Design teams prepare for possible tunnel to replace Seattle bridge

10 June 2020

Seattle Department of Transportation (SDOT) is finally including the possibility of a tunnel to replace the rapidly deteriorating West Seattle High-Rise Bridge which is showing exponential cracking growth. Earlier this month, SDOT made an addendum to its original Request for Qualifications (RFQ) for the bridge’s replacement that allowed for ‘other replacement alternatives’.

The former bias in favour of a bridge replacement and for companies applying to have ‘ten years of bridge-building experience’ was revised, mainly due to the efforts of retired civil engineer Bob Ortblad. His persistence to amend the RFQ has generated substantial support in favour of a light rail tunnel and immersed tube solution under the river.

As a result, the new addendum allows for ‘other replacement alternatives to be evaluated as part of the contract’, and ‘will include but may not be limited to tunnel and Sound Transit coordinated options’.

SDOT is currently stabilising the cracking with ongoing repairs, including fixing bearings to one of the piers and constructing shoring support structures. But it is uncertain whether the programme will be feasible either technically or financially, and concedes that a replacement crossing will eventually be necessary. The bridge, which is currently closed at least until 2022, opened in 1984.