To supporters of Searsport LPG tank: Industrial catastrophe is great risk

Posted Nov. 22, 2012, at 2:23 p.m.

OK, I’m “from away.” I’m a native of New Hampshire, but attitudes over there aren’t all that different. I’m not here on some extended vacation in paradise. I’m here because it’s a nice place to live, and I enjoy the decent people who are living here for the same reason.

I happen to be on the side opposing a proposed $40 million liquid propane gas terminal and storage tank, but not because I’d be offended to have to look at another tank in the Mack Point Industrial Zone. It is zoned commercial, after all, and I’m perfectly OK with Searsport’s long history as a commercial port.

Industry has its place. I see no good reason why folks who object to having a new structure sited in an industrial development should want to deprive the local economy of opportunities for jobs and tax revenues on purely aesthetic grounds. To my mind, that’s going over the top.

I’m not even opposed to the tank because it might increase congestion and wear and tear on Routes 1 and 3, or because it might have a negative impact on the tourist trade, or even because it might reduce my property value or its resale potential. I’m not planning to go anywhere any time soon.

The real reason I am opposed to the tank is safety, pure and simple. If the folks at DCP Midstream wanted to build their big, new tank and store gasoline in it, I’d be fine with that. There’s a lot of gasoline stored at Mack Point already, and I don’t see that as an issue. Gasoline is a liquid, and it won’t even burn unless it’s vaporized and mixed with air, as it is in the injectors of my car.

If a gasoline tank springs a leak, it’s usually pretty obvious, and even if leaking gasoline catches fire, it can usually be easily extinguished by a small crew with fire-suppressant, or even water, before it gets out of hand. Furthermore, gasoline burns at only about 1,650 degrees, which is well below the 2,500-degree melting point of steel, and therefore wouldn’t pose any threat to the integrity of the tank from which it leaked.

Propane, on the other hand, is a whole different animal. Although it’s a liquid as long as it remains inside the refrigerated tank, as soon as it leaks out, it becomes a gas. Not only is it harder to see and smell a propane leak, but every ounce of gas that escapes through the leak mixes instantly with air to form an explosive mixture. An expanding cloud of that explosive gas spreads outward until it encounters any ignition source, of which there are plenty in the environment. It then explodes, all at once, at a temperature of close to 3,600 degrees, which is definitely hot enough to melt steel.

What that means is that once the leaked propane explodes, there’s no way to prevent the steel body of the tank from melting, rupturing and releasing its full contents to the atmosphere, thus generating a far greater explosion. Technically, the process is known as a BLEVE (rhymes with Chevy and stands for Boiling Liquid Expanding Vapor Explosion). With the tank’s entire 22.7 million gallon contents exploding, that would be bad enough, releasing about as much energy as 33 Hiroshima-sized atomic bombs, but it wouldn’t stop there. The super-hot BLEVE would also melt all the other tanks in the farm, releasing and vaporizing their 55 million additional gallons of fuels to create an 87 million gallon Super-BLEVE equivalent to some 150 Hiroshima bombs, or a small hydrogen bomb.

That is exactly what happened near Mexico City back in 1984, when the PEMEX LPG tank farm in San Juanico developed a leak in the long supply line leading to one of the tanks. The leak wasn’t detected until the explosive gas cloud spread to the flare pit, whereupon it ignited and exploded, blowing all the tanks in the farm. It was the worst industrial catastrophe in Mexico’s history, killing more than 500 people, injuring more than 5,000 and leveling the town.

How much LPG was involved in the San Juanico disaster? 11,000 cubic meters, or 2.9 million gallons. That’s a little less than 13 percent of the capacity of the Searsport LPG tank. Now if you add the 55 million gallons of other flammable fuels currently stored at Mack Point, what went bang at San Juanico was a little less than 4 percent of what could go bang at Searsport.

Any way you look at it, that’s a lot of bang.

How big? Think the world’s biggest industrial catastrophes. Think Chernobyl. Think Fukushima. Maybe worse.

Right here, in midcoast Maine. It would put us on the map — or take us off it, for good.

David Laing, of Stockton Springs, is a retired assistant professor of geology at the University of Maine at Presque Isle.

David Laing 567 3700

Stockton Springs

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