Caltrans has spent over $500,000, perhaps close to $1 million, spreading the word that the Bay Bridge will be closed during the upcoming Labor Day weekend. A major connector between Oakland and San Francisco, the double-decker bridge’s seismic retrofit projects began after an extensive study following the 1989 earthquake, when a section of the upper deck collapsed. This weekend the Yerba Buena viaduct, a 350-foot-long, 90-foot-wide section, will be demolished and replaced. This task, daunting enough without the 81 hour time restriction, has been planned for maximum efficiency. Concrete-saws will divide the viaduct into 63 pieces. A crane will lift the pieces onto trailers, with trucks standing by to tow them away immediately. The replacement viaduct will be pushed into place with a roller system. And with luck all will be ready for Tuesday morning’s busy commute.