Water leakage closed portions of SF’s Chinatown subway station

The San Francisco Municipal Transportation Agency closed the main stair well and part of the platform at Chinatown-Rose Pak subway station because of a water leak on Thursday. The leak will take upwards of six months to permanently fix, the agency said. 

The leak occurred over the main stairwell leading to the platform, SFMTA’s chief spokesperson Stephen Chun told SFGATE. The stairs remain closed to prevent people from slipping on them. 

Water is leaking through the water-proofing membrane behind the structural shell of the cavern that houses the station, Chun said. The water-proofing system covers the entire underground cavern, which sits nearly 100 feet below street level, and is unique to the Chinatown-Rose Pak station. The massive underground structure is submersible and designed to operate while water flows over it. 

“The key is preventing or minimizing the amount of water that has penetrated the membrane,” Chun said.

It will take at least half a year to fix this particular leak. The solution involves injecting cement-like material behind the cavern’s structural shell, along with additional grouting measures, according to Chun.

“It will take time and effort to fill voids with grout and isolate areas that are leaking until we can finally plug them,” Chun said. 

Temporary measures will be in place for the next several days to divert water away from areas that civilians occupy, he added. 

San Francisco’s Central Subway Muni Metro line, which stops at Chinatown-Rose Pak station, opened for free weekend service as part of a “soft launch” last November before officially opening for daily service in January. Water drainage issues along the line were noted when riders first rode it in November: one rider noticed that red solo cups had been used to mitigate water flow over the tracks at Union Square/Market Street station on the day of the Central Subway line’s soft launch. 

“While it is unfortunate that we are experiencing the water intrusion problem, we need to keep in mind that the waterproofing system covers an enormous cavern deep underground,” Chun said.