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Exercise on recent accidents - Case 2: DPC Enterprises, L.P., Missouri

Background:
Around 9:20 am on Wednesday, August 14, 2002, a 1-inch chlorine transfer hose (CTH) used in a railroad tank car unloading operation at the DPC Enterprises, L.P., facility, near Festus, Missouri, catastrophically ruptured (Figures 1 and 2). The facility is located in an unincorporated area of Jefferson County. The hose rupture initiated a sequence of events that led to the release of 48,000 pounds of chlorine. The release continued unabated for nearly 3 hours.

Chlorine is a toxic chemical. When inhaled in high concentrations, chlorine gas causes suffocation. constriction of the chest, tightness in the throat, and edema of the lungs. At around 1,000 parts per million (ppm), 1 it is likely to be fatal after a few deep breaths. Chlorine gas concentrations of 10 ppm are classified as "immediately dangerous to life or health" (IDLH). Depending on a number of factors such as release volume, terrain, temperature, humidity, atmospheric stability, and wind direction and soda chlorine gas plume car travel several miles in a short time at concentrations well above IDLH. The majority of residents of the mobile home park were at work on the morning of August 14. Nevertheless, 63 people from the surrounding community sought medical evaluation at the local hospital; three persons were admitted and released the following day. Three workers also received minor skin exposure to chlorine during cleanup activities after the release.

 

The accident was investigated this incident for the following reasons:

  • The large quantity of release and prolonged duration, with potential catastrophic off-site consequences to the public.
  • The wide use of chlorine and the potential for similar incidents at other facilities.
 

Root Causes:

  1. The DPC quality assurance (QA) management system did not have adequate provisions to ensure that chlorine transfer hoses (CTH) met required specifications prior to installation and use.
  2. Branham Corporation, the CTH fabricator/distributor, did not have a QA management system to ensure that fabricated hose actually complied with customer specifications or that its own certification of materials specifications were correct.
  3. The DPC testing and inspection program did not include procedures to ensure that the process emergency shutdown (ESD) system would operate as designed.

Contributing Causes:

  1. The hose identification system of CTH manufacturers is inadequate to provide continuous positive identification of similar-looking structural braiding materials of construction, such as Hastelloy C and stainless steel.
  2. The DPC mechanical integrity (MI) program failed to detect corrosion in the chlorine transfer and pad air systems before it caused operational and safety problems. Wet chlorine caused excessive corrosion of the chlorine unloading piping and pad air piping systems, which prevented the ESD valves from closing properly. Potential sources of water

include:
Atmospheric moisture from inadequate capping of hoses and tank car piping assemblies.
Moisture from the pad air supply system.

  1. The community notification system was inefficient, which resulted in additional exposure to neighboring residents and businesses.
  2. DPC emergency preparedness planning was deficient. Lack of clear guidelines and mechanisms for community notification (e.g., community sirens, alert network); inadequate designation of responsibilities of facility emergency response personnel; lack of clear guidelines to determine if an incident requires facility response or off-site community response; inadequate training and drills; inaccessible location of emergency response equipment; and lack of clear guidelines for post-incident remediation resulted in DPC's inadequate preparedness for a large uncontrolled release.
  3. Jefferson County community emergency preparedness planning was inadequate for an incident of this magnitude. Better planning that involved all local emergency response and planning authorities could have improved the overall response and mitigation time on August 14.

 

 
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