West Texas and Ammonium Nitrate: Part 5

I am glad I put the kibosh on the direction I was going with this topic.  Actually it was my wife who told me to back off on the indignation.  That was good advice because while I was changing direction I learned of the 20 minute time frame from initial call to explosion.  Maybe others were aware of how quickly it happened, but I was not.  That information, that time frame, changes the dynamics.

In the post I wrote but did not publish I said this: "If you have responsibility for the health and welfare of people you should understand your job well enough to make sound decisions so that you don't hurt or kill people you are supposed to protect."

That assumes that had they had the information on ammonium nitrate's potential to explode it would have changed things.  Had they had an emergency plan in place, drilled on the plan, looked at every thing there was on responding to a fire where ammonium nitrate is involved, the outcome would have been different.

Maybe...but now I am not so sure.

I used to do emergency response to hazardous chemical incidents.  I have done a lot and they are always different.  They involve a lot of assumptions but follow the same basic measures.  Protect public health and minimize environmental harm.  So when I read this:

Associated Press interviews with first-responders suggest that firefighters' foremost fear was a poisonous cloud of anhydrous ammonia.

I went back to my old days as a HazMat responder and looked at it objectively.  What would I have told them to do if I was the guy in charge?

And if I am objective and honest with myself, I would have had them focus on the anhydrous ammonia tanks while we evacuated the people in the isolation area:

2012 ERG

I would have recommended that those folks 1.3 miles surrounding the facility - not just downwind - be evacuated, and until that time we would have concentrated on keeping the anhydrous ammonia tanks from rupturing.  Then I would have recommended, once the evacuation was underway, that since it is a large fire involving ammonium nitrate that we follow the ERG 140 recommendation:

2012 ERG 140

The 1.3 mile evacuation for the anhydrous ammonia would also cover the ammonium nitrate explosion potential.  When public safety was completed then I would have recommended letting it burn.

2012 ERG 140

That's what I would have most likely recommended in an EPCRA LEPC planning meeting and that's what I would have recommended at the time of the response.  In hindsight that would have been the wrong decision, as the AP points out:

They didn't know, and probably could not imagine, that the plant would soon explode into a deadly fireball and lay waste to much of the community. Instead, they were more concerned with preventing toxic gas from leaking out of the facility and drifting into nearby homes.

That's the focus I would have taken even if I knew there was 200 tons of ammonium nitrate in the building that was now on fire.

Why?

Because ammonium nitrate does not normally explode within 20 minutes of catching on fire.  It has the potential to explode, but that requires a shock wave to initiate the decomposition.  Under almost all normal conditions, ammonium nitrate behaves as an oxidizer and in a fire, though the potential for explosion is there, the concern is the intensity of the fire and the release of ammonia gas in the decomposition.

Ammonia nitrate in a facility that makes fertilizer should not explode.  Should not because that's not what we normally see it do.  That's not what it did in 2009 in Bryan, Texas 100 miles South of West, Texas:

Texas farm country is dotted with fertilizer plants in towns served by volunteer firefighters. But a 2009 blaze at the El Dorado Chemical Co. in Bryan, Texas, unfolded much differently than the disaster in West. Bryan firefighters knew a welder had accidentally heated up an ammonium nitrate bin and that the chemical was smoldering. They evacuated the area and let the facility burn to the ground. Nothing exploded. (AP)

Even though, as the AP points out: "...the plant's vast stockpile of a common fertilizer, ammonium nitrate, which can also serve as a cheap alternative to dynamite."

Yes, ammonium nitrate can be used to blow things up.  Farmers use it to remove stumps and rocks.  And yes, in the "1995 Oklahoma City bombing, and authorities said the plant made materials similar to that used to fuel the bomb that tore apart that city's Murrah Federal Building." (1)

But ammonium nitrate is just an ingredient.  The fact that it can be used to make a bomb makes it no different than acetone used to make Triacetone Triperoxide (TATP) or glycerin to make nitroglycerin.

Ammonium nitrate is an oxidizer, not an explosive.  It has the potential to explode, just like a propane cylinder hooked up to your grill.

The "potential" to explode and "will" explode are two different things.  Now in hindsight we can look at ammonium nitrate differently.  But hindsight was not what these guys had in the 20 minutes it took from the initial call to the explosion.

The one common denominator that must be present is an initiating source.  Fire is not normally the thing that does it.  Timmothy McVey lit a fuse to a blasting cap that initiated the ammonium nitrate/fuel mixture in five 55 gallon drums in the back of a Ryder truck.  The Boston Marathon bombers used ordinary fireworks to provide the explosives but that required a blasting cap on a timer to initiate the blast.  Ammonium nitrate can explode in a fire, but it takes a shock wave faster than the speed of sound to do so.  What, in 20 minutes, produced that shock wave that caused the ammonium nitrate to explode?

My focus would have been on evacuation and immediate concern of the anhydrous ammonia tanks rupturing.

My focus now changes with this new information.  How likely is ammonium nitrate to explode when it is involved in a fire?  That's the question we need answered for West.  What initiated the ammonium nitrate?

From there we can come up with better plans on how to store the ammonium nitrate and respond to a fire should that possibility happen.


Next post: West Texas and Ammonium Nitrate: Part 6