Accident 5

Storage and distribution facility

Sequence of events
On the evening of April 17, a fire of undetermined origin broke out at the West Fertilizer Company Storage and distribution facility in West, Texas (USA). The facility had already closed for the day and was unattended. Firefighters found the warehouse building in flames and were in the process of extending hoses to fight the fire, and were applying some water to the blaze. Although the firefighters were aware of the hazard from the tanks of anhydrous ammonia as a result of previous releases, they were not informed of the explosion hazard from the approxi mately 60 tonnes of fertilizer grade ammonium nitrate inside the warehouse. While firefighters were positioned nearby, the ammonium nitrate suddenly detonated. A shock wave, traveling faster than the speed of sound, crushed buildings, flattened walls, and shattered windows. Innumerable projectiles of steel, wood, and concrete – some weighing hundreds of pounds - were hurled into neighborhoods. Twelve firefighters and emergency responders were killed along with at least two members of the public. More than 200 were injured and more than 150 buildings were damaged or destroyed. If this incident had occurred earlier in the day, many more people might have been killed or injured.

Causes
Investigators have confirmed that ammonium nitrate was the material that exploded, but the cause of the initial fire is as yet unknown. Nonetheless, preliminary findings suggest that lack of adequate prevention and mitigation measures in the storage facility may have substantially elevated the risk of a catastrophic event. In particular, the presence of combustible materials and the lack of fire protection system.

Important findings
• The warehouse where the ammonium nitrate was stored was made of wood and the ammonium nitrate itself was separated into wooden bins. The building also stored significant amounts of combustible seeds that likely contributed to the intensity of the fire.
• Existing professional standards for preventing ammonium nitrate accidents were confusing and contradictory and not up to date with current practice in other countries, For instance, they did not prohibit ammonium nitrate storage in wooden buildings or wooden bins.
• There were no monitors, alarms or automated fire protection measures in place to aid in obstructing the catastrophic chain of events following the ignition of the ammonium nitrate. According to professional standards, automatic sprinkler systems were not mandated unless more than 2500 tonnes of AN is being stored. It was estimated that only 30 tonnes that would have been necessary to devastate much of the town of West.
• Firefighters were not made aware of the presence of an explosive hazard and as a result conducted their response effort at an unsafe distance from the source.
• The plant was last inspected by the safety authority in 1985. It was not a priority for inspections because it was not a manufacturer and had no prior record of a major accident. Ammonium nitrate was not in the scope of environmental regulations for preventing accidents with offsite consequences.
• No standards were in place that restricted certain types of development, such as schools, nursing homes, and hospitals, around ammonium nitrate storage facilities.


Figure 4: The scene following the accident (Source – U.S. Chemical Safety Board)

Lessons Learned
• The only scenario which was considered as dangerous in the storage facility was the accidental release of anhydrous ammonia. Conducting comprehensive hazard identification, analysis and risk assessment where hazardous substances are stored or handled is a basic requirement when operating dangerous establishments.
• Separation of combustible materials from organic substances is recommended to reduce potential conflagration and explosion once an ammonium nitrate fire has started.
• It should not be considered acceptable under any circumstance that a site storing ammonium nitrate in bulk quantities is allowed to operate without proper fire prevention, protection and mitigation measures.
• Development should be restricted around sites that handle or store ammonium nitrate or in the case of existing development in close proximity of the site, appropriate prevention and protection measures should be in place to reduce the risk as much as possible.
• Local authorities should be aware of the dangers associated with ammonium nitrate hazards and oversee the sites in their jurisdiction as appropriate to the level of risk. Even sites with relatively small quantities can be significant risks if they are in close proximity to human development (See Figure 1).
• Local responders should also be aware of all ammonium nitrate storage sites in the area and the maximum quantities that might be present, They should be trained on how to fight ammonium nitrate fires in accordance with the current best practice.
• The operator of the facility did not learn lessons from past accidents including the Texas City, Texas (USA) Disaster of 1947 or the more recent accident in Toulouse, France of 2001 and many others that have been published. (http://en.wikipedia.org/wiki/Ammonium_nitrate_ disasters) Operators of ammonium nitrate sites should actively review lessons learned from past accidents and regularly update their knowledge on safety and risk management requirements.

