District 1 City Councilmember Lisa Herbold shared some additional information regarding the start of work on the final stage of work on the West Seattle Bridge that was announced last Monday.

Below is a graphic showing the locations and type of repair work that will be done. It’s listed as “Phase 2 Rehabilitation.” The work already done to stabilize the bridge is list as “Phase 1.”

The “Phase 2” repair work will include carbon fiber wrapping and post-tensioning on the center span, but also on the other two sections of the bridge, between Piers 15 and 16, and Piers 17 and 18. “Phase 1” Stabilization work done last year was limited to the center span.  The exception was a bearing on Pier 18 that required releasing and replacing.

Post-tensioning involves tightening high-strength steel cables into the concrete girder to support the concrete. Some cables were included in the original bridge; some were added during stabilization, and more will be added in the repair.

Carbon-fiber wrapping strengthens the bridge, in tandem with the steel cables. It will be added both inside and outside the bridge. SDOT notes carbon-fiber wrapping is added in stages, alternating with post-tensioning, to ensure the bridge continues to strengthen as the girders get more compressed.

Additional visuals and details on post-tensioning and carbon fiber wrapping are available at the project website.

The website notes additional maintenance work that will be done, including paving:

While the final West Seattle Bridge repairs are underway, we’re also planning additional maintenance work on the entire West Seattle Bridge corridor from the connection at I-5 to Fauntleroy Blvd.

These improvements include:

• Replacing bridge joints that allow the structures to expand and contract during hot and cold weather safely
• Paving to give people driving a smooth and predictable surface that will last for years
• Replacing all signs and the structures that hold them with signs that are easier for people driving to read and withstand high winds and storms

Performing major maintenance work now – while the bridge is closed – is smart use of the contractor teams and we’ve sequenced the work, so it won’t affect the schedule of returning traffic to the bridge or lead to construction delays or detours for people driving and transit once we’ve reopened it to traffic.

The Council recently adopted the 2022 City budget; it includes funding for the bridge repair. The Council voted to authorize $44.6 million in bonds in 2022 for the bridge repair and related work. In addition, the Council separately authorized a $100 million for bond sale for bridge maintenance and rehabilitation that Councilmember Pedersen sponsored, and I co-sponsored.

This Council Budget Action, in addition to authorizing a bond sale, also provided $1.1 million in funding to “allow SDOT to advance project development to the 90 percent design stage for the following bridge rehabilitation projects: (1) $300,000 for Spokane Street Swing Bridge Hydraulic Overhaul (2) $900,000 for Spokane Viaduct Rehabilitation.”

Completing 90 percent design for these projects will allow SDOT to pursue construction funding through state and federal grant programs, or for consideration in the development of a future transportation levy proposal.