As fire crews tried to slow the Pole Creek and Bald Mountain fires, which grew by more than 17,000 acres Friday night into Saturday, a new fire ignited in Herriman, burning homes and forcing evacuations.

As of Saturday afternoon, the Pole Creek and Bald Mountain fires in Utah and Juab counties had grown to a combined 86,107 acres. They have displaced approximately 6,000 people living in the Woodland Hills, Elk Ridge and Covered Bridge communities, in addition to those living along U.S. 89 from Nebo Creek to Thistle Junction, according to a news release from the Utah County Sheriff’s Office.

Those living in the Diamond Fork Canyon and Sheep Creek area have been put on pre-evacuation notice, according to the release.

The fire also forced officials to close U.S. 6 through Spanish Fork Canyon on Saturday. U.S. 89 in that area remains closed from mile marker 312 at Thistle Junction to the Utah-Sanpete county line.

Gov. Gary Herbert has said the two wildfires have the potential to be the most destructive of Utah’s fire season because of the numerous homes in the fires' paths.

Hundreds of Type 1 firefighters flooded into the fire area Saturday hoping to suppress the blaze, but fire officials said at a community meeting Saturday evening that high winds hampered the crews’ efforts earlier in the afternoon and made it impossible to use any aircraft but helicopters.

Evans Kuo, with Great Basin Management Team 5, said during the meeting that firefighters haven’t been able to get close to the fire line on foot either because of high winds and rugged terrain.

About 600 firefighters are now assigned to the Pole Creek and Bald Mountain blazes, Kuo said, with about that same number en route.

During a question-and-answer segment at that same meeting, a man criticized fire officials, saying their tactic of managing and confining but also letting those fires burn was a “stupid decision, and now every one of us is paying for it.”

David Whittekiend, Uinta-Wasatch-Cache National Forest supervisor, defended fire officials’ choice, saying, “We didn’t just let [the Pole Creek] burn. The firefighters were in place” assessing and digging fire lines. Seventy were assigned to that fire when it ignited.

Whittekiend said the Bald Mountain Fire began as one tree and officials didn’t believe it would move “because it sat for days.”

Because of high winds, Whittekiend said the fires started moving faster than firefighters could keep up.

“Throughout the summer — and I know this doesn’t give anybody any comfort — but we have been successful doing the exact same things throughout the entire forest,” he said.

Meanwhile in Herriman, Unified Fire Authority firefighters were called out about 1:50 p.m. to fight a “fast-moving, wind-driven” grass fire in the Butterfield Canyon area. Residents living in the Hi Country Estates Phase 1 neighborhood were evacuated, but were allowed back into their homes after 6 p.m., once the fire was under control.

UFA spokesman Matthew McFarland said the fire was bolstered by 30 to 40 mph wind gusts to grow to 100 acres, destroying two homes and one outbuilding in the process.

A juvenile is in custody for allegedly starting the fire by lighting a smoke bomb. McFarland said the fact that a seemingly “inert" firework like a smoke bomb could spark such a fire speaks to just how dry the vegetation is in that area.

About 150 people had been assigned to fight that blaze, the spokesman said. One firefighter and four police officers were treated for smoke inhalation.

By 6:20 p.m., McFarland said the fire was almost entirely contained.

The Great Salt Lake State Park in Magna was also closed and evacuated Saturday because of an approaching fire, according to its website. The fire was first reported just before 3 p.m. at 11800 West and Interstate 80, according to a 911 dispatcher.

That fire closed Interstate 80 in both directions between state routes 36 and 202, according to the Utah Department of Transportation. By 10:15 p.m., the highway was opened in both directions.

The fires have degenerated air quality values in the state, with moderate amounts of particulate matter over a 24-hour period recorded in Salt Lake, Tooele and Washington counties, as well as Lindon in Utah County, on Saturday, according to the Utah Department of Environmental Quality. The brunt of the dirty air in the Wasatch Front cleared into the afternoon, though Washington, Weber and Iron counties all recorded moderate air pollution levels as of 4:45 p.m.

Tooele County recorded the worst air quality values at that time, with levels of particulate matter reaching 111.6 micrograms per cubic meter, well into the air quality index’s unhealthy range.

The Utah County Health Department has issued a wildfire smoke advisory for the county. According to state fire officials, much of the smoke from the Pole Creek and Bald Mountain fires has traveled northeast and settled in the Strawberry Reservoir area, Heber Valley and the Uinta Basin.

(Jeremy Harmon | The Salt Lake Tribune) Spencer Hall tries to fix a reel while fishing with his wife, Katie, and son Jonas at Strawberry Reservoir on Saturday, Sept. 15, 2018. Behind them the sky was filled with smoke from the Pole Creek Fire.

Air quality is predicted to be at its worst again Sunday morning before clearing in the late morning and afternoon, according to fire officials. Forecasters predict the wind will carry the smoke into southwest Wyoming.

Correction: 5:26 p.m., Sept. 15, 2018 • An earlier version of this story misstated which areas recorded moderate amounts of particulate matter over a 24-hour period.