The SFCTA is retrofitting eight seismically deficient bridge structures on Treasure Island Road to meet current safety standards. The $126 million project, part of a larger infrastructure improvement program, involves new retaining walls, roadways, and a retrofitted bridge. Completion is expected by late 2026, supporting increased residency, transit access, and economic redevelopment on Yerba Buena and Treasure Islands.
Photo courtesy of the San Francisco County Transportation Authority
Pillings are installed adjacent to the San Francisco Bay.
The San Francisco County Transportation Authority said it is on schedule to complete the $126 million West Side Bridges Retrofit project on Treasure Island Road by addressing eight existing bridge structures that are seismically deficient with new retaining walls, roadways and a retrofitted bridge to meet current safety standards.
Construction began in June 2023 on the structures, which are a crucial connection between Yerba Buena Island, Treasure Island and the Bay Bridge and will be completed by late 2026.
Photo courtesy of the San Francisco County Transportation Authority
This is one part of a larger multimodal infrastructure improvement program on the Islands, the other two completed being the I-80 East Side Ramps Project (2016) and the Yerba Buena Island/I-80 Southgate Road and Interchange Project (2023). The eight existing bridge structures are on the west side of Yerba Buena Island and comprise a viaduct along Treasure Island Road, just north of the San Francisco-Oakland Bay Bridge (SFOBB).
The project limit is approximately 2,000 ft. northward toward Macalla Road. The bridges were constructed between 1937 and 1964 and were determined to be seismically deficient so the Transportation Authority, in cooperation with the California Department of Transportation (Caltrans) and the Federal Highway Administration, is working to bring the bridge structures, retaining walls and roadways up to current seismic safety standards.
The project is funded using federal (Highway Bridge Program and Rebuilding American Infrastructure with Sustainability and Equity), Federal Congressionally Directed Spending, state (Proposition 1B) and local (Treasure Island Development Authority, Bay Area Toll Authority, Local Partnership Program and Proposition K Sales Tax) funds.
Construction consists of the following seismic retrofit strategy, which was determined to be the most cost-effective approach: demolishing seven bridge structures, realigning the roadway into the hillside, constructing six retaining walls and one undercrossing structure, and seismically retrofitting one bridge structure.
The project includes a bike path and will allow for the development of a dedicated transit-only ramp to the SFOBB, providing better transit access to the Islands' residents.
Photo courtesy of the San Francisco County Transportation Authority
"It's geared for increasing the durability and reliability of the roadways as Treasure Island continues to develop. The plan, from a housing perspective, is 8,000 additional residential units," said Carl Holmes, Transportation Authority's deputy director of capital projects. "We are working on the backbone infrastructure to support and be ready for the increased residency on the island."
This project will ensure the resiliency of transportation for Yerba Buena and Treasure Islands and provide unimpeded access to United States Coast Guard Sector facilities for homeland security. It also will improve roadway safety for drivers, transit users, pedestrians and cyclists on the island.
And it will support the ongoing economic redevelopment of Yerba Buena and Treasure Island that will transform the islands to a vibrant new neighborhood with 27 percent of the 8,000 units Holmes mentioned being affordable housing.
The project contract delivery method is construction manager/general contractor (CM/GC) with Golden State Bridge/Obayashi JV (GSB/O) chosen during a CM/GC selection process in 2018 to provide preconstruction services, including cost estimating, risk analysis and constructability review. After the completion of the final design in late 2022, an agreed price to perform construction was determined, and GSB/O was contracted to construct the project.
Key subcontractors include Farwest Safety; Crystal O'Neill Electric; Access Limited Construction; Chrisp Co.; Team EES; Coral Construction Co.; Bay Cities Paving and Grading; West Coast Drilling; Oliveira Fence; Dees-Hennessey; Silverado Contractors; and Gonsalves & Santucci. WSP is providing resident engineering/construction management, inspection services, construction staking and material testing services.
Specialty labor has included carpenters, pile drivers/drillers, laborers, ironworkers, operating engineers, electricians and Teamsters. Construction materials include 6,300 cu. yds. of structural concrete; 2,200,000 lbs. of reinforcing steel; 6,500 linear ft. of steel piling; and 9,600 linear ft. of drilled piling, along with specialty materials that includes 200 cu. yds. of shotcrete; 368 tiebacks/ground anchors each; and 11,600 linear ft. of soil nails. A variety of heavy construction equipment is being used including drill rigs, cranes, excavators, loaders, dozers, concrete pumps and trucks.
"What the CM/GC contract method did is allowed for us to engage with a general contractor while we were finalizing the design. The benefit is we were able to better ascertain some of the risks that the design may not have treated in the best way," Holmes said. "For example, when it came to some of the bridge demolition, looking at some of the risks and making sure it's done with a certain level of safety, productivity and speed. It's been a true collaboration."
The project now requires the full closure of Treasure Island Road until project completion in 2026. This allows for a more efficient and shorter construction duration. To facilitate local traffic, the Transportation Authority coordinated with local development teams to construct the Forest Road Detour, which provides full access from Treasure Island to Yerba Buena Island and the eastbound and westbound on ramps to the SFOBB. Upon completion of the project, Treasure Island Road will be reopened.
The project has witnessed some challenges with ground conditions when excavating for retaining walls, but soil boring tests completed earlier in the process helped anticipate the issue.
Photo courtesy of the San Francisco County Transportation Authority
Construction of retaining walls and the vehicular box culvert will continue over the next two years. Holmes also shared that local artist Muzae Sesay provided the design for a decorative retaining wall, adding a local arts touch to the project.
"We're actively in construction right now building retaining walls. We completed most, if not all, our bridge demolition. We have about a third of the island roadway closed but we have a detour that has been in place before we had the closure so there are ways to still traverse through the island," Holmes said.
"It's good that we were able to shut down a portion of the roadway because not having to worry about impacting the public is helpful. A significant amount of work is being performed on the steep hillsides of Yerba Buena Island. Access constraints and careful planning by the contractor to develop site access for the equipment to construct, material deliveries and worker safety has been key to successful construction to date." CEG
Ruksana Hussain
Ruksana Hussain is a Los Angeles, California-based award-winning journalist with 19 years' experience working with local, national and international print and digital media for consumer and trade markets. As a magazine editor and features writer, she covers a broad range of topics including construction and design, diversity and inclusion, data privacy and security, and more. She earned her bachelor's degree in sociology in India. Leisurely pursuits include traveling, random researching and attempting word puzzles of any nature.
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