Fire bombers drop fertilizer, clay, rust

Fire retardant more than just water

Posted: Friday, July 06, 2001

Fire retardant dropped by fixed-wing water bombers is more than just water, and it's not used to put out fires.

"It really only gains you time," said Mindy Sherrieb, incident information officer for the interagency fire management team working the Mystery Hills fire. "Retardant does not stop a fire, it just gives you time to get people in."

Television images have shown large airplanes dropping what looks like red water on the Kenai Lake fire, but the contents are much more complex than that.

Besides water, the main ingredient is fertilizer, ammonium polyphosphate, followed by powdered clay and an iron oxide dye.

"The dye is so pilots can see where they've hit from the air," said Gary Lehnhausen, a fire information specialist at the Kenai Lake command post.

At times, though, the water bombers, usually DC-6 or KC-97 airplanes, drop only water.

"But sometimes it looks pink, which is residual from the retardant," Lehnhausen said.

Helicopters use large fabric buckets to dip water from nearby lakes or ponds to drop on the fire. At the Kenai Lake fire, they use Kenai Lake. Depending on the size of the copter, the buckets hold anywhere from 150, 300 or 1,100 gallons of water.

For firefighters on the ground, water and retardant drops can be dangerous. Vince Welbaum has been fighting wildland fires for 23 years and knows to stay clear of water drops.

"The minimum distance from a helicopter drop is 100 feet, from a plane, it's 200 feet," he said. "That's minimum."

With thousands of pounds of water falling from the sky, Welbaum said the impact would throw a firefighter to the ground, perhaps killing him.

He said water drops from airplanes should be made high enough to not break trees, which would add to the danger on the ground.

"The same goes for bucket drops, unless there's a hot spot you want to put water on," he said.

The idea, he said, is to have the water disperse enough to fall like rain.

While the drops alone generally will not put out a fire, the retardant greatly reduces a fire's intensity when it hits, and water takes a lot of heat out of the fire.

"When the fire hits that stuff, it knocks it way down, allowing hand crews in there," Lehnhausen said. "Without helicopter or air support, we can't get in on the fire."



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