Chlorine Incident Kills Two

This weekend there was an unusual incident in Mississippi where an auto accident involved a rural water treatment works. It resulted in the breach of a chlorine gas cylinder and the death of the two occupants of the car. As is usual, the details about the accident are sketchy, but with the help of Google Maps® and some industry knowledge, we can ferret out some lessons.

The Facility

The news article reports that two people were in a stolen car driving down a rural road when the “car slammed into the utility station, rupturing a large tank of chlorine”. In rural America, the only kind of ‘utility station’ that houses chlorine gas is a local drinking water pumping station. Searching Google Maps we can find that utility station here, on the west side of the road.

Looking at it on Street View®, we see a large, white, horizontal tank within a chain-link fenced enclosure. There is a small box-like structure, a pipe, a well-pump and an electric service pole with a nearby electrical panel.

I suspect that the reporter thought that the large white tank was a chlorine tank, but that is certainly not the case. First off, that tank is way too large; it would contain multiple years’ worth of chlorine gas for a facility this size. Second, chlorine gas is delivered in portable cylinders. For a facility of this size, that is typically a 50-pound cylinder that looks somewhat like a welding-gas cylinder. Two such cylinders will be found in the white box to the right of the tank; the one in current use and the backup for when the first is emptied. By the way, that large tank is a water tank, providing the pumping station with surge capacity.

The Accident

Looking at the map, I would guess that the car was proceeding north on Palmer Creek Drive, probably at a high-rate of speed. Instead of making the curve to the right, it continued straight and hit the large water tank. As part of the collision either the chlorine control box, or more likely the chlorine gas line from the box to the water system was damaged, releasing a small yellowish green cloud of chlorine into the atmosphere. It is not clear (and will not be until the autopsies are complete) if the chlorine gas, the injuries from the collision of a combination of the two caused the deaths of the occupants of the car.

There were chlorine gas related injuries to ‘several responding deputies and at least one fire fighter’. The Street View data is from 2013 and I cannot see any chlorine gas warning signs. It is quite possible that deputies responding to the accident did not know about the chlorine gas at the facility and approached the scene too closely. Fortunately, the small cloud would have dispersed enough to leave it a less-than-deadly concentration that they walked into, so the injuries were reportedly fairly minor.

Local residents were instructed to shelter-in-place in an abundance of caution. Again, with the small amount chlorine gas present, there was almost certainly no more danger at nearby residences than would be found in sniffing at the top of an open household bleach container.

Commentary

Since the incident happened on Saturday night it was almost certainly a joy-riding accident. If it had happened twelve hours later, there would have been a very remote chance of it being an attack. There is a church located next to the treatment works it would have been remotely possible that the incident was an inept attempt to gas the congregation.

It would have been fairly easy to accomplish that type of attack by entering the facility with a pair of bolt cutters and a pipe wrench. But, again, releasing the chlorine gas at the facility would have resulted in a less than deadly gas cloud at the church, even if the breeze was blowing in the correct direction.

Of course, an even more effective attack could have been executed by removing the gas cylinders from the facility and then piping the connection into any sort of facility air-handling equipment that the attackers desired. Depending on the size of the facility, a lethal concentration of chlorine gas could possibly be introduced fast enough to cause some deaths. A large number of serious injuries and panic could certainly be an expected result.

There are no requirements under either the EPA water facility security regulations or the DHS Chemical Facility Anti-Terrorism Standards for physical security of the chlorine tanks at facilities of this sort; the facilities are just too small to make regulations cost effective. As is fairly typical, the padlocked gate on the chain-link fence and a padlock on the chlorine control box are the only security measures in place. Even if video surveillance or intrusion detection devices were in place, the response time to such rural locations is long enough to allow perpetrators to successfully leave the facility.

Chemical Alarms

There was an interesting article on the Apalachtimes.com this week about a leak of a chlorine cylinder at a water treatment plant. A leaking 150-lb chlorine cylinder was detected by a local chemical alarm. The local area was evacuated, the cylinder was isolated and removed, and the area remediated. No injuries were sustained and the water treatment facility continued to operate as normal during the incident.

Gas Alarm

So, what made the incident interesting? What first caught my eye was the following:

“According to Manuel Aguilar, who oversees the water treatment plant, he arrived for work at about 6:30 a.m. and soon found the plant’s alarm, which detects the presence of chlorine in the air, was going off.”

