Evacuations were in effect for places including for the City of Mariposa, Mount Bullion Ridge Road from Highway 49, Old Toll Road between Corbett Creek Road and Highway 49 North, and

Mount Bullion Cutoff Road and Agua Fria Road from Highway 49 North to Highway 140. For more on evacuations sign up for Nixle alerts from the Mariposa County Sheriff's Office.

Road closures Tuesday included Highway 49 at Highway 132, also known as Coulterville Road, where access was restricted to locals with addresses in La Grange, Coulterville, and Greely Hill only. Also closed were Bear Valley Road at Exchequer Road, Hornitos Road and Old Toll Road, Highway 49 and Mount Bullion Cutoff, Highway 49 at Aqua Fria and Highway 140 at Aqua Fria.

Resources assigned to fire totaled 1,405 people, 217 fire engines, 35 fire crews, nine tanker planes, 11 helicopters, 35 bulldozers and 26 water trucks. The fire continued to threaten power lines south of the incident, lines that supply power to Yosemite National Park, Cal Fire commanders said.

Agencies on the fire included Cal Fire, Mariposa County Sheriff’s Office, state Office of Emergency Services, American Red Cross, Pacific Gas & Electric, the CHP, Mariposa County Public Works, Caltrans, the Bureau of Land Management, Mariposa County Fairgrounds, Mariposa County Fire and the California Department of Corrections and Rehabilitation.

When it was 95 degrees in Sonora on Tuesday afternoon, air temperatures were supposed to be about the same 40 miles to the southeast where the monstrous Detwiler Fire blew up to more than 25,000 acres, jumped Highway 49 and prompted evacuations in Mariposa.

Just a few miles south of the Tuolumne County line, residents, emergency responders, law enforcement, volunteers, inmate fire crews and professional firefighters were caught in a supercharged, wind-driven maelstrom of heat, smoke and flames: a firestorm.

Men and women who rushed to the Detwiler Fire on Sunday, Monday and Tuesday – whether they were law enforcement officers in shirt sleeves or wildland firefighters clad in helmets, goggles, head shrouds, turnouts, boots and gloves with 40 to 50 pounds of gear on their backs – these people were putting their lives on the line to help other people get to safety.

Winds 15 to 20 miles per hour were pushing the fire southeast toward Mariposa, home to about 2,100 people. Highway 49 was closed at multiple locations. Highway 140 was closed in the Mariposa area.

The chop-chop-chop of accelerating helicopter engines drowned out Fire Capt. Jerry Fernandez momentarily as he spoke by phone from Mariposa-Yosemite Airport on the outskirts of Mariposa.

“Helicopters, yeah, everywhere,” he said. Hundreds of structures, including mobile homes, ranch homes and historic buildings dating back more than a century, were under threat. By day's end, Cal Fire reported 1,500 structures threatened, eight destroyed and one damaged.

Extreme heat

Fernandez, who normally works out of Madera Station 7, was assigned to Cal Fire public information duties Tuesday. He remembers the 2015 Butte Fire that killed two residents and destroyed more than 500 homes in Calaveras County.

Asked to explain what it’s like for boots-on-the-ground firefighters, Fernandez said, “Wildland gear totals 25 to 30 pounds, with boots and packs up to 50 pounds, hose packs with two 100-foot lengths, brass couplings and other hardware, they can be 40 to 50 pounds, and add a shovel, McLeod or Pulaski tool, a Camelbak with up to a gallon of water . . . it’s 90 to 100 Fahrenheit out here, so yeah.”

Firefighters facing 50-foot flame lengths, on structure protection or setting intentional fires to consume fuel ahead of the blaze, can also face radiant heat levels 200 to 500 degrees hotter than normal air temperatures, Fernandez said.

Deputies and California Highway Patrol officers on the sharp end of evacuation efforts can often find themselves even more exposed to danger than firefighters on the front, Fernandez said. Law enforcement and other emergency responders in many cases are not wearing flame-resistant Nomex or Kevlar clothing to protect themselves from firestorm conditions when they go to help people.

“Smoke and ash, embers in the air, extreme temperatures, being close to the fire activity they are putting their lives at risk to warn people,” Fernandez said. “They’re checking on people and police are usually wearing their full patrol gear. That’s extra weight in challenging conditions.”

Mutual aid

As of Tuesday afternoon, personnel and equipment from Cal Fire’s Tuolumne Calaveras Unit assisting on the Detwiler Fire included three hand crews, four engine crews, crew and support for the spotter plane Air Attack 440, and two overhead personnel.

A contingent of 21 engine crews, four hand crews and three bulldozer drivers remained available for fires and other incidents in Tuolumne and Calaveras counties, Lindy Shoff with Cal Fire’s Tuolumne Calaveras Unit said.

Stanislaus National Forest fire managers did not have any personnel assigned to the Detwiler Fire as of Tuesday afternoon, said Diana Fredlund, a Forest Service public information officer.

