Board Member John Bresland, who accompanied the investigation team in Phoenix, said, said the preliminary investigation indicated a need to investigate further the immediate and root causes of the chlorine release. "Chlorine is a highly toxic chemical used in a wide range of chemical processes throughout the United States," said Bresland, "and we want to see what lessons can be learned from this accident to prevent releases in the future."
The release, which caused authorities to evacuate residents from the immediate area and close neighboring streets for hours, occurred as chlorine was being transferred from a railroad tank car to a tanker truck. Excess vapor in the process was being vented to a scrubber, an environmental control device designed to prevent chlorine from escaping into the air. The scrubber failed to function properly and allowed chlorine gas to escape.
Authorities said 14 people, including 10 Glendale police officers, were treated for chlorine-related symptoms, including nausea, throat irritation and headaches.
The CSB investigation team examined the offloading process at the chlorine repackaging plant, and interviewed workers, operators and plant managers. They have gathered information from local police and fire departments concerning community notification and emergency response.
The team requested documents relevant to DPC's process at Glendale, and will be consulting the Chlorine Institute (the industry's main trade association) and other companies that manufacture or process chlorine on safety practices in chlorine handling.
Testing will be performed on the emergency shutdown valves attached to the rail and tank trucks and on the equipment used in the scrubber system that is supposed to prevent overloading and warn operators of impending failure and the potential for a chlorine release.
Bresland said the team would return to Washington and begin piecing together information from the interviews, testing and other data.
This is not the first contact CSB has had with DPC Enterprises: the board completed an investigation in May of a massive chlorine leak at a DPC Enterprises facility south of St. Louis, which occurred Aug. 14, 2002.