Any facility that manufactures, stores or uses toxic inhalation hazard (TIH) chemicals typically uses chemical alarms to notify personnel in and around the area of the release of the TIH chemicals. By definition, TIH chemicals like chlorine can cause serious injury or death at relatively low concentrations. Even when chemicals like chlorine have distinctive odors the human nose cannot distinguish between relatively safe or unsafe levels of the chemical in the atmosphere.

Ideally chemical alarms used in TIH containing facilities should perform two functions. First they should act as a warning to those in the local area that are not wearing the personal protective equipment (PPE) necessary to operate in an exposure situation to evacuate the area as quickly as possible. Second it should serve as notification to initiate emergency response activities. In facilities that are not manned 24-7, there should be an off-site notification system to a response agency that is operational 24-7.

The Response

According to the news report Aguilar checked the chlorine tank in active use to see if it or any of its connections were leaking; no leak was found in the active system. Then:

“When he walked to where the chlorine gas canisters were secured, he could smell the pungent odor of chlorine, and noticed one of the 150pound canisters had ice builtup [sic] around an apparent leak at its base.”

Now there are a couple of things wrong with this picture. First off, since the active cylinder and the stored cylinder were stored in separate locations, the gas alarm should have indicated which location had the gas leak. It appears that there were sensors in the two locations, but the alarm indicator did not apparently indicate in which of the two areas that a leak was occurring. This would make it more difficult for emergency responders to locate the leak.

The second problem is that there is no way that Aguilar should have been able to smell the chlorine leak since he should have been in proper PPE when investigating a leak of unknown size and origin. And that PPE should have included a respirator. The fact that he looked for a potentially leaking tank without PPE probably indicates that either he was inadequately trained about the hazards of chlorine gas or that small leaks were relatively common and he had stopped taking the training that he had received seriously. The former is quite common.

Fortunately for the unprotected Aguilar the leak in the tank had essentially been stopped by the formation of chlorine gas hydrates. The evaporation of the chlorine liquid leaking from the bottom of the tank (nice picture here) created ice from the water vapor in the air which encapsulated much of the chlorine gas and ended up at some point blocking further leakage. If the full 75-lb (estimated) of chlorine lost from the cylinder had been in vapor form the concentration in the air could have been enough to cause serious injury or perhaps death to Aguilar when he entered the area.

The Ideal

Here is probably what should have happened. Sometime in the middle of the night (when the leak started) the person on duty at the Public Works Department should have received an alarm notification from the water treatment plant. The alarm would have indicated the location of the alarm (the cylinder storage area) and the chlorine concentration in that area. Calls would have been made to the local police and fire department and the facility manager. Based upon the location of the alarm and the chlorine gas concentration the facility emergency response plan may have called for local evacuations or shelter in place for the houses and business adjacent to the facility.

Depending in the training available (this is a small facility and full hazwoper training is typically not provided to facility personnel in such facilities) a team from the facility, local fire department and/or regional HAZMAT team would have suited up and entered the facility to investigate the leak.

Chemical Security

There is nothing in the article about security at the site, and that is to be expected since this was a leak incident not a security incident. Having said that, you can look at the facility on Google Street View and see that the cylinders not in use are being stored outside (which, to be fair, reduced the risk to Aguilar in this situation) with the only security being a chain link fence with two locked gates very close to the cylinders. The only thing securing the cylinders to the facility are the cloth safety straps designed to keep them from falling over.

If this were a facility covered by the Chemical Facility Anti-Terrorism Standards (CFATS) program those security measures would be totally inadequate. Unfortunately, Congress in its infinite wisdom exempted water treatment facilities from CFATS coverage because the EPA had its own water security program in place. This facility apparently meets those (obviously very lax) standards.

The CFATS program treats 150-lb chlorine cylinders as a theft-diversion risk. The idea is that the cylinders like these could be used by terrorists to attack indoor gatherings of people (like shopping malls, churches or schools). Or they could be used in conjunction with an explosive device to make an improvised chemical bomb (like we have seen used in Syria and Iraq by ISIS). In any case, preventing the theft of this type of cylinder takes a lot more than just a chain link fence with gates that can be opened with a pair of bolt cutters.

