Phoenix, Arizona, February 28, 2007 - In a final report issued today, the U.S. Chemical Safety Board (CSB) concluded that insufficient safety margins, a lack of engineering safeguards, unclear procedures and training, and an absence of published guidance were among the causes of a release of up to 1,920 pounds of chlorine from the DPC Enterprises facility in Glendale, Arizona, on November 17, 2003.
The CSB report makes 14 recommendations to the company, local municipalities, and the Chlorine Institute.
CSB Board Member John Bresland said, "Our investigation revealed several factors that led to the release. Chlorine is a highly toxic substance that needs appropriate safeguards to prevent releases and protect the public, facility personnel, and emergency responders."
On the day of the accident, excess chlorine vented to a scrubber where it completely depleted the active scrubbing material (caustic soda), over-chlorinating the scrubber. The resulting decomposition reaction vented chlorine vapors to the atmosphere. Hazardous emissions continued for about six hours and led to the medical evaluation of five residents and 11 police officers, and the evacuation of 1.5 square miles of Glendale and Phoenix.
One of the root causes determined by the CSB is that DPC's single administrative safeguard, an operating procedure, did not adequately address the risk of over- chlorinating the scrubber. CSB Lead Investigator Jim Lay said, "It is necessary to integrate appropriate layers of protection into all processes handling hazardous chemicals. In this case, we recommended that DPC adopt safety features such as additional interlocks, automatic shutdowns, and mitigation measures to prevent the release of chlorine to the atmosphere due to over-chlorination."
The CSB previously investigated an August 2002 incident at the DPC Enterprises facility in Festus, Missouri, that led to the release of 48,000 pounds of chlorine, causing three workers and 63 residents to seek medical treatment.
The CSB report released today makes a total of 14 safety recommendations, including the following:
- Maricopa Department of Air Quality should revise DPC's permitted operating conditions to specify minimum scrubber caustic concentration;
- The Glendale Fire Department and Police Department should better integrate their incident command structure, improve communication, and hold joint hazmat training exercises;
- The Chlorine Institute, a technical research and safety institute for manufacturers and distributors of chlorine, should modify its "Chlorine Scrubbing Systems, Pamphlet 89" and other pertinent publications to address safety issues associated with over-chlorination;
- DPC should modify its corporate engineering standards to require layers of protection on chlorine scrubbers at DPC facilities.
The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as: equipment failures and inadequacies in safety management systems, regulations, and industry standards.
The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Visit our website, www.csb.gov.
For further information, contact Dana Arnold (602) 402-2200 cell (Phoenix) or Hillary Cohen (202) 446-8094 cell (Phoenix), or Daniel Horowitz, in Washington DC, at (202) 261-7613 or (202) 441-6074 (cell).