Lake Stevens may be treated with herbicide to control milfoil

LAKE STEVENS — The best solution to get rid of the Eurasian water milfoil taking over Lake Stevens is to use an herbicide.

That’s what a 6-0 vote of the Lake Stevens City Council decided Monday, following a committee’s recommendation to use a treatment of the herbicide triclopyr to rid the lake of the aquatic weed.

Eurasian water milfoil has invaded the shoreline of the nearly 1,100-acre lake. Residents living around the lake told city officials at a public meeting in August that the weed gets stuck in the motors of boats and can potentially tangle up swimmers.

A committee met several times to consider options to treat, manage or eradicate the weed. Seven types of herbicide treatment were considered, according to public works director Mick Monken.

Triclopyr was the top recommendation because it only affects water milfoil and not other aquatic plants. The herbicide would eradicate the milfoil and is approved by the state Department of Ecology, Monken said.

“The herbicide dissolves and disappears, it doesn’t stay in the water,” Monken said. “It’s not made to kill creatures, mammals, fish, waterfowl. It’s designed for water milfoil.”

The cost of the herbicide treatment over a period of 10 years is estimated to be $520,000 with the most expensive portion, at $186,000, occurring in the first year.

The city is in the process of applying for a $75,000 grant from the Department of Ecology to help with the treatment. The city will submit the aquatic weed management plan to the department for approval and then begin the process of satisfying state Environmental Policy Act requirements. The herbicide could be applied to the affected areas in the lake in May, Monken said. During the second year of treatment, divers will administer spot treatments and remove leftover water milfoil by hand.

Swimmers could be allowed to use the lake after 24 hours of the application, according to Monken.

“The target for the city and the community is let’s not go through another year like this,” he said.

Amy Daybert: 425-339-3491; adaybert@heraldnet.com.

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