Chemicals resurface in sewer system

SILVERTHORNE — A toxic chemical commonly used to kill pine beetles has shown up again in wastewater treated at the Silverthorne/Dillon Joint Sewer Authority, officials reported this week.

Last summer, routine testing at the treatment facility revealed the presence of carbaryl — an insecticide also known as Sevin — in effluence draining into the Blue River.

Because of concerns about the chemical’s possible impact on the river’s delicate ecosystem, the sewer authority started a stringent monitoring schedule for this year’s pine-beetle spraying season.

Two samples taken on different dates in May tested positive for carbaryl, plant manager Mike Bittner said.

Although amounts of the pesticide were small — 6 parts per billion in the test sample from the plant’s intake — any measurable level at all indicates illegal disposal of the chemical.

“This is not the stormwater system,” Bittner said. “It shouldn’t get into the sanitary sewer system.”

May’s positive result triggered further testing designed to trace the origin of the dumping. Samples were collected from several sites throughout the system, and the town of Silverthorne issued a press release warning of legal penalties and possible fines amounting to more than $2,000 for disposing carbaryl in sewer drains.
“If it’s a willful act, there will be criminal penalties,” Silverthorne utilities manager Zach Margolis said.

Although the five follow-up samples all tested negative for the pesticide, the plant’s beefed-up monitoring schedule will continue throughout the spraying season, Margolis said.

An organic insecticide commonly used in the commercial cultivation of food crops such as apples, citrus and grapes, carbaryl is generally benign to birds, but acutely toxic to honeybees and aquatic insects.

As part of Colorado’s designated Gold Medal trout stream system, the stretch of the Blue River next to the treatment facility is home to a trout population dependent on healthy numbers of aquatic insects. Any carbaryl runoff could be devastating to the river’s ecosystem.

“The bugs are so sensitive to it,” Margolis said. “That’s what makes it a good bug killer.”

The treatment processes used by the sewer authority do little to remove the chemical, he added. Once it’s in the system, it will eventually find its way into the Blue River.
Margolis expressed surprise that the carbaryl resurfaced this year despite the town’s community-education efforts.

“When we took our flier over to Bighorn Materials, they took all the carbaryl products off their shelves,” he said by way of example.

This type of problem isn’t confined to pine-beetle insecticides, High Country Conservation Center director Carly Wier observed.

“It goes to the ‘out-of-sight, out-of-mind’ idea,” she said. “We think the problem is gone away when we’ve poured it down the drain, but it never goes away. We have to deal with it eventually.”

Even disposing toxic chemicals such as carbaryl in the garbage may cause problems in the long run, she added.

“If it goes in the landfill, carbaryl might show up in the soil 30 years later.”

Which is what happened recently on the Frisco Peninsula, when unacceptable levels of ethylene dibromide (EDB) — a chemical used by the Forest Service during the 1980s pine-beetle epidemic and banned by the EPA in 1984 — showed up in a test well.

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.

Concentrated cleaners and all flammable chemicals should receive similar treatment, Wier added.

“These substances deserve great caution,” she said.

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