The latest phase of the Golden Gate Bridge's seismic retrofit — a process that began nearly 30 years ago — is about to begin, according to the Golden Gate Bridge, Highway and Transportation District.
Phase 3B is estimated at $879 million and will be funded using a combination of federal, state and district funds. It will take approximately six years to complete, with construction slated to begin in 2026.
Halmar International is heading the pre-construction as the construction manager/general contractor. The transportation district is expected to hire a construction contractor by year's end.
The seismic retrofit measures for these phases consist of strengthening foundations, the installation of micropiles and rock bolts, the construction of reinforced concrete shearwalls, the replacement of the housing roof/roadway deck with a pre-cast concrete slab-on-steel stringer deck system involving nighttime lane closures and other structural modifications.
The bridge is only approximately 6 miles from the San Andreas Fault, according to sfgate.com.
After the bridge was damaged in 1989 by the Loma Prieta earthquake, the transportation district determined that the bridge needed to be retrofitted to protect its structural integrity from future major earthquakes. That led to the Golden Gate Bridge Seismic Retrofit Construction Project, which continues to this day.
The first construction phases saw the district focus on strengthening the bridge's most vulnerable parts, which included the north approach viaduct, the south approach viaduct, the Fort Point arch and the south and north anchorage housings, sfgate.com reported.
The latest stage will include strengthening the suspension bridge and the two 746-ft. tall towers by adding steel plates. It also will reinforce the trusses and floor beams and install energy dissipation devices for shock absorption.
In addition, the south tower will receive a coat of its iconic orange paint and the existing lead paint will be abated, sfgate.com reported.
The total cost to finish the retrofit is expected to be approximately $1.8 billion, according to sfgate.com.
The district has said that it has secured nearly half the funding to begin. District spokesperson Paolo Cosulich-Schwartz told sfgate.com that the project's next phase is paid for by a $400 million federal grant, $200 million from Caltrans' Highway Bridge Program and $270 million from the district's reserves.
A final phase will retrofit the bridge's main 4,200-ft. long span.
