In Preliminary Findings, CSB Investigators Say DPC Enterprises Chlorine Leak on November 17, 2003, Resulted from Improper Safety Practices, Failure to Follow Written Procedures

June 9, 2004

At CSB Community Meeting, Board Members to Hear Testimony from Phoenix/Glendale Emergency Response Agencies, Company, and Residents

Glendale, Arizona, June 9, 2004 - In preliminary findings set to be delivered in a community meeting here tonight, investigators from the U.S. Chemical Safety and Hazard Investigation Board (CSB) say that last November's chlorine release at the DPC Enterprises Glendale facility resulted from the failure to shut off a chlorine transfer line when safety alarms sounded. The alarms indicated the near-depletion of an essential chemical in a safety device called a scrubber, but the CSB found it was common practice to allow chlorine to flow even after the alarms sounded, in violation of the company's own written procedures.

The chlorine release began while operators were transferring liquid chlorine from a railroad tank car to a tanker truck. As the tanker truck was filled with liquid chlorine, chlorine vapors were directed into the scrubber to prevent them from being vented into the atmosphere. The scrubber works by a chemical process where chlorine vapors are absorbed by a water solution with up to 20% caustic soda (sodium hydroxide), forming liquid bleach, a saleable byproduct.

CSB investigators said the company regularly ran the concentration of caustic soda in the scrubber down to less than 0.5% "a level that left a limited safety margin." The CSB found that on the day of the accident, November 17, 2003, the caustic concentration was allowed to drop to zero. The depleted solution could no longer absorb chlorine vapors, which then vented to the atmosphere. Furthermore, shutting off the transfer operation did not stop the release, as the over-chlorinated bleach solution broke down in a series of chemical reactions, generating chlorine gas.

Up to 3,500 pounds of chlorine were released in the incident. Authorities instructed more than 4,000 people to evacuate from the immediate area in Glendale and bordering Phoenix, using a reverse-911 call system. Fourteen people, including ten police officers, suffered chlorine inhalation symptoms and required evaluation at a hospital.

CSB Board Member John Bresland, who accompanied investigators to the accident site, said in prepared remarks for the meeting, "Companies which manage or produce chlorine have the responsibility of handling it safely. Chlorine gas is highly toxic by inhalation, and the CSB takes accidents that involve the release of chlorine very seriously. Fortunately in this case, no one was critically injured."

CSB lead investigator John Murphy said, "Our investigation, while preliminary, shows that DPC had written procedures requiring transfer operations to be shut down when alarms indicated that the scrubber solution was in danger of becoming too weak to absorb chlorine. With the transfer halted, the procedures directed operators to use a chemical test to determine the exact caustic concentration in the scrubber solution. However, we found that it was common practice for plant operators to continue transferring chlorine after the safety alarms sounded while they conducted their analyses. On the day of the accident the narrow margin of safety ran out."

Investigator Mike Morris said, "When operators went to the scrubber to sample the solution, they heard a rumbling sound. They activated the emergency shut off system, which worked as designed, halting the transfer operation and stopping the chlorine flow into the scrubber. By then a series of chemical reactions was underway and operators had no means to stop it. Chlorine continued to be released."

Investigators said the large multi-agency emergency response, with the Glendale Fire Department in command, was largely effective. More information is awaited from testimony to be heard at tonight's meeting. The meeting will be held at Glendale City Council Chambers at 5850 W. Glendale Avenue at 6 p.m. The public is invited to attend.

CSB Board Member John Bresland will preside at the meeting, accompanied by Board Member Rixio Medina. After CSB investigators report on the investigation, board members will hear testimony from panels of emergency responders and community representatives including: Glendale Assistant Fire Chief Tom Shannon; Glendale Assistant Police Chief Andrew Kirkland; Phoenix Police Commander Stephen Forster; Tim Newbill, executive director of the Maricopa County Local Emergency Planning Committee (LEPC); Rev. Ron Friesen, chairman of Black Canyon C.L.O.U.T.; Steve Brittle, LEPC member and president of Don't Waste Arizona; and Jamie Johnson, president of the Sevilla Neighborhood Association. A representative from DPC is expected to speak, followed by a public comment period.

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 failure as well as inadequacies in safety management systems.

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. Further information about the CSB is available from For more information, contact Sandy Gilmour Communications, 202-261-7614 / 202-251-5496 (cell). In Phoenix: Dana Weidaw, 602-402-2200 (cell).



Back to news