Salt Lake City Fire Department spokesman Jasen Asay said hazmat officials did not think the burning was cause for environmental concern, but Salt Lake Valley Health Department representatives were on the scene to monitor potential problems.
Hazmat personnel searched Monday afternoon for any more compromised containers of Trigonox, a type of peroxide. They found an additional 720 gallons of the volatile chemical and decided to destroy it sometime after 11 p.m. to avoid igniting that much material in the direct sunlight, Asay said.
They dug a new trench twice the size of the original to detonate the larger amount.
Another 96 5-gallon containers of the chemical were potentially salvageable and were placed on a refrigerated trailer to be shipped back to manufacturer. However, the refrigerating equipment malfunctioned and began to blow hot air, rather than cold air, into the trailer, Asay said. About 8:15 p.m., firefighters discovered the extra heat had destabilized the chemicals to the point that firefighters could not remove the containers. With help from the Salt Lake City Police bomb squad, crews moved the trailer to the ditch in the field and burned it down, containers and all.
Problems with the chemical began about 9:30 a.m. Sunday with a fire of still undetermined cause at the company site. Once the blaze was doused, firefighters discovered the heat had caused bulging and in some cases leaking in many of the peroxide containers.
"When Triginox reaches the temperature of 68 degrees Fahrenheit, the chemical becomes unstable. Once the chemical's temperature passes 77 degrees Fahrenheit, the chemical cannot become stable again," Asay said.
At 95 degrees, the chemical begins to generate its own heat and can become explosive, in essence turning the containers into large pipe bombs. On Monday, when hazmat workers ignited the containers in the ditch, their temperatures reportedly had topped 90 degrees.
"[The chemical] is extremely sensitive to sunlight and ultra violet rays and can heat up rapidly. Especially with the high temperatures we have had during the daytime, we don't want these containers laying in an open trench with the sun beating down on them," Asay said.
A 2,000-foot radius area from the trench had been cleared and remained off-limits to non-emergency personnel Monday afternoon.
In addition to Salt Lake City, Unified Fire Authority and Murray hazmat crews, the Utah National Guard's 85th WMD CST unit and South Salt Lake hazmat personnel were on the scene Monday, Asay said.
Quality Distribution has specialized in the storage and distribution of hazardous materials since 1995 and maintained an "unblemished safety record," according to its website. It's the only place in Utah prepared to handle all types of hazardous materials, the website said.
Reporter Michael McFall and Erin Alberty contributed to this story.