Saturday, May 31, 2008

Ballistic Attacks on Hazmat Shipping

In yesterday’s blog (see: "Ballistic Protection for Railcars") I mentioned a news report about a 13-mile long chemical spill in Lyman, SC and used it to lead to a discussion about ballistic attacks on railcars. Today there is additional news about that spill which will lead into a discussion about ballistic attacks on hazmat shipments in general.

13-Mile Spill News

First the news; it should surprise no one that the chemical from that spill is still on the road; three days later. As you can imagine, cleaning up a liquid spill that is 13 miles long is quite an undertaking. An environmental firm has been hired to conduct ‘clean-up activities’ but rains are expected to wash the material off the roads and into drainage ditches. A heavy-enough or long-enough rain will make the problem ‘disappear’.

The solution containing metal wastes from an electroplating facility has dried leaving a film on the road. Authorities are cautioning people not to come in physical contact with the chemicals and to keep kids and animals away from the area. Such solutions are typically corrosive and can cause chemical burns. The EPA has set up a car wash to wash the chemicals off cars so that the waste water can be ‘properly’ disposed of.

The material has been identified as a hazardous waste from an unnamed electroplating facility. A couple has been charged with intentionally dumping this waste material on the road way. No details about their motive have yet been made public.

Ballistic Attacks on Hazmat Tank Trucks

If ballistic attacks are possible against TIH Rail Cars, they can certainly be made against tank trucks carrying hazardous materials. The tanks are of much lighter construction and are almost certainly susceptible to penetration by large caliber handgun rounds at typical pistol ranges. Most rifle cartridges provide enough power to allow through and through penetration at reasonable engagement ranges.

For pressurized cargos like the TIH chemicals discussed in yesterday’s blog the same issues discussed in that blog apply to an attack on a tank truck. There would be a relatively low volume stream of the chemical being sprayed out of the tank as the truck drove down the road. Casualties might be higher because of the closer proximity of people to such vehicles. On the other hand identification of the source of the contamination would be quicker and it would be easier to stop the tank truck.

Attacks on Non-Pressurized Hazmat Trucks

Most of the hazardous chemicals transported by trucks are not transported in pressurized containers. This makes the profile of an attack on this type of cargo completely different. The liquid will not spray out of the tank. Depending on the caliber of the weapon (the diameter of the hole) and the viscosity of the liquid there will be an initial stream of liquid coming out of the hole; much like you would see coming out of a garden hose.

As the level in the tank started to drop there would be a partial vacuum starting to form in the headspace of the tank. At some point that vacuum would be sufficient to prevent the flow of liquid out of the vehicle. A small amount of air would be sucked into the tank, allowing the flow to resume for a very short period of time. The vacuum would again build and the flow would stop. This would continue, allowing the tank to empty over an extended period of time. In short, you would have a ‘13-mile chemical spill’ all over again.

For most hazardous chemicals you would have a similar situation to the one seen in Lyman, SC. People would be cautioned to avoid the spill and a clean-up would be attempted. There would be some injuries, few if any deaths, and probably very little panic. The more likely emotional result would be anger at the attacker; counterproductive from a terrorist’s perspective.

There are some chemicals that react with water to for TIH chemicals. An attack of this type in a rainstorm would produce a trail of chemical reactions that would produce toxic chemicals. Fortunately, the volume produced would be quite small, producing much less of a risk for casualties than an attack on at TIH tank truck.

Optimizing an Attack on a Tank Truck

The problem of vacuum restricted flow is something that the chemical industry has had to deal with. The simple solution is to install a ‘vacuum breaker’ device. This introduces a controlled flow of a gas into the headspace that stops the vacuum from developing. The simplest such device is an open valve to the atmosphere.

Actually a simpler device would be a hole in the top of the tank about the same diameter as the hole being used to drain the tank. A through and through shot through the tank in a nearly vertical line would achieve this effect. A shot from ground level could achieve this, but would be rather obvious and the initial discharge would be very close to the shooter. A shot from above would achieve the same thing and protect the shooter.

The flow rate from such an attack would be faster and more constant. It would still not be sufficient to be a significant threat to the health and welfare of a significant portion of the ‘exposed’ population.


In short, while a ballistic attack would probably be one of the easiest attacks to complete against a chemical target, it is not an attack that would provide much in the way of casualties. An effective propaganda effort associated with the attack might be able to increase the ‘terror’ effect, but resentment rather than fear is more likely to be the result. That would be a counterproductive result from the view point of a terrorist.

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