Dive inside the decrepit Twin Peaks Tunnel

Attention, Muni subway passengers.

The San Francisco Municipal Transportation Agency has finalized a start and end date for a two-month closure of the 100-year-old Twin Peaks Tunnel so crews can begin much-needed improvements inside the tunnel. The closure will begin on June 25 and end on Aug. 24.

There will be no train service running on the K-Ingleside, L-Taraval and M-Ocean View inside the subway as crews work between the West Portal and Forest Hill stations to replace rail tracks, make improvements to the drainage system, and make seismic upgrades inside the tunnel, including within the old Eureka Valley Station.

During the two-month closure, the transit agency will run bus shuttle buses on the K, L, M where passengers can either transfer at Castro or Church stations to make a connection to a shuttle train heading downtown.

The K will run trains between St. Francis Circle and Balboa Park BART Station while making its regular transit stops. The SFMTA is encouraging passengers on the K  to take BART if they are heading to downtown.

A Forest Hill shuttle bus will connect passengers to West Portal and to the L and M shuttle buses or K trains.

Muni passengers got a taste of the bus shuttle plan over the Memorial Day weekend. The transit agency closed the Twin Peaks Tunnel over the three-day weekend holiday so crews could prepare for the longer two-month closure.

John Haley, SFMTA director of transit, gave a few reporters a tour of construction crews working inside the old Eureka Valley Station — now just called the Eureka Valley portal. The portal is now mostly used to bring in equipment, said Haley.

Haley said the Twin Peaks Tunnel project will address travel time issues and bottlenecks in the subway.

Muni trains currently travel at 40 miles per hour in the Twin Peaks tunnel, even though the system is designed for trains to run at 50 miles per hour.

Haley said if trains travel now at 50 miles per hour, it could make for an uncomfortable ride for Muni passengers due to the current state of the rail track conditions.

Trains could run at 50 miles per hour once crews install the new rail tracks and the SFMTA makes an evaluation, Haley said.

The project also calls for crews to install additional crossover tracks at West Portal, which will allow more flexibility to move trains during subway delays or emergencies.

Haley said there is currently only one crossover track at West Portal:

“West Portal is the biggest bottleneck operationally in the system.”

There will be tweaks to the bus shuttle plan during the two-month closure.

Haley said the transit agency learned a lot from customer feedback and observations during the Memorial Day weekend closure:

“What we’re trying to do is make sure that we provide reliable, predictable, safe, alternative service.”

One change is that shuttle buses will both stop at Castro and Church stations. During the weekend closure, the L buses only stopped at Castro, and the K and M buses stopped at Church.

Haley said he appreciated the patience of Muni passengers:

“Our riders are smart. They follow us closely and I think they understand that we need to do this.”

Muni passengers can learn more about the project, summer closure and bus shuttle plan on the SFMTA website.