Officials leading the fight against the Rim Fire, which has scorched an area twice as big as Las Vegas in the heart of the Stanislaus National Forest, showed increased optimism that they were gaining the upper hand on the blaze Wednesday.
The Rim Fire overnight had grown to 192,737 acres - 312 square miles of mostly brush, oak and pine - but was 30 percent contained.
Much of the increased acreage was in the north and northeast. Some of the increase was attributed to deliberate backburning by firefighters, designed to stop the fire's spread.
Most of the unconfined area is in the north and northeast in a sparsely vegetated granite landscape, so is unlikely to feed the fire's spread significantly. Firefighting strategists pushed the fire in that direction by aggressively creating containment lines in the west, to protect communities along North Tuolumne Road and Highway 108, and in the south and southeast, near Groveland and along a line stretching from Pilot Peak to the Yosemite National Park boundary in Mariposa County.
The fire containment efforts have been aided by favorable weather, including lower temperatures, higher humidity and lighter winds, said Dan Berlant, Cal Fire spokesman.
Berlant said the fire should be fully contained by Sept. 20.
A containment estimate date of Sept. 10 was pushed back this morning due to forecasted higher temperatures.
Even with full containment, the fire will continue burning perhaps for months, until significant rain and snowfall can douse the remaining hot spots.
Coals could smolder underground even into next year, posing a danger to people walking through the woods.
Also a threat are thousands of "hazard trees" that are unstable and could fall. Along the Highway 120 corridor alone, 7,000 such trees have been identified by Caltrans, said Forest Service spokesman Jerry Snyder.
As a precaution and to avoid further erosion and destruction it the area, the U.S. Forest Service has closed the Groveland Ranger District and most of the Mi-Wok Ranger District to the general public. It's closed until further notice.
The Rim Fire has burned for nearly two weeks.
More than 4,800 firefighters and support personnel - coming from as far away as Los Angeles, New Mexico and New Jersey - have been assigned to the blaze, in addition to more than a dozen helicopters and several airplanes.
It's burned 11 homes, three commercial properties and 97 "outbuildings" - which includes dozens of tent cabins destroyed at the City of Berkeley's family camp, Camp Tuolumne.
Firefighting units Wednesday had pretty much contained the Rim Fire at the southwest side. They began mop-up operations. Mopping up a wildfire involves extinguishing and removing all burning material near the fire lines.
Some additional backburning was planned today at the fire's west side, around Duckwall Mountain, and contingency lines were to be cleared west and north of the fire.
Forest Service spokesman Steve Stine, from South Carolina, said the fire is being directed northeast, where it is expected to lose momentum in the rocky, sparsely vegetated terrain.
More containment lines were being constructed Wednesday near Hetch Hetchy. The fire has surrounded the southern and western sides of the reservoir that supplies water to the city and county of San Francisco, and also the town of Groveland.
Firefighters are also battling the fire's eastward movement toward popular sequoia tree groves in Yosemite National Park. The National Park Service has placed sprinklers around the Tuolumne and Merced groves as a preventative measure.
Fire crews working on the southern edge of the blaze Wednesday were conducting "burn outs" - which are controlled burns adjacent to the containment lines, Stine said.
"Burn outs" reduce grasses, shrubs and trees that can help wildfires "jump" across lines into unburned areas.
The fire Wednesday was being more aggressively attacked on the western flank because of the communities it could threaten along the Highway 108 corridor, Stine said.
Bulldozers were being used to construct large "contingency" lines in the area to protect the township of Tuolumne City.
Williams said that lines are more often constructed by hand crews because of the environmental impacts caused by bulldozers.
"Bulldozers cut down trees and make huge swaths in the earth, but they also make very effective fuel breaks," he said. "Hand lines can also be constructed in more steep and rugged terrains that bulldozers can't reach. So it all comes down to what your objectives are, how hot the fire is and how fast it's moving.
Williams said it would be "almost impossible" to determine exactly how many miles of bulldozer and hand lines have been constructed to contain the Rim Fire.
Forest Ranger Maggie Dowd, of the Groveland Ranger District, said the service is now trying to assess damage to roads, and a team will later determine what needs to be done to rehabilitate the forest.
"That's the other reason we've closed the forest as much as we have around the fire perimeter - because we have to mitigate the hazards," she said. "And that's not only the trees, that's also the road conditions."
Another pressing matter will be evaluating the landscape to prepare for rain-related erosion as fall and winter approach.
"We really need to start looking at soil, watershed conditions and figuring out immediate needs to take care of it before the rain comes and we get flash flooding," Dowd said, "because the mop-up for this is going to take months."