Rupture of a Railroad Tank Car Containing
September 13, 2002
NTSB Number HZM-04/02
NTIS Number PB2004-917003
Executive Summary: About 9:30 a.m. central daylight time on September 13, 2002, a 24,000-gallon-capacity railroad tank car, DBCX 9804, containing about 6,500 gallons of hazardous waste, catastrophically ruptured at a transfer station at the BASF Corporation chemical facility in Freeport, Texas. The tank car had been steam-heated 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. As a result of the accident, 28 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 tank car, highway cargo tank, and transfer station were destroyed. The force of the explosion propelled a 300-pound tank car dome housing about 1/3 mile away from the tank car. Two storage tanks near the transfer station were damaged; they released about 660 gallons of the hazardous material oleum (fuming sulfuric acid and sulfur trioxide).
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 Corporations failure to monitor the temperature and pressure inside the tank car during the heating of the hazardous waste.
The Safety Board identified the following safety issue during this investigation:
As a result of its investigation, the Safety Board makes safety recommendations
to the Research and Special Programs Administration, the Occupational Safety
and Health Administration, and the Environmental Protection Agency.