West Seattle Bridge to remain closed until 2022!
By Heidi Groover and Mike Lindblom of the Seattle Times
The West Seattle Bridge will remain closed to traffic at least until 2022 because of the prolonged efforts needed to first brace and then repair the cracking concrete main span, the city now predicts.
“It may not be possible to repair the bridge as it currently is,” Sam Zimbabwe, director of the Seattle Department of Transportation (SDOT), warned in a news conference Wednesday. “That may be because of the deterioration of the bridge, or the technical or financial feasibility of repair.”
Just to install bracing for the 590-foot long span, that arches 14o feet above the Duwamish Waterway, is estimated at $33 million — including related traffic control and maintenance on the lower-level swing bridge — and require the rest of this year, he said.
Zimbabwe couldn’t guess how much a full repair would cost, to give the bridge another 10 years of life.
And he said it’s too early to know whether the bridge, once reopened, could revert to its original six-lanes, or take heavy trucks and buses as before. That uncertainty creates a greater challenge for Seattle City Council members, who at a March 30 briefing hoped for some kind of near-term, interim repair that could allow at least some traffic to flow.
SDOT declared an emergency closure on March 23, after diagonal cracks grew two feet in two weeks — following other rapid growth since late 2018. Engineering consultants were beginning to worry that cracks on the walls, floor and ceilings of the hollow concrete girders would connect and create risk of collapse.
The bridge is the city’s busiest span, taking 100,000 vehicles and 25,000 transit riders daily on average before the coronavirus outbreak dramatically cut traffic. When the pandemic wanes and people resume work and leisure trips, the bridge will still be closed. Continued telecommuting, and many other changes in travel choices, will likely be needed.
Apparently no repairs would allow the bridge, which opened in 1984, to last for its entire 75-year design life, Zimbabwe said. Discussions need to start sooner than expected, on a long-term replacement plan, he said.
Meanwhile, SDOT pointed to another problem that must be fixed this year to keep the bridge stable long enough to repair the arched span. A bearing atop Pier 18, which supports the eastern side span at Harbor Island, is stuck in a way that resists normal thermal expansion, causing a shock that stresses the bridge, said Matt Donahue, SDOT roadway structures director.
The bridge has continued to crack since it was closed but at a slower rate, Donahue said. This validates SDOT’s decision, in conjunction with Mayor Jenny Durkan, to abruptly halt traffic, officials said.
Even amid the coronavirus outbreak, the closure has triggered occasional congestion on surface roads. Some drivers have ignored rules limiting the lower crossing to emergency vehicles, transit and freight, though police began to enforce the rule last week.
Detours can add up to five miles for some drivers who go south to the First Avenue South or South Park bridges.
“We understand the impacts this has had and will continue to have on the community, and we want to thank the West Seattle community for their understanding, their patience and their resilience overall,” said Zimbabwe, who moved to West Seattle last year from Washington, D.C. “We are working hard to help people get to where they want to go.”
The city noticed an unexpected spread of cracks in 2013, but rather than try costly repairs, chose to monitor them by attaching gauges, squirting epoxy into cracks, and conducting more frequent, yearly inspections, instead of the standard two-year interval.
The crack growth increased during 2018 and 2019. By February, engineering consultants proposed a reduction in traffic lanes and weights as cracks grew.
The cracks could be due to a number of factors, including concrete shrinking, the addition of a fourth eastbound lane often packed with vehicles, including buses weighing about 50,000 pounds. Two consultants have speculated that the 2001 Nisqually earthquake — which shook the bridge three inches according to SDOT inspection records — could have weakened it years earlier.
Heidi Groover:hgroover@seattletimes.com;Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com; on Twitter: @MikeLindblom. Staff reporter Mike Lindblom covers transportation for The Seattle Times.
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