Caltrain weekend service to SF cut for 6 months during construction

Odalys Vallejo is silhouetted against a train at the CalTrain Station near 4th and King streets in San Francisco, Calif. Wednesday, Aug. 29, 2018. Odalys Vallejo is silhouetted against a train at the CalTrain Station near 4th and King streets in San Francisco, Calif. Wednesday, Aug. 29, 2018. Photo: Jessica Christian / The Chronicle Buy photo Photo: Jessica Christian / The Chronicle Image 1 of / 13 Caption Close Caltrain weekend service to SF cut for 6 months during construction 1 / 13 Back to Gallery

Weekend Caltrain riders won’t be able to ride the train to or from San Francisco starting Oct. 6 for about six months.

The 22nd Street station and the San Francisco terminal on Fourth Street will be closed to accommodate construction. Instead, riders can take a free bus to connect to and from those stations and the Bayshore station on the border of San Francisco and Brisbane, which will be the end of the line for weekend rail service. The bus rides will be free but are expected to add 10 to 20 minutes to each trip.

The commuter railroad, which carries about 23,500 passengers on weekends, is stopping short for about half a year to make room for construction crews that will be working to prepare tunnels for electrification.

Caltrain is in the middle of a $2 billion modernization project that will convert the diesel trains to an electrical railroad. During the partial closure, crews will prepare four tunnels to carry electric trains. They’ll install the overhead equipment that will deliver power to trains and slightly widen the tunnels. They’ll also take advantage of the closure to work on drainage.

Dan Lieberman, a Caltrain spokesman, said the railroad opted for the weekend closures because they would inconvenience the fewest riders and create the most time for construction crews to work.

“There is no good time to close Caltrain,” he said, “but we are aiming to have this done before the Giants season begins.”

The Giants’ home opener at AT&T Park, a short walk from the Caltrain terminal, is April 5 against Tampa Bay.

Caltrain has changed its online schedules to include the extra travel time added by the bus connections. Plans call for crews to conclude work in time for regular Monday morning service, but Lieberman admits there’s a chance work could affect early Monday travel.

“We don’t think that will happen, but if it does, we will let people know,” he said, advising early morning riders to check the Caltrain website or Twitter.

Regular weekend service will be restored on Jan. 5-6 to accommodate events surrounding the NCAA college football playoff national championship at Levi’s Stadium on Jan. 7.

Fans of Caltrain’s traditional Holiday Train, which features a train festooned with colored lights, shouldn’t despair. The show will go on Dec. 1 and 2, Lieberman said, with trains traveling around construction.

Michael Cabanatuan is a San Francisco Chronicle staff writer. Email: mcabanatuan@sfchronicle.com