Friday, August 22, 2008

Anhydrous Ammonia Mass Casualty Event

There is an interesting set of articles on about a 2004 incident at a South Dakota meat packing plant where an anhydrous ammonia leak injured 100 personnel on site. The articles focus on the management of the incident as a mass casualty incident, so there is little information provided about the actual cause of the incident. Even so, there are some interesting observations that should be of interest to anyone developing an emergency response plan for a high-risk chemical facility.


Evacuation Plan


One of the first problems the responders encountered was accounting for personnel. With an outside temperature of 10°F people evacuating the contaminated area of the facility quickly looked for a place to get warm. Some went to the administration building, others got in their cars and left the facility.


All facilities have evacuation plans. They usually concentrate on getting people out of buildings. Once the people are outside most plans designate a primary assembly area. Chemical facilities concerned about fumes affecting the assembly area will probably include a secondary assembly area for poor wind conditions.


This incident points out that environmental conditions other than just wind need to be taken into account when planning evacuation routes and assembly areas. Facilities in areas that routinely experience sub-freezing temperatures need to take this into account. It may be something as easy as portable heaters or as complex as inflatable shelters.


Secondary Attacks on Assembly Areas

High-risk chemical facilities have additional considerations that need to be included in their evacuation planning. A common terrorist tactic is to execute a two-phase attack. Once the initial attack is executed and the response occurs the secondary attack is initiated to engage responders. A perfect target for this type of secondary attack would be the assembled workforce for the chemical facility.


 An attack on the assembled plant personnel would have the obvious affect of increasing the casualty count. It would also remove a source of trained personnel that could be expected to help in the response to the attack. And, as in any secondary attack, it ties up additional emergency response personnel that should be dealing with the effects of the primary attack.


The attacks can be executed in a variety of ways. A suicide bomber could be infiltrated into the facility as a driver or vender. A car bomb could be parked outside of the fence line near the assembly area. An armed team could be positioned in an area where they could take the assembly area under small arms fire.


Terrorist Identification of Assembly Areas


Identification of assembly areas would be part of the typical pre-attack surveillance plan used by professional attackers. Long term observation of the facility could show the surveillance team where the assembly area is by watching employee behavior during periodic facility drills. The same result could be obtained by observing facility response to minor attacks or bomb threats. Finally, insider information, deliberate or inadvertent could provide the attackers with the same information.


Protecting Assembly Areas


The emergency response plans for high-risk chemical facilities already looks to protect facility personnel by having them move to a safe area in the event of a facility emergency. Safety is currently defined as free of chemical contamination. That definition needs to be revised for facilities facing the risk of a potential terrorist attack.


One simple technique to reduce the chances of the assembly area becoming a secondary target is to deny the adversary the ability to identify the target. Selecting an assembly area that it is out of public view would be a first step to denying that information to a surveillance team. Facility personnel need to understand that the location of the assembly areas is part of the facility security information that should not be disclosed to outsiders.


Physical protection of the assembly area is more difficult. Constructing bomb-proof bunkers is not practical. Isolation of the area from public access and observation does provide a certain amount of physical protection. Berms or blast walls can be constructed to help protect against car bombs. The standard bomb detection procedures used to protect the facility against explosives being smuggled into the facility will prevent suicide bombers from attacking the assembly area.


Finally, the security response portion of the emergency response plan needs to include the requirement for security personnel to proceed to the assembly area to provide local protection for the employees, contractors, and site visitors seeking shelter in that area. These security personnel should be trained to lookout for the signs of a secondary attack on those people.


Prior Planning Essential


In an era where there is a significant possibility that high-risk chemical facilities may be the target for a terrorist attack it is important that a great deal of thought and planning should go into the facility site security plan. Part of the planning should be directed at the selection and preparation of the assembly area where facility personnel will seek safe haven in the event of an emergency. Proper prior planning will help prevent that site from becoming a secondary terrorist target.

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