On the 4th of May, 1988, a controller at the Pacific Engineering and Production Company
of Nevada (or PEPCON) chemical plant placed a call to local emergency services.
There had been an explosion, he informed them, and now everything was on fire.
This would have been a difficult situation for any business…
but was a particular cause for alarm with PEPCON; due to a series of unexpected events,
the plant was being used to store a massive excess of a dangerous chemical used in rocket
fuel.
In January of 1986, the Space Shuttle Challenger was launched as part of the ongoing US space
program.
Much to the shock and dismay of the country, and the world, it exploded shortly after take-off,
resulting in the death of all seven crewmembers on board.
In the wake of this disaster, further launches were suspended while the cause of the explosion
was investigated – something which meant some difficult decisions on the part of the
many suppliers involved in the space program.
PEPCON was just one of these – the plant had been responsible for manufacturing Ammonium
Perchlorate (or “AP”) a vital component of rocket fuel.
AP is an oxidiser – as well as being explosive when heated to very high temperatures, it
will massively promote the combustion of materials that it is combined with.
Now, with future launches called off, PEPCON was left with a huge excess of this product.
This excess was stored in thousands of plastic and metal drums on the premises of the PEPCON
chemical plant near Henderson, Nevada – just over 16 kilometres (or 10 miles) outside Las
Vegas.
The plant was often used to store some amount of product, but it had not been designed with
this amount of storage in mind.
There were, for example, no fire suppression systems in the areas where barrels of AP were
stored.
On the 4th of May, 1988, employees were at work repairing a building used to dry chemicals
as part of the manufacturing process.
The structure was made of steel and fibreglass, and had recently sustained some weather damage.
Workers were now using welding equipment to make repairs.
They were doing so at what was believed to be a safe distance from any barrels of AP,
and had also washed down the area to remove AP residue from surfaces before beginning
work.
At around 11:30am, in the vicinity of the welders, a small fire began.
It rapidly spread through the structure, resisting the attempts of workers to control it with
hoses.
As the fire took hold and it became apparent that the firefighting equipment to hand was
not sufficient to control it, plant employees began to evacuate.
Those who could used their personal vehicles, while others ran on foot alongside the road
to put as much distance as possible between themselves and the fire.
After around 20 minutes, a significant explosion took place.
This spread the fire still further, to the point that it engulfed the bulk of the AP
stored on site.
At this stage another explosion was inevitable… and when it came it was massive.
It was later estimated to be the largest non-military, non-nuclear explosion to take place in the
US in recorded history.
It had a yield comparable with that of a 1 kiloton nuclear bomb, or 0.25 kilotons of
TNT.
Emergency services had already been alerted by a call from an executive at the plant.
At the same time as this call was received, the chief of the Clark County Fire Department
happened to notice a plume of smoke on the horizon.
Correctly gauging that it arose from the PEPCON plant, he immediately directed all units to
the facility, then got into his own car and began driving there to direct operations.
Before he could reach the plant, however, the first explosion smashed in the windshield
of his car, injuring him and a passenger, and almost causing him to crash.
A fleeing employee stopped to warn the fire chief that there was likely to be another
more powerful explosion, and the chief accordingly retreated and pulled his firefighters back
to a safe distance before the second, larger explosion took place.
By remaining at a safe distance and not attempting to fight the fire until the explosive material
had been consumed, injuries among firefighters were kept to a minimum.
There were numerous smaller explosions, and a plume of flame continued to burn for several
hours even once the vast majority of the explosive material on site had been consumed.
This was eventually traced to a ruptured natural gas pipe which ran under the facility.
When this was closed off, the fire was finally brought under control, and firefighters were
able to approach the blast site.
The plant itself had been completely destroyed, and the explosions had caused significant
destruction within a 16 kilometre (or 10 mile) radius.
Residents within this area had seen windows shatter, power lines fall, and doors blown
off their hinges.
Around 400 people were taken to hospital to be treated for minor injuries, including a
large number of lacerations caused by broken glass.
It was also concluded that the explosion and fire might have released some irritant airborne
products.
Though these were not toxic, they did increase the overall number of hospital admissions,
with a large number of people suffering from respiratory irritation – some from communities
as far as 50 kilometres (or 31 miles away).
As a precaution, many nearby communities were advised to evacuate, although this resulted
in traffic jams that took so long to clear that the evacuation order had been reversed
by the time many residents were able to get away.
Closer to the plant the destruction was more comprehensive, with cars destroyed and buildings
flattened.
Two industrial facilities (a gravel works, and a factory that manufactured marshmallows)
had been all but completely incinerated.
At an airport near Las Vegas a Boeing 737 that was coming in to land had been shaken
by the shock wave, but had still managed to land safely.
Tragically, two PEPCON employees lost their lives in the explosion.
One was 56-year-old Bruce Halker, the plant manager.
Bruce was a wheelchair user, and there had not been sufficient arrangements in place
for him to evacuate as quickly as other employees.
The other casualty was 62-year-old Roy Westerfield, a controller at the plant.
Roy had survived polio as a child, and the infection had left him with some permanent
limits to his mobility.
Perhaps aware that he might not be able to escape as quickly as other employees, he voluntarily
stayed behind in order to inform the local fire department.
In each case, while the majority of employees were able to escape in time, there had been
no effective evacuation plan in place for their colleagues with limited mobility.
Several organisations investigated the cause of the fire, with reports issued by the United
States Fire Administration and the United States Department of Labor.
The former of these concluded that the fire was started inadvertently by the workers using
welding equipment, while the latter asserted that a natural gas leak from the pipe that
ran below the plant was the more likely cause.
PEPCON itself initially blamed the owners of the natural gas pipeline which ran below
the plant for the explosion, claiming that the fire must have originated there.
While it could not be definitively determined if this was correct or not, PEPCON was found
to be liable for the damages caused by the explosion.
After a long-running legal battle, they were forced to pay around $71 million in compensation
– a significant amount, given that their insurance policy only covered damages up to
$1 million.
The PEPCON disaster was one of several chemical-related accidents that lead to the passing of the
Chemical Catastrophe Prevention Act, later renamed the Chemical Accident Prevention Program.
This legislation holds facilities that manufacture and handle dangerous chemicals in Nevada to
high standards of accident prevention and emergency response.
Such legislation might have made a significant difference in the case of the PEPCON explosion.
It was found that the AP on site had been stored improperly in some cases, that staff
had not received adequate training, that combustible materials had been used in some buildings,
and that previous minor accidents had not been followed by any meaningful change to
working practises.
The plant near Henderson was not rebuilt.
Instead PEPCON changed their name to the Western Electrochemical Company, and moved operations
to a new facility near Cedar City in Utah.
Unlike the PEPCON plant, this facility was surrounded by an unpopulated no-build zone
that was larger even than that which was required by law, and was compliant with new regulations
implemented after the PEPCON explosion.
Despite this, the new plant did suffer a chemical explosion in 1997.
This accident caused one death and four injuries… but the total devastation of the PEPCON explosion
was, at least, avoided.