SEATTLE — Seattle Mayor Jenny Durkan on Thursday declared the West Seattle Bridge closure a civil emergency, a move city officials say is the first ever related to a piece of infrastructure.
At the same time, an expert review panel kept on the table the possibility of repairing the cracked structure.
The Technical Advisory Panel summed up its findings: “The TAP has not been presented with any information that indicates that a long-term repair is infeasible or economically unviable. We therefore recommend that this option be retained and fully explored.”
The findings support the Seattle Department of Transportation’s earlier assessment that a repair is possible.
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Some city officials are asking if repairing the bridge is the best move.
SDOT will now begin a detailed cost-benefit analysis of different options, including repairing, replacing or building a tunnel beneath the Duwamish River.
SDOT Director Sam Zimbabwe said in a KIRO 7 interview Thursday morning that the city could identify a preferred alternative in mid-Fall, likely in November.
At that time, city officials would have more information about the timeline and costs, which Zimbabwe said could be in the hundreds of millions of dollars.
Zimbabwe said the city is still working on the assumption that a bridge repair might only last a decade, and a long-term replacement still would be needed.
But, he added, "some of those engineering assumptions can continue to evolve."
City officials said Thursday's civil emergency declaration will strengthen funding options and provide more flexibility through streamlined permitting and contracts.
SDOT officials said they are seeking funding from state and federal governments, and are talking with Sound Transit, which is also reviewing options for a Duwamish River crossing for a new light rail line.
City leaders said they are taking seriously a proposal by retired civil engineer Bob Ortblad for an immersed tube tunnel placed in a dredged river crossing.
"Basically it's like laying a road in the bottom of the river," Ortblad said. "Structurally, it's much simpler."
An immersed tube tunnel would be very different than the deep-bore State Route 99 tunnel project that ran into trouble during construction.
Ortblad proposes a submerged pre-cast concrete structure.
“It’s such a short crossing. It’s only 500 feet across; it’s 30 feet deep. They’ve done these things all over the world,” he said.