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Scott G Winterton, Deseret News
Crews burn a second batch of chemicals Monday, July 1, 2013.

SALT LAKE CITY — More barrels containing an unstable chemical were burned outside a Salt Lake warehouse early Tuesday.

The controlled burn marked the third in less than 24 hours. In total, officials had burned 280 barrels of the chemical Trigonox by Tuesday morning.

But Salt Lake City fire crews believed they were in the final stages of their operation at Quality Distribution Inc., 421 N. John Glenn Road (6070 West), that started with a small fire there nearly 48 hours ago. Officials said employees of the nearly a dozen businesses that had been evacuated since Sunday morning would be allowed to return to work Tuesday.

Just after 12:30 a.m. Tuesday, the Salt Lake City Police Department's Bomb Squad ignited 144 drums of Trigonox in a 120-foot-long, 2-foot-deep trench dug by Salt Lake City public utilities employees.

Trigonox is an organic peroxide that can become unstable at 68 degrees. When the temperature reaches 77 degrees, the process cannot be reversed and the chemical cannot be stabilized. Trigonox started a small fire inside Quality Distribution on Sunday when the building's air conditioning unit failed. That's when fire investigators discovered other barrels leaking.

Approximately 2,400 gallons of Trigonox were stored in the building in plastic 5-gallon drums. The explosive power of the chemical was reportedly the equivalent of a dry ice bomb, according to Salt Lake City fire spokesman Jasen Asay.

A quarter-mile radius around the building was evacuated.

Monday morning, about 40 drums of the chemical that were determined to be over 77 degrees and unstable were burned in a trench. The plan was to move the remaining barrels into refrigerated trailers outside the warehouse and ship them back to the manufacturer.

By Monday afternoon, however, the air conditioning in one of the trailers also failed. Rather than risk the safety of firefighters by having them go in and move the barrels again, the decision was made to burn the trailer with the 48 barrels inside. That happened about 8:15 p.m. Monday.

Each of the burns sent plumes of black smoke into the air.

"The fumes from the burned chemical cause very minor threats," Asay said. "All three of the controlled burns were conducted in an open field as representatives of the Salt Lake Valley Health Department and the Utah National Guard were on scene monitoring the situation for any environmental impact."

Seven additional pallets with 48 containers each did not have to be burned and were being stored in a refrigerated container at 20 degrees.

By Tuesday morning, a few firefighters remained at Quality Distribution to put out any hot spots that might spark up.

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Representatives from Quality Distribution were at the scene Sunday night and Monday morning but declined to speak to the media. The company's website says it has been in business in Utah for 18 years.

Asay said this was the first problem the department has ever with Quality Distribution. He also noted that the indoor sprinkler system was mainly responsible for extinguishing the initial fire Sunday morning.

Firefighters and hazmat crews from Salt Lake City, Murray, West Valley City, Unified Fire Authority, South Salt Lake, the Utah Highway Patrol and the Utah National Guard were all called to the scene to help resolve the situation.

Email: preavy@deseretnews.com

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