Tree-spraying chemicals detected in water

Without careful disposal, insecticide use could threaten water quality

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BY HARRIET HAMILTON
summit daily news
Summit County, CO Colorado
March 24, 2008

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SILVERTHORNE — The chemicals local towns and neighborhoods are spraying to prevent the spread of the pine beetle could be contaminating local water supplies, according to the Silverthorne/Dillon Joint Sewer Authority.

Last May, employees at the Silverthorne treatment plant performed a toxicology test on water that had been treated and was on its way out into the Blue River. The routine test — usually done twice a year — involved placing 20 minnows and 20 water fleas in a container of plant effluent and seeing how they did. After 48 hours, the minnows survived, but all 20 of the water fleas died.

“We’d been doing these tests for 10 to 12 years,” plant manager Mike Bittner said. “And we’d never failed one.”

The initial toxicology test didn’t identify any specific chemical, but it triggered increased monitoring and a series of more extensive investigation of the plant’s effluent. It wasn’t until July that test results returned to normal, and it took that long to pinpoint the chemical culprit: carbaryl — an insecticide also known as Sevin.

One of the three most commonly used pesticides in the U.S., carbaryl has been an agent of choice for the majority of those spraying Summit County’s lodgepoles to protect them from the pine beetles during the local beetle spraying season, which runs from May through July. As with other hazardous materials, it’s illegal to dump the insecticide into the sewer system.

At its peak, the concentration of carbaryl in the Silverthorne plant effluent was fairly small — only 3 parts per billion (ppb) — not enough, once diluted in the river, to have an impact on wildlife, but the fact that it showed up at all concerns Bittner. Stone flies, a common indicator of mountain stream water quality, are even more sensitive to carbaryl than the water fleas used in the toxicology test.

“It’s a food chain thing,” Bittner said. “You kill the stone flies— and that’s what the trout eats.”

So far, among Summit County water treatment plants, Silverthorne’s is the only one to find carbaryl in its effluence. The follow-up testing required because of the initial positive finding cost the Joint Sewer Authority around $15,000, Bittner estimated.

The results didn’t surprise High Country Conservation director Carly Wier.

“I think it was just a matter of time before it showed up in our treatment plants.” she said. Wier predicted an increase of carbaryl use this year, as homeowners spray more and more trees, and warned that being as careful as possible with the substance is an important “precautionary principle.”

“Any time we’re introducing a mass quantity of a fairly unknown chemical into an ecosystem, we have to see long-term effects,” she said. “We just don’t know enough about carbaryl.”

Because of its persistence throughout the entire spraying season, Bittner suspects the carbaryl that showed up in his treatment plant — which services Dillon, Silverthorne, Dillon Valley, Mesa Cortina and Wildernest — came from a careless commercial applicator, rather than from a homeowner. Last year, it had cleared up by the time the chemical had been identified. This year, however, Bittner will be ready for it.

“If it happens again, we should be able to trace it upstream,” he said.

A right way and a wrong way
As director of operations at Fort Collins-based Giving Tree Care, Inc., Dave Kunkel sprayed nearly 17,000 trees in the High Country in 2007. This year, he expects to treat between 25,000 and 28,000 in Summit County alone. When it comes to disposal of leftover insecticide, Kunkel cuts no corners.

“I do it by the book,” he said. After flushing his tank system with water, he sprays trees for free with the diluted solution. Once he’s finished with that step, he neutralizes the tank with a chemical degreaser, empties it into a 55-gallon drum, and disposes of it at a Larimer County hazardous waste company.

In Summit County, the Household Hazardous Waste Collection Program offers free disposal of small amounts of carbaryl and similar substances. According to Bittner, any container used for pesticides should be air dried, and never rinsed in a sink, toilet, storm drain, or gutter.

Although his training with insecticides gives him confidence in their safety, Kunkel acknowledges their limitations in fighting an infestation of such huge proportions.

“You can spray all day,” he said, “But I highly recommend people think about cutting down (infected) trees instead.”

Leftovers remain from 1980s epidemic
Twenty-five years ago, during the last beetle epidemic, ethylene dibromide (EDB) was used by the Forest Service on its property in Summit County to kill the insects. And unacceptable levels of the substance — banned by the Environmental Protection Agency in 1984 for most uses — showed up recently in a test well on the Frisco peninsula.

“(EDB) was the chemical of choice the last time the pine beetle came through,” said Dave Koop, Frisco’s water operations foreman.

According to Koop, wholesale spraying of EDB settled deep in the alluvial soil on the peninsula. The substance will eventually degrade naturally, but its continued presence after 20 years is a sobering reminder of potential effects of chemical use.

“I hope in treating this latest round of bugs, we haven’t caused new problems,” he added.

Harriet Hamilton can be reached at (970) 668-4651, or at hhamilton@summitdaily.com.

Carbaryl facts
An organic insecticide in use since 1958.
Product names include Sevin, Adios, Carbamec, and Slam.
Commonly used on apples, pecans, grapes, citrus, and asparagus.
Benign to birds, but acutely toxic to honeybees and aquatic insects.
For local disposal of carbaryl, contact Summit County’s Household Hazardous Waste Collection Program at (970) 468-9263.