The BART transbay tunnel will be closed for repairs August 1-2 and September 5-7, Labor Day weekend. BART will operate buses between the West Oakland and Embarcadero BART stations, but you should expect very slow traffic on the Bay Bridge while BART is shut down. There will be additional ferries between Jack London Square in Oakland and the Ferry Building in San Francisco while BART’s transbay tunnel is out of service, but if I were you, I wouldn’t go to San Francisco while BART is shut down unless you absolutely have to.