Authorities said the plant handles both the fertilizers anhydrous ammonia and ammonium nitrate, the latter of which was used in the 1995 Oklahoma City bombing and several other attacks, such as the first bombing attempt at the World Trade Center in 1993.
Ammonium nitrate makes big explosions, be they accidental or intentional, said Neil Donahue, professor of chemistry at Carnegie Mellon University. It is stable, but if its components are heated up sufficiently, they break apart in a runaway explosive chemical reaction, he said.
“The hotter it is, the faster the reaction will happen,” he said. “That really happens almost instantaneously, and that’s what gives the tremendous force of the explosion.”
About a half-hour before the blast, the town’s volunteer firefighters had responded to a call at the plant, Swanton said. They immediately realized the potential for disaster because of the plant’s chemical stockpile and began evacuating the surrounding area.
The blast happened 20 minutes later.
The U.S. Chemical Safety Board was deploying a large investigation team to West. The ATF team that investigates all large fires and explosions was bringing fire investigators, certified explosives specialists, chemists, canines and forensic specialists. American Red Cross crews were helping evacuated residents.
Records reviewed by The Associated Press show the U.S. Pipeline and Hazardous Materials Safety Administration fined West Fertilizer $10,000 last summer for safety violations that included planning to transport anhydrous ammonia without a security plan. An inspector also found the plant’s ammonia tanks weren’t properly labeled.
The government accepted $5,250 after the company took what it described as corrective actions, the records show. It is not unusual for companies to negotiate lower fines with regulators.
In a risk-management plan filed with the Environmental Protection Agency about a year earlier, the company said it was not handling flammable materials and did not have sprinklers, water-deluge systems, blast walls, fire walls or other safety mechanisms in place at the plant.