Salt Lake City Fire Department spokesman Jasen Asay said the first load of the chemical Trigonox was burned at 8:10 a.m. Monday. The second, at 8:15 p.m. Monday, came after firefighters had moved 48 of the five-gallon containers of Trigonox into a refrigerated trailer. They later discovered the unit's cooling gear had malfunctioned.
The containers were too unstable to be removed from the trailer so the trailer was moved and burned.
"Once it was determined that the chemical had begun to decompose [it was decided to conduct] a controlled burn rather than risk the health of firefighters in an attempt to move the containers," Asay said.
The third burning of the chemical occurred at 12:31 a.m.
"[Those] containers were placed in a freshly dug trench [and burned by] the Salt Lake City Police Bomb Squad. Firefighters were close to the scene, ready to extinguish the fire," Asay said.
Salt Lake Valley Health Department and Utah National Guard experts monitored all the burns for potential environmental impact.
In all, 280 containers of the chemical were destroyed.
It was not anticipated that any more of the chemical stockpile roughly seven, 48-container-stocked pallets would need to be burned. Instead, they were put on refrigerated transport and returned to their manufacturers.
As for the fire at the warehouse, investigators believe malfunctioning air conditioning allowed the chemical containers to destabilize, bulge and leak. The leak is thought to have begun a small fire that was largely extinguished by an indoor sprinkler system.