Thursday, September 8, 2011

Incident Highlights Chemical Sabotage Risk

An article on the Portland (ME) Daily Sun website describes a chemical incident at a wastewater treatment plant that highlights a form of chemical sabotage not addressed by the Chemical Facility Anti-Terrorism Standards (CFATS) regulations. Of course, since this took place at a wastewater treatment plant, even if the risk were addressed by the CFATS rules, they would not have applied.

Incident Description

According to the article, someone pumped about 500 gallons of industrial grade bleach into a sodium bisulfite storage tank. A well understood chemical reaction proceeded to take place that produced heat and chlorine gas. The tank was apparently adequately vented because an explosion did not take place.

The article did not say if it was a facility employee or a delivery truck driver that was responsible for putting the wrong material into the tank. While accidents like this are not really common, they happen often enough that the prevention of these accidents is an almost mandatory topic in process safety reviews.

Incompatible Chemicals

Any facility that handles chemicals has to worry about the inadvertent mixing of incompatible chemicals. Almost all chemicals have at least one other chemical that, if mixed, will result in the production of toxic gasses, heat, fires, or some other dangerous byproduct. There are even well known materials that are incompatible with water.

For hazardous chemicals that require process safety reviews or hazardous operations reviews, one of the topics that should be addressed is how the combination of incompatible materials will be avoided. Typically the preventive techniques will involve a combination of engineering controls and administrative procedures. Unfortunately, process safety rules are not required take into account deliberate attempts to mix incompatible materials.

Sabotage Risk

One method of attacking a high-risk chemical facility would be to deliberately mix two chemicals that would produce a reaction that would result in a catastrophic release of toxic, flammable or explosive chemicals. This could be effected by an insider, a delivery driver (at facilities that allow drivers to unload chemicals) or through an attack on an industrial control system.

Currently the CFATS regulations only address the sabotage risk for a single class of chemicals that react with water to produce the potential for catastrophic releases or explosions. Part of the reason for that is that there is such a wide range of chemicals that could produce hazardous consequences if mixed with an incompatible chemical that almost all chemical facilities would be covered. For instance pool supply facilities store acids and concentrated hypochlorite that produce a similar reaction to that described in this incident. Grocery stores sell multiple products that produce similar reactions.

Counter-terrorism Response

Any facility that houses large quantities of chemicals with well-known incompatibility reactions should internally address measure to prevent their use in a potential terrorist attack. Simple measures include unloading procedures, different types of hose fittings on tanks storing incompatible chemicals, and ensuring that there are no common piping that could allow movement between incompatible tanks. These are common safety measures and should not cause an undue burden on most businesses.

High-risk chemical facilities need to specifically look at this issue, even with chemicals that are not listed on the DHS Chemicals of Interest (COI) list. Attacks on non-covered chemical storage tank that could affect covered storage tank would provide a method of attacking those tanks without introducing a complicated explosive device.

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