FLAGSTAFF, Ariz. (AP) Three towering concrete stacks that were the most visual reminders of a coal-fired power plant that operated for decades along the Arizona-Utah state line came down on Dec. 18, 2020.

The 775-ft. (236-m) structures loomed over the Navajo Generating Station, a 2,250 megawatt plant that closed in 2019 as natural gas became a cheaper alternative for electricity. Their flashing lights became a beacon in the community and a sign to travelers in a remote area that they were approaching Page.

"I have mixed emotions because I've spent most of my life as a constructor, and now I'm wearing a different hat in the demolition mode," said Gary Barras, a project management director of the Salt River Project, the Arizona utility that operated the plant. "I know personally how hard it was to design and build those stacks."

A series of booms echoed through the region that includes iconic tourist destinations such as Lake Powell, slot canyons and Horseshoe Bend as the stacks fell one by one. Clouds of dust covered what's left of the power plant, sitting low on the landscape before drifting away.

Thousands of people lined roadways and gathered in parking lots to watch it happen.

Environmentalists and some members of the Navajo and Hopi tribes fought years to shut down the plant that was among the largest in the West in favor of a switch to renewable energy.

"We are witnessing an artifact of a time when a coal-fired power plant was preferable to damming the Grand Canyon," said Roger Clark of the Grand Canyon Trust. "We've since learned that cooking the planet to keep Phoenicians cool is a bad idea."

The power plant was built to power the Southwest and a canal system that delivers Colorado River water to Arizona's major metropolitan areas. It shut down in November 2019.

The stacks came down in a way that's similar to cutting down a tree. Crews sawed the back side of the stacks so they would fall to the northeast largely on to concrete pads where water treatment, ash handling and brine concentrator systems once stood.

Crews also gutted transformers, wiring and elevators from the first 30 ft. (9 m) of the stacks to prepare. Small blocks of concrete were cut and knocked out of the structures to weaken them. Windows and vents were removed and reinforced to keep the stacks from twisting, said Nathan Betts, construction manager for Tetra Tech, the company overseeing contractors on site.

To prevent the stacks from falling earlier, crews didn't release the last bit of tension until the morning of. Dec. 18 before detonating about 1,530 lbs. of dynamite.

The stacks fell sequentially within seconds of one another. Crews will come in after the dust settles to separate rebar from concrete and recycle what they can.

No one was allowed within a 2,000-ft. (609-m) radius of the stacks for safety reasons. The original stacks were the same size but had been reduced to 220 ft. (67 m). They came down earlier this year.

The work is part of a $150 million decommissioning of the plant that is on land leased by the Navajo Nation. The buildings that housed the boilers — what Barras called the proverbial tea kettles — will go next, he said.

Environmentalists said they'll keep close watch to ensure the plant is cleaned up as required before the land is turned over to the Navajo Nation.

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