milling machine to help remove some of the old deck.
The bridge towers some 160 ft. above the water, with 135 ft. of clearance for ships. The height meets Coast Guard requirements and allows large ships to pass safely beneath the structure.
“We take safety seriously and have installed scaffolding to protect workers and materials from falling into the water below,” Pearce said. “Our team has also put debris screens on the bridge and cloth screens that extend above sign barriers.”
WSDOT and Atkinson also have taken steps to handle traffic while at the same time keeping the workers safe. The plans call for a concrete barrier between lanes on the top level. Work will proceed in the right lanes, squeezing traffic down to two lanes on the other side of the barrier.
Although the plan will be difficult for commuters, Pearce is convinced it is the right step to get a rehabilitated bridge.
“Closing down two lanes is difficult, but other plans would require nearly 10 years,” he said. “This plan means the work will be done in just two years. Also, if there is a rain event, we can be back on the job the next day, rather than requiring us to close the work down for a whole weekend.”
