Analysis: West Fertilizer report details sequence of a catastrophe

Print

How the West Fertilizer Co. fire began still isn’t known. But the probe has unveiled the detailed sequence of a catastrophe: Heat, pressure and shock made dual explosions, milliseconds apart, that killed 15 people and left a town to mourn, clean up and start over.

Something started a blaze in the seed room of the company’s fertilizer and seed building, a 13,000-square-foot structure by the spur rail on the northeast side of town.

It could have been an old golf cart stored there, or a problem with the warehouse’s electrical wiring, or arson. The evidence, investigators from the Texas State Fire Marshal’s Office and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives said Thursday, is insufficient to prove any of them.

Still, they reconstructed most of what happened and laid it out in public for the first time:

The seed room was on the building’s north end, blown to oblivion along with most of the rest of the company’s assets. The crater, 93 feet across and 10 feet deep, marks its location.

Parked inside the seed room was “a rickety old golf cart,” West Mayor Tommy Muska said, having seen workers driving it many times. It was battery-operated, recharged by plugging it into an outlet.

Nearby, in the same building, were wooden bins that held about 50 tons of ammonium-nitrate fertilizer, piles of a solid chemical formed into tiny spheres — think of the look of DippinDots ice cream. Outside, a rail car held an additional 100 tons of fertilizer.

For 22 minutes, the fire burned — through the time when volunteer firefighters got the call, responded, asked for backup and started preparing for what might come.

Here is what came: The fire kept getting hotter, raising the temperature of some of the ammonium nitrate — that is, shifting the chemical toward instability and increasing the likelihood that it would explode if something heavy struck it.

Something heavy did. It was debris and equipment from the fiercely burning and rapidly collapsing building, and it set off an explosion.

That first detonation set off another — thousandths of a second later, so fast that witnesses couldn’t tell them apart, but a frame-by-frame examination of their videos did.

So did the U.S. Geological Survey’s earthquake-detecting seismograph west of town at Lake Whitney — two distinct impacts.

All told, about 28 to 34 tons of ammonium nitrate exploded, but an additional 20 to 30 tons in the building did not. The fertilizer in the rail car did not explode either.

The amount that did detonate had the explosive power of 15,000 to 20,000 pounds of TNT. It flung bits of buildings and vehicles up to 2.5 miles, though most of the debris fell within 3,000 feet, more than a half-mile.

The search for answers on the ground took a month of combing through 14 to 15 acres, even sifting through hundreds of thousands of pounds of corn and milo by hand. It turned up an enormous amount of evidence but not enough to prove any specific cause to a scientific certainty.

That left three possibilities.

One was the battery-powered golf cart. All the investigators could find was a brake pad and an axle, so they couldn’t prove that the cart had an electrical problem that started the fire. Neither could they prove it didn’t have one, so it stays in the mix.

Over the past 15 years, tens of thousands of golf carts have been recalled because of fire risks, the Consumer Product Safety Commission says. Most were gasoline-powered and had problems with fuel leaks from various causes.

One was a battery-powered Club Car model recalled in February 1999 because of electrical problems that posed a fire risk. The make and model of the cart at West Fertilizer wasn’t clear Thursday.

Another possibility was an electrical system fire. Investigators exonerated the heavy-duty, 480-volt system in the warehouse that ran the big equipment. But the separate conventional 120-volt system couldn’t be ruled out, so it stays in.

The third was arson. On that one, investigators refused to comment except to say that only the part of the investigation on the ground was closed.

Staff writer Scott Goldstein contributed to this report


Story By: Randy Lee Loftis

Original Link: http://www.dallasnews.com/news/west-explosion/headlines/20130516-analysis-west-fertilizer-report-details-sequence-of-a-catastrophe.ece