While repairs buy time, Seattle closes in on options to replace West Seattle Bridge

The Seattle Department of Transportation hopes to complete its repairs to the West Seattle Bridge by mid-2022, which will end a nearly two-year closure that began when workers discovered cracks in the span during a routine inspection. While that repair will buy valuable time for the 37-year-old bridge, SDOT has acknowledged that it will eventually need to be fully replaced.

West Seattle High-Rise Bridge clears major hurdle on road to repair

“We estimate that the repaired high bridge will last approximately 40 more years,” SDOT said in a recent blog post.

While the city was evaluating whether to either repair or replace the bridge following its closure in 2020, it gathered research into what a replacement option could potentially look like. In the end, it looked into five concepts. That included a bridge situated north of where the current West Seattle Bridge sits, one positioned south of the current span, one that would be built “on-line” in the same spot as the original bridge, an underground tunnel, and a hybrid option combining the north and on-line concepts.

The goals in evaluating each choice were: to maintain existing on- and off-ramp connections; to keep the bridge at a similar width as its predecessor; to keep the same horizontal and vertical clearances for boat traffic under the bridge; and to use the most “cost effective” demolition and construction methods with the least possible impact to the surrounding neighborhood.

Ultimately, SDOT whittled the list down, landing on the “on-line” and the hybrid options as the designs that checked the most boxes.

History of the West Seattle Bridge

The north and south options were found to not “offer mobility benefits that offset their higher impacts and construction duration,” while the tunnel concept posed “significant challenges” in terms of mobility and impact.

Moving forward, SDOT intends to finalize these findings, with plans to come back to them in the future.

“In the coming years, we will revisit the study and further refine the design of the future replacement bridge,” SDOT described. “This could include the type and size of the bridge, pedestrian and bicycle access, how construction would be timed and what foundation and seismic requirements the bridge would have.”

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