This last Wednesday there was a fatal accident at an ammonia storage facility in Swansea, SC. What marks this as being different from the large number of seemingly common reported anhydrous ammonia incidents, other than the death of course, is that this took place at a chemical facility rather than a food processing facility. Furthermore, the death took place off-site which may have an impact on the IST discussion taking place in Congress.
The release took place during transfer operations. The Tanner Industries facility was apparently receiving a truck load shipment of anhydrous ammonia (NH4). A transfer line ruptured while the material was being moved into a storage tank. Initial reports indicate that about 1,800 lbs of anhydrous ammonia was released from the hose before the truck driver was able to get the discharge valve closed on the truck.
As the liquid material exited the hose, the pressure reduction resulted in the conversion of the material from a liquid to a gaseous form. Additionally, some of the material would have reacted with moisture in the air to be chemically converted to aqueous ammonia (NH3OH), the form of ammonia typically found in very dilute form in household cleaners.
The gas cloud drifted off-site. Fortunately for the about 1,000 residents of the town of Swansea the wind was light and away from town. Unfortunately for the motorist that was killed, the cloud drifted across US 321. When her car stalled when it entered the cloud, the mother of two teenagers left the car in an attempt escape, but was quickly overcome by the toxic fumes.
An additional 14 people were treated for exposure to the fumes and seven of those were transported to a local hospital for additional treatment. Authorities credit actions of the truck driver with limiting the amount of the release and a state official who happened to be driving by with blocking the road and preventing other drivers from being overcome.
No Security Issues
There are no indications that this was anything other than an industrial accident. News reports do note that there was an electrified fence surrounding the facility, so Tanner Industries apparently take their security responsibilities seriously.
With a number of large anhydrous ammonia storage tanks on site, it is likely that this facility was a covered facility under CFATS regulations. With its isolation in a rural area, it is unlikely that that it was a Tier 1 facility. It will be interesting to see if Tanner Industries makes the same mistake that Bayer did earlier this year and try to use CVI markings on documents to limit the CSB discussion of their handling procedures.
The Chemical Safety Board has a team on-site and may end up adding this accident to their short list of formal investigations. Until their investigation is complete we really can’t make a definitive statement about the cause of the accident or what could have been done to prevent the accident. There are some indications of how Tanner dealt with safety issues.
First it is apparent that there were systems in place to prevent the storage tank from draining out through the ruptured hose. This is important. The large amount of anhydrous ammonia typically found in these tanks would have resulted in a much larger cloud and potentially more injuries and deaths.
If news reports are correct, and the truck driver had to manually shut the discharge valve on the truck, the facility did not have high-flow shut off systems in place for truck unloading operations. These systems sense the high-flow rates associated with this type of accident and automatically shut off valves on the truck side of the hose, limiting the amount of material that would be discharged from the truck. These systems have been recommended by the CSB in other TIH chemical incidents, but have not been required by OSHA.
At first glance, the Swansea, SC facility should be a poster child for proper use of IST considerations. The facility that handles large quantities of an inhalation hazard chemical is sited in an isolated area where a catastrophic accident could only affect a limited number of people. This is reflected by the fact that this facility was not listed on either list in the CAP Chemical Security 101 report.
So, how then does this incident have potential IST implications? First, IST proponents will be quick to point out that if an incident like this can happen at a facility whose sole function is the handling of anhydrous ammonia, then it can certainly happen at food processing facilities in urban areas. Tanner Industry employees will certainly be more experienced and better trained at the techniques for handling this dangerous material.
Finally, if down stream users of anhydrous ammonia were to find substitute materials then there would be a reduced need for handling anhydrous ammonia at facilities like this. Reduced handling would seem to reduce the likelihood of accidents like this.
Emergency Response Plan
The one thing that this incident points out is that if a facility only relies on preventive measures to protect against the consequences of a release (accidental or deliberate) they are going to get caught short sooner or later. Facilities with sufficient volumes of toxic release chemicals to have an off-site affect need to have emergency response plans that include emergency public notification of significant releases. Facilities with large quantities of toxic release COI also need to consider their moral responsibility for providing at least token mitigation measures.
Automated alarm systems are widely available to alert a control room or security center of significant leaks.
Facilities like this that are going to have an immediate impact near their fence line should have audio alarms that can be heard within a reasonable distance of the facility to alert their neighbors of an impending toxic cloud. More distant neighbors can be alerted by phone alerts. All of those neighbors need to be notified in advance of what to do in the event of an alert.
The question of what to do with a major roadway near the facility is more difficult because the measures need to be coordinated with state and/or local highway officials.
A stop light system like those used at many fire stations would probably be the easiest system to establish. The light remains green for normal conditions and only turns red in the event of a chemical emergency. This would probably need to be backed up by an automated sign that would provide emergency information. A backup response by local law enforcement personnel would also be recommended.
Finally, many inhalation hazard chemicals have some affinity for water or are chemically converted to less hazardous forms when they react with water. Facilities can mitigate the affect of releases of these chemicals by using automated fog machines and water sprays to reduce the size of, or even eliminate, the toxic cloud. Systems must include provisions for collecting runoff, but disposing of hazardous waste is better than dealing with off-site deaths and injuries.
I’ll be watching the follow-up on this tragic incident. The public response from Tanner Industries has been encouraging, but it will be interesting to see if they can sustain that response. Probably more important will be to see if the CSB conducts a full investigation of this incident and what the result of that inspection will be. Because of the wide spread use of anhydrous ammonia in commercial cooling systems, I hope that CSB takes advantage of this incident to look at anhydrous ammonia handling.
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