The Seattle Department of Transportation (SDOT) has begun recruiting construction firms to strengthen the cracked West Seattle Bridge, to be reopened for traffic in mid-2022.
City engineers estimate the contract value at $48 million in bid documents posted Wednesday morning. The winning team will write a final engineering design and hire subcontractors before work on the concrete structure resumes in November.
The bid kickoff comes as Seattle approaches the anniversary of the six-lane span’s March 23 emergency closure, when bridge engineers concluded that accelerating cracks might lead to a collapse if traffic continued. The damage began as tiny hairline cracks seven years earlier, and the city didn’t perceive them as a safety threat until early 2020.
Over next winter, contractors will string tons of steel rope lengthwise through the 140-foot-high central span, and the two adjacent side spans, to compress and fortify the 37-year-old concrete, a process known as post-tensioning.
SDOT says it has reached 30% design, a common public-works project milestone. Under a relatively new contracting method, the winning team will finish full engineering, then propose a price to complete repairs. That’s supposed to help the city and builders find possible problems before heavy construction begins, reducing expensive change orders.
Crews also will inject grout to strengthen the soil around Pier 18, a foundation on the east end. This will improve the bridge’s ability to withstand an earthquake, said Heather Marx, city mobility director.
The new contractor also will apply carbon-fiber wrapping to reinforce the lower Spokane Street swing bridge, which has less-severe structural cracks and passed a heavy-load test in Spring 2020. That crossing is now taking added punishment by detoured transit buses, and it soon will absorb hundreds of truck trips when the Port of Seattle’s giant Terminal 5 reopens just west of Duwamish Waterway.
The lower bridge may also need repairs to the pivoting lock systems that control the pivoting twin bridge spans when boats pass through.
After the high-rise repairs are done, by June 2022, traffic would be reintroduced gradually as SDOT watches how the bridge responds, Marx said.
It’s possible repair jobs on the swing bridge will result in both bridges being closed at the same time. Even trucks and buses would need to take the five-mile detour around. However, SDOT expects those full corridor closures will be limited to certain weekends and holidays, Marx said.
Before the shutdown, the high bridge served more than 100,000 vehicles and 20,000 transit riders daily, as the busiest city-owned crossing.
Most travelers must detour as far as five miles, through industrial and residential streets. The low swing bridge is limited to transit, freight trucks, emergency vehicles, and a small number of pass-holders, such as maritime workers.
Since camera enforcement began in January, daily crossings have decreased by more than 2,000 vehicles on the swing bridge.
Diane Sosne, president of Service Employees International Union Healthcare Local 1199NW, suggests more passes, such as for on-call nurses who need to reach work within 30 minutes — one of many pass requests from the community. SDOT expects port truck traffic early next year to fill the low bridge and is reluctant to loosen the access rules now.
SDOT’s overall budget is $175 million for work associated with the West Seattle Bridge corridor. That includes not only the repair contract and contingencies, but also last year’s bridge stabilization, engineering to study the bridge and a future replacement bridge, pavement repairs and new traffic signals in the detour routes, and nondriving alternatives.
Marx said the city has identified $124 million that will be repaid by future real estate taxes, along with a $15.9 million federal grant and $9 million from a voter-approved transit sales tax. State lawmakers are considering a $25 million contribution if a huge transportation package passes in Olympia.