The Twin Peaks Tunnel has over a century of service under its belt and needs work to keep up with the demands of time and the Muni system. We conduct regular visual inspections and recently completed a comprehensive structural inspection of the tunnel. The inspection found that the tunnel is safe for both Muni passengers and workers, but two areas within the tunnel will require some immediate rehabilitation and repair work. We plan to complete these repairs this year over the summer.
After completing these repairs, the SFMTA will continue conducting regular inspections and structural evaluations of the tunnel, and expects to make additional improvements to the tunnel over the next 5-10 years to keep it safe and reliable for years to come.
Construction Timing
The work this summer requires three separate closures for the tunnel:
- June 22-23 (weekend)
- July 20-21 (weekend)
- August 22-29 (eight days, Thursday-Thursday)
We are doing everything we can to keep the shutdown durations short and will work closely with riders, merchants, and residents to minimize any disruptions. The weekend closures in June and July will allow us to conduct trials of the tunnel repairs, with full repairs to be completed during the eight-day closure in August. This closure also allows us to consolidate the repair work with needed track maintenance, completing multiple projects at once and minimizing construction impacts.
Additionally, the San Francisco Unified School District will begin an improvement project at the West Portal Elementary School, which sits on top of the Twin Peaks Tunnel. We are working closely with SFUSD to coordinate work on the tunnel with their project schedule.
Service Impacts
During construction, the subway will operate from Embarcadero to Castro, and we will run bus shuttles from Castro and Church to the outer rail terminals on the K, L, and M.
- West Portal and Forest Hill stations will be closed all day. Please use K, L or M bus shuttle substitutions on the surface.
- M Buses and K Buses will run between Balboa Park and Church, with stops at West Portal, Forest Hill, Castro and Church.
- L Buses will be extended to run between SF Zoo and Church, with stops at West Portal, Forest Hill, Castro and Church.
- S Shuttle trains will run special service between Castro and Embarcadero stations, serving all stations in between.
- J, N and T trains will run as usual. Transfer between underground Muni Metro trains and K, L and M buses at Church or Castro.
Construction Details
Grout will be injected to strengthen loose soil adjacent to the tunnel in two areas. Steel reinforcements within the tunnel walls in these areas will also be retrofitted with new steel tie-rods. Planned track maintenance work includes replacement of rail joints in the eastern part of the tunnel near the Eureka Valley station area of the tunnel.
After completing the work, we'll continue to inspect and monitor the tunnel, and longer-term rehabilitation work will be planned based on those findings.
