Firefighters struggle to contain huge wildfire raging in Yosemite area

TUOLUMNE CITY, Calif. – A huge wildfire near Yosemite National Park in California continued to threaten San Francisco’s water supply Monday, while officials warned that the blaze was so hot that it could send sparks into new, untouched areas.

Officials reported some progress. Stanislaus National Forest spokesman Jerry Snyder said containment of the fire was at 15 per cent Monday morning, up from 7 per cent the previous night. He said crews were helped by cooler temperatures caused at least in part by the shadow cast by the large plume of smoke.

The fire continued to grow, however, and was 234 square miles (606 sq. kilometres) in size – covering more ground than the city of Chicago.

READ MORE: 9 incredible photos of the Yosemite wildfire 

The fire, burning near one of the country’s most popular national parks, edged within a mile (1.6 kilometre) of the source of San Francisco’s drinking water and to some of the giant sequoia trees that are among the largest and oldest living things on earth. They can resist fire but were being sprinkled for protection.

The fire is now one of the biggest in California history, helped by inaccessible terrain, strong winds and bone-dry conditions. Strong winds threatened to push the blaze closer to nearby communities. About 4,500 structures remained under threat. At least 23 structures have been destroyed, though officials have not determined whether they were homes or rural outbuildings.

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“This fire has continued to pose every challenge that there can be on a fire,” said Daniel Berlant, a spokesman with the California Department of Forestry and Fire Protection.

The threat to San Francisco’s utilities prompted Gov. Jerry Brown to declare a state of emergency for the city. Water authorities were scrambling to fill area reservoirs with water before ash from the wildfire taints supplies.

Ash was falling on the Hetch Hetchy Reservoir but so far hadn’t sunk far enough into the lake to reach intake pumps.

General Manager Harlan Kelly Jr. of the city’s Public Utilities Commission said the city has a six-month supply on hand. If ash eventually causes turbidity, the city will begin filtering supplies. He was unsure of the cost.