SAN FRANCISCO (CBS SF) – Bay Area Rapid Transit has deployed additional help to keep some of the busiest stations on the system clean.

According to a statement from BART, the agency has assigned special cleaning crews at the Civic Center, Embarcadero, Montgomery and Powell stations in Downtown San Francisco during the overnight hours.

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The special crews are in addition to workers that clean station entrances, crews who clean high areas that are hard to reach, and those who clean during the day.

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BART also said that it hired 15 “system service workers” who are assigned to clean stations last December. Most are cleaning stations in Downtown San Francisco, while others have been assigned to stations in Alameda and Contra Costa Counties.

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The agency described the work of cleaning stations in downtown as a “never-ending struggle,” with these stations being cleaned top to bottom every six weeks.