The controversial proposal to allow riders to bring sealable coffee cups on BART trains soon will be pored over by the agency’s board of directors.

BART Director Lynette Sweet proposed allowing passengers to bring a so-called sippy cup onto the trains after the agency approved the addition of eight Peet’s Coffee and Tea kiosks at Bay Area stations.

BART’s general manager, Dorothy Dugger, opposes the idea, saying that the increased maintenance operations needed to address cleanliness issues will cost the district $6 million annually.

When the cup issue will be discussed has not been determined.