A leaking dam that prompted evacuations in the Sierra foothills during an intense rainstorm last year has been repaired and is again storing drinking water for 2.7 million Bay Area residents, San Francisco water officials said Monday. The San Francisco Public Utilities Commission spent almost $22 million over the past year repairing and reinforcing Moccasin Dam in Tuolumne County. A storm in March sent a torrent of water and debris into the reservoir, raising fears the earthen barrier would collapse.