Fire retardant poses risk

A single-engine air tanker drops fire retardant south of De Beque in a 2005 wildfire. The scene was repeated recently at the Pine Ridge Fire.

A pilot flies through smoke to put down a line of fire retardant while fighting the recent wildfire that burned near De Beque. The Bureau of Land Management says 147,745 gallons of retardant were dropped.

By the time fire crews had fully contained the Pine Ridge Fire on July 4, nearly 150,000 gallons of fire retardant had been dropped on the 14,000-acre fire outside De Beque. A couple days later, surprisingly generous rains arrived.

Those July 7 rains, however, brought with them the possibility of retardant and ash being washed into the Colorado River, where, if the quantities were large enough, the runoff could pose serious risks to aquatic life.

But wildlife officials say a worst-case scenario appears to have been avoided.

The storm kind of caught us unawares,” said Dale Ryden, a fish biologist with the U.S. Fish and Wildlife Service’s Grand Junction office, who said they had just begun a couple days before to form a plan to deal with runoff from rainstorms.

“A little” ash and retardant was washed into the river, but agency crews have been on the river all week and have not yet found any fish kills, he said.

“It certainly doesn’t look like there’s significant impacts,” he said, though he thought those rains had only fallen on part of the burned area.

The Bureau of Land Management says that 147,745 gallons of fire retardant were dropped on the Pine Ridge Fire, which mainly burned on BLM land, over the course of 74 drops. The solution consists primarily of ammonium phosphate, which is also commonly used in fertilizers.

Though rare, the retardant can occasionally affect aquatic populations, maybe most spectacularly when a plane accidentally dropped about 2,000 gallons on the Fall River in central Oregon, killing all the fish over a stretch of about five miles.

But BLM spokesman Christopher Joyner said that adding huge quantities of anything to a river will have disastrous impacts. He also noted that the retardant does not pose a human health risk.

Still, he said, “as a policy we do everything we can do to avoid dropping on water.” Those policies also prohibit dropping retardant within 300 feet of a river or stream unless human lives are at risk.

In the case of the Pine Ridge Fire, he said, fire crews were presented with a special challenge as the blaze came all the way up to the banks of the Colorado River.

“It was a constant challenge for the crews, and they did a great job,” he said.

Thomas Fresques, a fisheries biologist with the BLM’s Silt office, is in town to help with monitoring any post-fire impacts. He said the closest to the river that fire retardant was dropped during the fire was about a quarter-mile.

He echoed Ryden’s assessment that the potential impacts from retardant do not appear to be a major concern right now and that he is not aware of any fish kills resulting from runoff yet.

Fresques also noted that the rain might have diluted the retardant a bit, so that not as much remains for future storms to wash into the river.

Both biologists were equally concerned about ash, which can clog gills and alter the pH of the river water, as retardant.

It does appear, however, that the exceptionally low river flows during this drought year may mean retardant and other runoff could have a greater potential impact on aquatic life than it might in wetter years.

“It certainly heightens concerns from retardant impacts, as there would be less water to dilute it,” Fresques said.

“You don’t have that dilution factor as much as you’d like, but that will hopefully be changing soon” due to recent rains in parts of the Colorado basin.

“It’s always a concern at low flows,” said Ryden, before pointing to an old pollution management dictum: “The solution to pollution is dilution.”


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