Three engine crews, from Cleveland and Sierra national forests and Kings Canyon National Park, were helping cover the Stanislaus, and five more cover engines were expected to move into the forest by Wednesday.

Critical fire weather conditions with dry, gusty southwest winds and low humidity persisted Tuesday at the Detwiler Fire and in the Mother Lode. Forecasters with the National Weather Service and Cal Fire advised crew bosses there would be enhanced potential for fire starts and rapid spread, with locally gusty winds and low afternoon humidities.

Cal Fire described the fire as aggressive and extreme with uphill runs, active crowning and short-range spotting.

Early Tuesday, incident commanders on the Detwiler Fire told crews and their supervisors the blaze continued growing overnight due to ample fuel and steep terrain. Firefighters were advised to expect unfavorable weather conditions and aggressive fire behavior. The communities of Mariposa, Hunters Valley, Bear Valley and Hornitos were said to be under threat.

Back in Mariposa, Fernandez said, “Today our major issue is the high winds, 15 to 20, and extreme heat. It’s 110 degrees on the ground in places, there’s a lot of spotting issues, embers blowing ahead and igniting new fires. It’s a very dangerous situation for all personnel.”

Fuels feeding the Detwiler Fire on Tuesday included live oak trees, dead oak trees, mixed oak woodland, manzanita in places, cured, dead grasses, other ladder fuels and fire-dependent chaparral species, Fernandez said.

The mix of tinder-dry, flammable fuels and hot, dry, gusty winds combined to make an explosive cocktail of extreme fire behavior, with 50-foot flame lengths at times and swirling, flame-throwing devil winds in places.

“We’ve had years of drought,” Fernandez said. “We did get some rain of course. But everything is dried out now.”

Fear for animals

Bill and Nancy Main, who run the Mariposa Farmhouse Bed & Breakfast on Highway 49, stayed at their place to cut fire lines early Monday, said Nancy’s daughter, Roseann Scrivens of Los Angeles. They held out until Monday afternoon.

“When the wind came up and the fire jumped Highway 49 it quickly started getting too close for comfort and my family evacuated,” Scrivens said Tuesday after speaking to her mom. “This was approximately 4 p.m. as they were leaving. I finally spoke with them at around 7 p.m. for the first time since the last 12:30 a.m. text.”

Part of the Mains’ old farmhouse was built in 1894 and is a California Historical Landmark. They were more concerned about their animals and pets.

“They reached an animal rescue unit but the unit had not been able to help with the animals yet. Eight sheep, 90 chickens, two geese, one cat,” Scrivens wrote in an email.

By Tuesday afternoon, the Mains were staying south of Mariposa in Bootjack but they feared they may have to evacuate from there as well. Scrivens was nevertheless elated to learn at least some of the Bear Valley community appeared to be ok.

Her brother told her their neighbors had called the health food store in Mariposa to check in.

“The center area of town was successfully protected!” she wrote.

Under threat

The Detwiler Fire was reported just before 4 p.m. Sunday in the area of Detwiler Road and Hunters Valley Road, two miles east of Lake McClure.

As of 9 p.m. Tuesday the fire had scorched more than 30 square miles and it was burning out of control with containment estimated at 5 percent.

“This fire is moving so rapidly right now that right now we are focused on saving lives and property,” Amy Head with Cal Fire communications in Sacramento said just before 5 p.m. “When we have numbers, we will get them out to you.”

She said the agency did not have maps or an accounting of people people evacuated or animals.

“The wind on the fire is a west to northwest wind and the cause is under investigation,” she said.

Smoke concerns

Smoke and haze from the Detwiler Fire was plenty evident in Sonora and other Mother Lode foothill towns Monday. Winds scrubbed smoke away overnight and pushed it elsewhere, including places like Yosemite and the Desolation Wilderness near Lake Tahoe.

Smoke also drifted into the Tahoe Basin and down to Reno on Tuesday. By Tuesday night, a red-haze could be seen from Sonora.

In Yosemite, with Highway 140 closed in the Mariposa area, park public information staff tweeted that the only roads to get into Yosemite were Highway 120 from Tuolumne and Mono counties, and Highway 41 from Wawona.

El Portal Road remained open between Yosemite Valley and Parkline in El Portal, a park spokesperson said.

Air quality in Yosemite was being monitored. The park remained open, including campgrounds, hotels and restaurants.

Some employees with Aramark and Yosemite Hospitality, contractors for visitor services in Yosemite, live in Mariposa, said Lisa Cesaro, marketing manager for the concessioner. Aramark and Yosemite Hospitality were working to provide accommodations to those who may be impacted.

A spokesperson for PG&E said Tuesday about 100 utility personnel were assigned to fire response and safety on the Detwiler blaze.

Just after 4 p.m. Tuesday, Governor Jerry Brown issued an emergency proclamation for Mariposa County.

Contact Guy McCarthy at gmccarthy@uniondemocrat.com or (209) 588-4585. Follow him on Twitter @GuyMcCarthy.

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