Repair Work To Close Twin Peaks Tunnel For 8 Days

K Ingleside and M Ocean View passengers will have to take shuttle buses for eight days in August when the tunnel undergoes significant repairs.

Workers inspect streetcar tunnel.
Workers inspect the Twin Peaks Tunnel, which first opened in 1918. | Courtesy SFMTA

The San Francisco Municipal Transportation Agency is planning maintenance work on the ceiling in the 106-year-old Twin Peaks Tunnel that will require an eight-day closure in August.

Director of Transit Julie Kirschbaum said at Tuesday’s SFMTA Board of Directors meeting that the closure will require K Ingleside and M Ocean View passengers to take shuttle buses. The transportation agency said K and M shuttle buses will run from Castro station to their westbound routes to Balboa Park. The closure will not affect service on the J Church, N Judah and T Third Street rail lines.

Rail service will continue to run between Embarcadero and Castro stations, the SFMTA said.

The critical work comes after the agency recently completed its most comprehensive report of the tunnel since the 1970s. The report by the engineering firm HNTB found distortion in the tunnel that has led to other issues in the tunnel, including fractured rebars, leaks and misaligned hangar rods.

Additionally, the report identified other problems including issues with leakage and drainage. Photos in the report showed a heavy buildup of efflorescence or crystalline deposit of salts in the tunnel. Photos also showed issues with the drains in the tunnel, including broken and clogged drains.

“I am pleased to report that there are no imminent safety hazards that were found, and the tunnel remains safe for our riders and our workers,” Kirschbaum told directors. “The inspection also identified some necessary repair work to ensure that it continues to stay safe.”

Over the summer, crews will work on installing tie rods in two locations to strengthen the ceiling, fill areas with grout behind the tunneling lining where there is loose soil or missing, clean out drains and strengthen or replace hangers. Crews will also be doing work to reinforce the crown of the tunnel.

The transportation agency has not yet finalized dates on when the closure will occur in August, but Kirschbaum said the agency is coordinating with another major construction project happening at West Portal Elementary School, just above the Twin Peaks Tunnel. The school is building two new buildings with construction beginning in the fall of this year, according to an April project update from the San Francisco Unified School District.

Transit officials said the tunnel will need more maintenance work over the next five to 10 years.

“This work will allow us to pace our improvements over a five to 10-year period, which aligns with our service needs, and also what we can afford," Kirschbaum said.

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