More information: http://www.csb.gov
See also: EMARS Accident # 263 and El Dorado Chemical Co. Athens,
Texas 29 May 2014 at http://thescoopblog.dallasnews.com/2014/05/fire-reported-at-fertilizer-plant-in-athens.html

Safety principles

• Elimination/minimisation of the presence of combustible materials and incompatible substances (such as explosives) in close proximity to the ammonium nitrate.
• Avoid co-storage of combustible materials in the same location
as much as possible.
• Avoid strict confinement of the storage area; proper ventilation
limits the progress of decomposition should it occur.
• Prevent moisture absorption to avoid caking.
• Be aware of and follow appropriate safety precautions associated with AN fertilizer storage, including packaging stacking,
temperature and other elements.
• Ammonium nitrate may elevate combustion risks.
Follow established norms for mitigating fires, such as having a sprinkler system in place to minimize the risk of spread of a fire.
• Control ignition sources (e.g. hot work, smoking, vehicles)
with control of the electrical system in the storage.
• Contaminants, such as organic materials (oils or waxes)
may increase the explosion hazard of ammonium nitrate.
Handle off-specification, downgraded or technical grade fertilizer contaminated with organic material safely and
segregate them from other products.
• Even for short periods of storage of fertilizers
a risk assessment is recommended.

Further information on safety procedures for handling
ammonium nitrate can be found at the following links:
• http://www.hse.gov.uk/explosives/ammonium/
• http://www.ineris.fr/centredoc/synthese65281.pdf
• http://www.nfpa.org
• https://www.safework.sa.gov.au/uploaded_files/SSAN_Storage.T60.pdf

Major accidents involving fertilizers

Safety challenges most commonly associated with ammonium nitrate fertilizer hazards

The unique safety challenges associated with ammonium nitrate coupled with poor safety management culture could largely be considered the most important contributing factors across the accidents studied. Specifically, some of the most common factors associated with elevated risk to the population and first responders included:

• Insufficient fire prevention, protection and control systems were in place.
• There was a lack of knowledge of the inherent hazards associated with the handling and storage of ammonium nitrate fertilizers, and in many cases, specifically the potential decomposition of such fertilizers was not considered.
• The operator did not adhere to basic safety requirements for handling ammonium nitrate and dangerous substances generally.
• Existing regulations did not adequately recognize the hazards of sites storing and handling bulk quantities of ammonium nitrate, As such, oversight was inadequate or entirely lacking.
• Likewise, the authorities often failed to recognise potentially vulnerable land-uses around ammonium nitrate installations, a risk that can be substantially elevated if adequate prevention and mitigation measures are not in place. Where such measures are not in place, even relatively low quantities of ammonium nitrate can cause accidents with serious off-site consequences.
• Operators seemed unaware of the many accidents involving ammonium nitrate that have occurred in their own countries as well as around the world, despite wide publication in open sources. Hence, they did not take advantage of the lessons learned.
• Establishing adequate safety procedures in particularly relating of training and awareness of hazards.

The case studies provided in this bulletin are just a small sample of the reports available in the eMARS database involving fertilizers. Nonetheless, cases have been selected on the basis that they are somewhat typical of accidents involving fertilizers.


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Please note: The selected cases also include a number of lessons learned, not all of which are described. The bulletin highlights those that it considers of most interest for this topic, with the limitation that full details of the accident are often not available and the lessons learned are based on what can be deduced from the description provided. The authors thank the country representatives who provided advice to improve the descriptions of the selected cases.

General characteristics of fertilizers