There was an interesting news story out of Deer Creek, OK earlier this week about an anhydrous ammonia leak caused by straight-line winds from a severe weather systems that blew through the State. The story notes that: “Shortly after the storms passed an anhydrous ammonia leak was discovered at a storage tank facility on the south side of Deer Creek.
There is no word about what type of facility was involved, but since this is a rural area it was probably an agricultural supply store (fertilizer) or a food packaging plant (cooling). In any case, the leak caused evacuations that would inevitably hamper recovery efforts from other storm caused damage.
Even the most paranoid amongst us would not dream of blaming straight-line wind damage as the result of a terrorist attack, but incidents such as this do provide a real world opportunity to look a physical vulnerabilities for bulk storage systems for chemicals of interest (COI).
Facilities that are susceptible to damage from wind-blown debris (even winds of 80 mph) will certainly be vulnerable to blast effects from nearby IEDs or VBIEDs. As this story notes ancillary equipment to storage tanks (pipes, pumps and valves) need to be protected every bit as much as the storage tanks themselves.
Also remember that while local physical security measures may limit direct access to these structures (and no PSM is 100% effective), action at a distance by blast effects is also something that must be considered. Blast walls, blast curtains or even just facility layout to prevent line-of-site access to vulnerable structures may all be used to protect against blast effects.
Where there is bulk storage of volatile COI (toxic, flammable and/or explosive) there should be leak detection equipment surrounding the storage facility so that there can be the earliest possible response (on-site and off) to leaking materials. The sensitivity of the detectors will be driven by the concentration of concern for the chemical involved.
The sensor network should be dense enough that there is enough of an overlap in coverage that damage to a single sensor from flying debris will not allow a significant leak plume to go undetected.
Leak detection and associated alarm networks should be considered both security and safety critical equipment for bulk storage areas containing COI. As such they should be on an uninterruptable power supply with redundant communications. Off-site access to the alarm data should be considered as a way to assist first responders in their initial approach to the situation.
During periods of increased risk (including approaching severe weather or floods) additional operational controls can be put into place to increase the security/safety of bulk storage facilities. This can include closing of manual valves on transfer and loading lines to limit the amount of leakage in the event of damage to the system.
Inventory adjustments or relocations may be worth considering. Moving volatile COI into pressure vessels may reduce the susceptibility to damage. Dispersing COI into multiple tanks can reduce the release amount expected from damage of a single vessel. All of these pre-incident precautions need to be considered carefully in advance as part of both the safety and security plans for the facility.
Safety and Security Planning are Mutually Supporting
The actual risk of a terrorist attack on any particular chemical facility in the United States is quite low. Facilities in this country are much more likely to feel the effects of severe weather than the effects of a terrorist attack. Fortunately, many of the safety measures used to protect a facility from the effects of severe weather will also be an integral part of the facility security plan.