BART spent $90 million on new fare gates. They're recovering about $10 million a year in fares. That's a 9-year payback on paper. The actual return hit in six months. Embarcadero station went from 112 hours of corrective maintenance in the six months before installation to 2 hours after. Daly City saved 109. Balboa Park saved 75. Across the system, 961 hours of cleanup work disappeared. Corrective maintenance is the term BART uses for graffiti, heavy soiling, vandalism, the damage that needs…