The shores of a key reservoir providing San Francisco's water burned relentlessly Wednesday as the giant, wind-whipped Rim fire extended its destructive march, UPI reported. The southern and western shores of Yosemite's 117 billion-gallon Hetch Hetchy Reservoir were ablaze, with ash falling on the reservoir's famously pure mountain water, which provides 85 percent of the city's supply and 2.6 million San Francisco Bay Area residents and businesses south to Silicon Valley. "It is an emergency," San Francisco Public Utilities Commission General Manager Harlan Kelly Jr. told the San Jose (Calif.) Mercury News. "We are taking it seriously," he said. "We are very concerned." The agency owns and operates the reservoir. By late Tuesday, the fire had scorched close to 190,000 acres -- or close to 300 square miles -- making it the seventh-largest wildfire in California history and the largest wildfire in the United States. Firefighters reported moderate progress in their battle, estimating the blaze was 20 percent contained, the same percentage as Monday. At least 31 residences and 80 other structures had burned. More than 4,500 residences remained threatened.
