Remote Sierra blaze is 5 percent contained

Firefighters in the Stanislaus National Forest are using the Tuolumne River like a "giant fire engine," pumping water from it to slow the spread of a fire that has been burning on the river's north slope since Saturday, authorities said.

The North Mountain fire, which was caused by lightning and has consumed about 1,010 acres, was 5 percent contained Wednesday evening, said Pat Kaunert, spokesman for the Stanislaus National Forest.

Firefighters from federal, state, county and local agencies have had to hike two miles over rugged terrain to dig the first fire breaks.

"There's no access for engines and little access for dozers," Kaunert said. "These guys have got to haul this stuff in like mountain goats."

Firefighters carried in hoseline and lightweight water pumps in backpacks, setting up intricate hose systems that they rolled up the side of the canyon. They snaked their way around the perimeter of the blaze from the heel, which is where the fire started and the coolest part of it, Kaunert said.

"The idea is to finally work your way up to the very hot portion up at the top and cut off its head," he said.

The fire is burning north of Highway 120, six miles southwest of Hetch Hetchy Reservoir. The highway is open but the trail to Preston Falls is closed, according to the Forest Service. There were 263 firefighters on the scene Wednesday, and more were expected to arrive as they were released from fires around the state.

The area poses "extreme logistical challenges," Kaunert said: steep terrain, heavy forest fuels and tinder-dry conditions.

"All of this makes for a firefighter's nightmare," he said.

Thick smoke has hampered attempts to attack the fire from the air for the past three days, Kaunert said. A cool layer of air has held unburned gas and smoke close to the ground "like the lid of a pressure cooker," he said. This "lid," he added, is common on the west slope of the Sierra. It generally lifts in the afternoon, pushed by warm air from the valley below.

"At some point, the heat of the fire will finally punch through that cooler inversion layer and basically vent the fire," he said. "That creates a chimney effect. The surrounding air clears up, and there's not as much smoke, but it causes the fire to burn more intensely."

The weekend's weather forecast calls for possible thunderstorms, which could include dry lightning and more new fires, he said.

No one has been injured and no communities or structures have been threatened. Firefighters have kept flames away from the historic North Mountain lookout tower, which was built from steel in the 1930s as a Civilian Conservation Corps project.

"When you picture a ranger standing on a tower looking out with binoculars, that's what this is," Kaunert said. "The tower belongs in a movie. It's that classic."

Bee staff writer Emilie Raguso can be reached at eraguso@modbee.com or 578-2235.