Powell Street Station flooding causes BART commute delays in SF

A sign for BART's Powell station is seen on Friday, Nov. 6, 2015 in San Francisco, Calif. A sign for BART's Powell station is seen on Friday, Nov. 6, 2015 in San Francisco, Calif. Photo: Nathaniel Y. Downes, The Chronicle Photo: Nathaniel Y. Downes, The Chronicle Image 1 of / 1 Caption Close Powell Street Station flooding causes BART commute delays in SF 1 / 1 Back to Gallery

Flooding at BART’s Powell Street Station in downtown San Francisco caused lengthy delays running in the East Bay direction during the Monday evening commute, according to the transit agency.

It was not immediately clear what caused the flooding or what area of the station was flooded —and how deep.

Though it has not rained in the city as of late, groundwater constantly courses through the area around the station, beneath the sidewalks and streets. It’s caused minor flooding at the station before.

The ground water can overwhelm drainage systems in the station’s tunnels when it gets especially saturated, a spokesman said.

The delays impacted trains running from San Francisco to the East Bay.

BART initially reported the delays, which ran for 20 minutes, on Twitter before 6 p.m., and trains were recovering from the delays that dissipated later in the evening, a spokesman said.

Michael Bodley is a San Francisco Chronicle staff writer. Email: mbodley@sfchronicle.com. Twitter: @michael_bodley