Multiple options offered on repair or replace of West Seattle Bridge; No full travel capacity till at latest 2026, no ITT tunnel being studied
In the fifth meeting of the West Seattle Bridge Community Task Force with the Seattle Department of Transportation six possible directions were presented to either repair or replace the damaged structure.
None of the options presented would restore full travel capacity until 2026, though some repair scenarios could put some traffic on the bridge by 2022.
SDOT in the the process of doing a Cost-Benefit Analysis (CBA) of the various options looking at the costs and attributes to make the best choice. The options presented on July 22 are meant to be reviewed by the Task Force, input taken from them and the Technical Advisory Panel on Aug. 5 then over the next couple of months the deliverables (basis, evaluation criteria, alternative design ideas, cost estimates and more) will be in hand by October.
This is all based on the assumption SDOT said that repairs are technically feasible. Notably SDOT did not include an Immersed Tube Tunnel (ITT) option to the north of the two existing bridges, opting to thus far not include that potential to instead put it in the same footprint as the existing bridge, thus delaying any possible early start should they make that choice.
In their presentation they stated:
Only a qualitative analysis will be performed for replacement alternatives for different alignment or structures (including a bridge or tunnel)
•IF we decide to replace, we will perform a Type, Size & Location (TS&L) study and deeper analysis to further examine multiple replacement alternatives, including tunnel and bridge options outside the current bridge’s footprint
•Based on the TS&L study, we will present a number of alternatives so we can reach the best option for a replacement
•We will then begin design work on the preferred alternative
In the CBA framework SDOT said that temporary shoring, or more extensive repairs or even a partial superstructure replacement with foundation strengthening could get some traffic flowing again by 2022 and last between 3 to 50 years depending the on the extent of the repairs.
A full superstructure replacement might get traffic going by 2025 but with a limited lifespan of between 50 to 75 years. A full bridge replacement would not make traffic restoration possible until 2026.
They said the tunnel (in the same footprint) requiring a tunnel boring machine and a 250 foot deep tunnel would also not allow traffic until 2026 but incorrectly claim the tunnel would only have the same length of service as the bridge. Tunnel longevity can approach 150 years.
Here are the options under consideration:
Proposed Evaluation Criteria
• Constructability Will the contractor be able to build the bridge given site constraints and schedule?
• Environmental What kind of temporary and permanent impacts will the bridge have on the Duwamish River and surrounding area? Can we build it within the mandated in-water work windows?
• Equity Will underrepresented communities be positively or negatively impacted by the preferred alternative?
• Forward compatibility Can it accommodate Sound Transit light rail?
• Funding Is the preferred alternative eligible for federal, state, local, or emergency funding?
• Maintenance, inspection & operation needs What will the preferred alternative need over its lifespan in terms of maintenance and inspection?
•Mobility Does the preferred alternative facilitate or hinder the movement of people and goods? How will it impact current local and regional traffic?
• Multimodality Will the preferred alternative accommodate multiple modes of transportation, including transit, pedestrian, and vehicle traffic?
• Regional business How will the preferred alternative impact regional and local businesses as pertains to the movement of people and goods and overall access? Will it impact the ship channel? Will construction affect business access?
• Safety/seismic What seismic standards will the preferred alternative have to meet?
Duwamish River Bridge repair program, Seattle Transportation Benefit District, low bridge access and health, Metro's efforts and SDOT Survey reviewed
The meeting also covered the ongoing repair efforts to the Duwamish River Bridge (1st Ave South Bridge), The Seattle Transportation Benefit District, low bridge access policy including a new placard to be displayed by permitted vehicles, King County Metro's efforts to get people around in the wake of the bridge closure, and SDOT's Reconnect West Seattle outreach efforts.
RECONNECT WEST SEATTLE UPDATE
SDOT said they got 10,430 survey results thus far in their Reconnect West Seattle effort and 1,035 Neighborhood Prioritization Ballots. SDOT's Heather Marx called this "An amazing response rate," The surveys, whose purpose is to collect data from the community about possible preferred travel options will close on July 31. On August 5th and 19th the Community Task Force will review the results and give input to SDOT with the formal Reconnect West Seattle Plan to be issued in September.
King County Metro Bridge Closure Response
King County Metro has been hard at work looking at how to get people around and presented their response to the problems travelers faces without the bridge. Steve Crosely, project lead covered what Metro called High Impact Mobility Improvements such as:
• Upgrade Water Taxi service to two boats up to all-day and year round
• Route 773/775 Water Taxi shuttle improvements and/or new third route
• RapidRide C Line service frequency upgrades (peak, off-peak)
• Robust bus service between Admiral and Downtown
• Route 50 service frequency upgrades to SODO Link Station
Noting though that 3rd party funding would be needed, but could be implemented quickly (no new capital needs).
They are currently running at around 25% capacity allowing for physical distancing.
Metro is bringing back multiple routes long time Metro users will remember including Route 55 and upgrades to the Water Taxi and shuttle improvements to Water Taxi shuttle routes. They are picking up more service between the Admiral Junction and downtown. An RFQ has been put out by Metro for another dock in downtown and they are looking at responses regarding that option. The Seacrest dock can accommodate two boats and at peak can run 2500 people an hour.