Thursday, July 7, 2011

Follow-up on CSB DuPont Report

When I wrote my blog post earlier today on the CSB notice in the Federal Register the referenced draft investigation report had not yet been posted on the CSB web site. When I rechecked this evening that report was available as is a copy of comments members of the Board and their investigators made today at a press conference in Charleston, WV.

I haven’t had a chance to review the lengthy draft report, but it appears to be a typical example of the thorough type of investigation documentation that we have come to expect from the CSB. The shorter news conference comments document is full of important information that all chemical safety and security professionals ought to review.

Safety as Security

All three of the safety incidents covered in this investigation involved dangerous chemicals that are listed in Appendix A to the CFATS regulations. Both oleum (fuming sulfuric acid) and phosgene are listed as release – toxic chemicals of interest (COI), while methyl chloride (also toxic, but significantly less so) is listed as a release – flammable COI. As is common with most dangerous chemicals, many of the safety procedures and equipment mentioned in this report should be considered dual use systems since they also play an important part in providing security for these chemicals against a terrorist attack.

Chemical Detection Alarms

The initial incident at the Belle, WV plant involved a slow but prolonged release of methyl chloride through a damaged rupture disk that allowed the chemical to be released to the atmosphere. Methyl chloride detectors were deployed in the area around where the chemical was used and the detectors did properly detect the release and appropriately alarmed. Unfortunately, because the system had an extensive history of false positive alarms, the operations personnel at the DuPont plant ignored the repeated alarms for a number of days.

If this release had been a deliberate act instead of an accident, an effective attacker would have provided for an ignition source to turn the flammable cloud into a fuel-air explosive that could have caused considerable destruction at the facility; destruction that would include release of other chemicals on site.

Properly deployed and maintained chemical detectors provide a two fold purpose in both safety and security planning. First they provide an early warning about the existence of a small leak to allow for an emergency response to prevent a catastrophic situation from developing. Second they provide a means to monitor the size, location and concentration of a chemical cloud to provide emergency responders with the appropriate information needed for an effective response.

False positive alarms are a common problem in any emergency notification system. Safety and security managers need to be cognizant of the fact that any alarm system that has excessive false positive notifications will soon be ignored by both response and operations personnel. All alarm notifications must be investigated and documented. The root cause for false positives needs to be determined and corrected if the alarm system is to have any value to a safety or security program.

Secondary Containment

The use of secondary containment is a common chemical safety technique used to prevent the spread of a chemical release from its storage container (the primary containment). The most readily recognizable form of secondary containment at most chemical production facilities is the presence of a dike wall around storage tanks that would retain the contents of any tanks that fail.

The CSB noted that the phosgene tanks at the DuPont facility were not protected by a secondary containment structure. Now, secondary containment for a chemical like phosgene is complicated. A simple dike will not suffice as the liquid phosgene produces a large toxic cloud that goes right over a dike wall. In the news conference notes the CSB investigators described what a secondary containment structure might look like:

“For example, phosgene cylinders should have been kept in an enclosure equipped with a ventilation system and a scrubber. If the enclosure were designed for human entry, workers should have been required to wear fully encapsulated protective equipment.” (page 8)
These secondary containment structures can be an integral part of a facility security program as well. It acts as another layer in security protection of the facility, making it more difficult for an attacker to get at the target. Additionally, it acts as a mitigating factor in any deliberate release, making it more difficult for the toxic cloud to reach the real terrorist target, the neighborhood around the facility.

There is no theoretical limit to the size of a secondary containment structure like this. For example, every nuclear reactor in the United States is enclosed in a similar containment structure designed to contain release of radioactive materials. Some of those structures would be large enough to handle even the largest chemical storage tanks.

Security Lessons Learned

Again, security and safety at high-risk chemical facilities are closely intertwined. It goes without saying that safety managers need to look at the lessons learned from the Chemical Safety Board investigations. The smart security manager will also take a close look at these reports to find ways to better protect their facilities from terrorist attacks.

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