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Rim Fire Extends Further Into Yosemite
The wildfire raging in California's Yosemite National Park is expected to advance further into the park, as it continues to threaten a reservoir that supplies most of San Francisco's water.
The so-called Rim Fire has charred more than 160,000 acres - an area larger than the size of Chicago - in the northwest part of the national park.
Most of the damaged area is in the Stanislaus National Forest, west of the national park. In total 250 square miles have been affected.
But the blaze was expected to move east overnight and push deeper into Yosemite, as well as in areas to the north, US Forest Service (USFS) spokesman Trevor Augustino said.
Mr Augustino said that on Monday the blaze "made a good run to the park" and was 20% contained - up from 15% earlier in the day.
However, Tuesday's weather was expected to remain hot with temperatures in the low 30s Celsius (high 80s to low 90s Fahrenheit) with winds of 10 to 15 mph from the southwest.
On Monday the eastern flank of the fire burned to within a half a mile of Yosemite's Hetch Hetchy reservoir.
It supplies 85% of the water consumed by 2.6 million people in San Francisco and several communities in three adjacent counties about 200 miles (320 km) to the west.
With the flames so close, ash fell on the surface of the reservoir on Monday, but water samples from the supply were testing clean by the late afternoon, according to a San Francisco Public Utilities Commission spokeswoman.
"There continues to be no change or impact to water quality or delivery from the Hetch Hetchy Reservoir," the utilities commission said in a statement.
The Rim Fire, named after a Stanislaus National Forest lookout point called Rim of the World, has already damaged two of the three hydropower generating stations linked to the Hetch Hetchy reservoir that supply electricity for all of San Francisco's public facilities, such as hospitals and firehouses.
The city has drawn on reserve power stored for emergencies and purchasing additional electricity on the open market to make up for the difference.
The blaze has destroyed about two dozen structures and some 4,500 dwellings remained threatened, while air tankers including DC-10s have been deployed.
The USFS said in a statement: "Heavy reliance on aviation resources has been critical in an effort to slow the fires progress and allow suppression resources to establish indirect control lines in areas where accessibility and safety can be achieved.
"The availability of heavy aircraft is pertinent to the success of suppression efforts."
Nearly 4,000 people are involved in fighting the fire, which started during the afternoon on August 17.
Firefighters have also rushed to protect historic groves of giant sequoia trees, some of the tallest and oldest trees on Earth, from the blaze.
Workers have removed leaf litter from the ground and installed sprinklers to dampen any flames.
Most of the 1,200-square-mile Yosemite National Park has remained open to the public, although 13% of its 1,500 camp site have been closed.