Voters approved the project in 2003, to replace a freeway damaged in the 1989 Loma Prieta earthquake. Back then, the cost was $647 million. Today, the price tag is $1.6 billion, with the lion's share of the funding still to come from the federal government. In July, San Francisco's Civil Grand Jury concluded the project was poorly designed, won't meet projected ridership levels, and, as the scathing title of its report says, costs "too much money for too little benefit." At about $1 billion per mile, the Central Subway has become a driving force in Tuesday's mayoral election.