KUDOS: I would like to mention that the news report from David Alderstein was very professionally done. I was particularly pleased to see the description of the chlorine hydrate that was provided; a very nice touch. It is not often that we see chemical incident news reports handled this well in the press.

Chlorine Theft Scenarios

One of the things that a professional blogger does is to keep track of how people get to his site; it helps us work at keeping them coming. One of the tools that I use to do this is Google Analytics®, an on-line tool that lets me keep track of referring sites and search engines that people use to find my site. One of the things that it tells me is the key words people use in search engines that brings them to my writing. A key word phrase that has been creeping up the charts over the last couple of weeks has been “Chlorine Theft Scenarios”. That’s more than a little odd, since I can’t find any where that I have actually written on that specific topic, though I have looked at chlorine threat in passing on a number of occasions. So, I’ll correct that oversight now. Theft and Release COI Chlorine is one of the DHS Chemicals of Interest (COI) that falls under two separate categories; it is both a theft/diversion COI and a release COI. That means that facilities with large quantities of chlorine gas would be concerned about the consequences of an on-site release that would affect large civilian populations. Facilities with smaller quantities of chlorine gas do not present much of an off-site hazard as the dispersion of the chemical would reduce the potential health risk. Instead, DHS would be more concerned about a terrorist stealing the more portable containers of chlorine gas and then using them to release the gas at some other location where the dispersion area would be compact enough to keep the gas at a toxic concentration. The screening threshold quantity (STQ) for chlorine as a release-toxic COI is 2,500 lbs. There have been some complaints for the 2,500 lb STQ because this would theoretically allow a facility to have one-ton cylinder on site and remain below the threshold. In practice most facilities would at some point have a second cylinder of chlorine to switch over to once the first was emptied. Trying not to get the replacement cylinder on site until the primary cylinder contains less than 500 lbs would be a good theoretical procedure, but one that would periodically fail in actual practice. The STQ for chlorine as a theft-toxic COI is 500 lbs. This is a bit more problematic. The next smaller size standard shipping container for chlorine gas is the 150-lb cylinder. Even smaller lab-scale cylinders are available. A facility that utilizes the 150-lb cylinders could have three full cylinders on site and not be required to file a Top Screen; thus they would not fall under CFATS under the current rules. DHS recognized that the wide spread use of these cylinders in industrial water treatment and a number of chemical manufacturing processes would make it impractical to regulate at the less than 150-lb level. In the preamble to the final rule on Appendix A, 6 CFR part 27 (72 FR 65407) DHS noted that: “DHS believes that quantities less than 500 pounds would capture facilities that are unlikely to present significant consequences.” They further noted that: “Overall, DHS’s approach toward chlorine recognizes that chlorine is distinct from other WME precursors in terms of its broad utility and availability.” Stealing Chlorine Gas Now, a 150-lb cylinder is not a man-portable container in the classic meaning of the term, but it could be routinely handled with a pallet jack (think manually powered fork-lift). One would not expect these to be easy to steal. I have, however, reported on the theft of one of these cylinders in Houston, TX in 2007 and two similar thefts in California earlier that year. There is no telling how many other thefts may have happened, but never made it into the press. Chlorine Cylinders as Weapons The Chlorine Institute Pamphlet 74 provides estimates of the areas that would be affected by the release of chlorine gas from various storage/shipping containers. It estimates that a 150-lb cylinder would have a gas cloud at 20 ppm concentration (really dangerous but not probably not deadly) that would extend about 0.6 miles ( about 3200 feet) from the source of the leak with a cloud width of up to 0.2 miles (about 1000 feet). That dispersion is based on an open air release with a steady state wind speed. In an enclosed space like a mall the danger area would be smaller, but the concentration could be high enough to reach deadly levels in many areas of the building. Re-marked as a helium cylinder the material could be placed at a party goods store or balloon kiosk in the mall. The first time that it was used to fill a balloon the person operating the system would probably be overcome before they could shut the valve. The cylinder would be emptied before emergency response crews could respond with properly equipped personnel.

Alternatively, an electronic valve could be placed on the cylinder and it could be opened by a cell phone call or computer command. Again, remarking the cylinder as a helium cylinder could allow it to be placed at any number of places without undue suspicion. The discharge of the chlorine gas on a busy shopping day could cause hundreds of deaths and serious injuries as well as wide spread panic.