​​​About 9:30 a.m. central daylight time on September 13, 2002, a 24,000-gallon-capacity railroad tank car, DBCX 9804, containing about 52,450 pounds (6,500 gallons) of hazardous waste, catastrophically ruptured at the BASF Corporation (BASF) chemical facility in Freeport, Texas. The tank car had been undergoing steam-heating to permit the transfer of the waste to a highway cargo tank for subsequent disposal. The waste was a combination of cyclohexanone oxime, water, and cyclohexanone. The railroad tank car, the highway cargo tank, and the transfer station were destroyed. (See figure 1 for a postaccident photo of the transfer area.) Two nearby storage tanks containing oleum (fuming sulfuric acid and sulfur trioxide) were damaged and released about 10,650 pounds (660 gallons) of material. Twenty-eight people received minor injuries, and residents living within 1 mile of the accident site had to shelter in place for 5 1/2 hours.

​​The National Transportation Safety Board determines that the probable cause of the rupture of railroad tank car DBCX 9804 was overpressurization resulting from a runaway exothermic decomposition reaction initiated by excessive heating of a hazardous waste material. Contributing to the accident was the BASF Corporation’s failure to monitor the temperature and pressure inside the tank car during the heating of the hazardous waste.

​We made recommendations to the Research and Special Programs Administration​, the Occupational Safety and Health Administration, and the Environmental Protection Agency​.