Fire officials say crews are finally gaining ground on a massive wildfire burning near Yosemite National Park and they expect no water or power disruptions from ash raining on the main reservoir that supplies San Francisco.
Glen Stratton, an operations chief on the fire suppression team, said Monday night that while the blaze continues to grow in size, containment numbers are up, as is optimism that crews are making progress.
The fire is 20 per cent contained, up from seven per cent on Monday. Flames have charred more than 650 square kilometres of brush and timber and 88 square kilometres of that is inside the park.
Nearly 3,700 firefighters are battling the biggest wildfire on record in California's Sierra Nevada. Rugged terrain, strong winds and bone-dry conditions have hampered firefighters' efforts to contain the blaze, which began Aug. 17. The cause has not been determined
"It's been a real tiger," said Lee Bentley, fire spokesman for the U.S. Forest Service. "He's been going around trying to bite its own tail, and it won't let go but we'll get there."
- California's Yosemite wildfire in eyewitness photos
San Francisco gets 85 per cent of its water from the imperilled Hetch Hetchy reservoir as well as power for municipal buildings, the international airport and San Francisco General Hospital. The threat to the city's utilities prompted Gov. Jerry Brown to declare a state of emergency for San Francisco.
Utility officials monitored the clarity of the water and used a massive new $4.6-billion gravity-operated pipeline system to move water quickly to reservoirs closer to the big city.
"It looks great out there," Stratton said Monday night. "I don't think we're going to have any problems up at Hetch Hetchy."
So far the ash that has been raining onto the reservoir has not sunk as far as the intake valves, which are about halfway down the 100-metre O'Shaughnessy Dam. Utility officials said that the ash is non-toxic but that the city will begin filtering water for customers if problems are detected. That could cost more.
Power generation at the reservoir was shut down last week so that firefighters would not be imperilled by live wires. San Francisco is buying replacement power from other sources to run City Hall and other municipal buildings.
It has been at least 17 years since fire ravaged the northernmost stretch of Yosemite that is under siege.
Weather conditions forecast for Wednesday may bring challenges in the morning as heavy smoke settles low to the ground, limiting visibility, but higher humidity was expected in the afternoon which could help dampen the flames, said Matt Mehle, a National Weather Service meteorologist assigned to the fire.