A recent propane explosion and resulting fire in Tacoma, WA severely damaged a foundry. A propane delivery truck and one or more on site propane tanks caught fire or exploded. An electrical sub-station was damaged, shutting off power to 13,000 customers. Portions of the delivery truck were thrown onto a nearby highway and portions of the road were closed until state inspectors could inspect bridge supports for possible damage. All 32 employees on site were accounted for, but three people, including the delivery driver, were hospitalized.
While a complete investigation of the incident is on going, the initial indications were that the fire originated in the vicinity of the delivery truck. There are no indications in any of the news reports that this was anything other than a horrible accident. There is not a hint of any report of any deliberate acts being involved and nobody has even mentioned the words ‘terrorist attack’ in any news reports. Having said that; lets play the ‘What If’ game.
A foundry is about as far as one can get from most people’s idea of what constitutes a chemical facility. While this facility would come under that definition, if DHS would ever get their Appendix A, DHS Chemicals of Interest, to 6 CFR part 27 approved, due to the large amount of propane on site (potentially 59,000 gallons according to a Tacoma newspaper account), I would expect that the security around this facility was limited at best; probably a perimeter fence and gate guard at best.
If a terrorist group wanted to get a bomb near one or both of the two large, on-site propane tanks, the simplest way of doing so would be on or in a propane delivery truck. The driver might be involved, and thus become a suicide bomber, or he might not know about a device in or on his vehicle. The driver might be a suborned employee of the gas company or a driver substituted after the truck was hijacked enroute to the facility. The truck could even be a complete substitute painted to resemble a delivery truck from the gas company. Given these alternative methods of this type of attack, what security procedures could have been put into place to prevent a successful attack?
The first layer of defense, working from the tanks outwards would be to isolate the two tanks from each other. This would limit the results of the successful attack to the explosion of a single tank. Furthermore, blast walls near the tanks could limit the effectiveness of any attack by directing the force of any explosion away from high value targets, people or high value capital equipment. Additionally, the unloading location could be physically isolated from either tank, by either distance or location of blast walls, to reduce the potential effectiveness of a truck mounted bomb. Next, all other delivery vehicles would be kept away from either tank or the unloading station by a secondary fence and vehicle barriers. Finally, neither of the propane tanks nor the unloading area would be visible from any fence line on the property; at a minimum a chain link fence taller than the tank, equipped with privacy strips would be between the tank and any fence line.
A propane delivery vehicle entering the restricted area around the tanks or unloading station would have to undergo a physical inspection before entry is allowed. A slow walk around inspection with all equipment doors open with the driver away from the vehicle would normally suffice. During periods of high terrorist threat potential, a bomb sniffing dog could be added. This could be done while the driver was having his paperwork checked and verified in an office. The driver’s identity would be verified with the propane company during this paperwork check.
A delivery truck would not be allowed through the outer perimeter gate unless a delivery was scheduled for that day and time period. The guard would have a truck number and driver’s name provided at the beginning of the shift or physically delivered by someone from the facility office before the truck arrives at the gate. When the gas truck arrives at the front gate the driver would have to enter the guard shack to prove that he was not under duress. A quick walk around inspection would be done by the gate guard. If no delivery was scheduled the truck would not be allowed enter the front gate. If the driver’s or truck identification did not match the list, the truck would not be allowed enter the front gate.
While none of these measures would provide absolute protection against a terrorist attack, they would provide enough security to make most terrorists look elsewhere for an easier target. The tank barriers, separation and separate unloading facility would slow down the progress of a terrorist attack so that authorities could be notified and appropriate facility evacuations could be initiated. Finally the blast walls and separation between tanks and supply truck would mitigate the effects of a successful attack. How a foundry could be a terrorist target will be discussed in a future blog.
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