Steel Lake's aquatic weeds eradicated


The Mirror

Steel Lake property owners’ goal to control the growth of aquatic weeds in the popular lake over the next 10 years looks like it’s been fulfilled about nine years ahead of schedule.

After creating its own lake management district —  the first in the city — residents with lakefront property around Steel Lake announced last week they won their first battle against Eurasian milfoil, a non-native aquatic weed that has taken over the lake in years past.

Last year, lakefront property owners agreed to form a lake management district and tax themselves to raise money to control outbreaks of the aquatic weed, which is frequently transmitted by boat from other infested lakes and grows from just a fragment of a piece of the plant.

Milfoil doesn’t have any natural predators here, city Surface Water Management division staff said, and once it finds its way into a lake or body of water, it grows unchecked, creating mats of vegetation that can choke out other aquatic growth and render a popular lake unusable for boating, swimming or fishing.

In one summer, the Steel Lake lake management district has treated five acres of milfoil, as well as 1.3 acres of fragrant water lily, another invasive aquatic plant. While milfoil is completely eradicated, the lake management district intends to preserve 25 percent of the water lilies, which are a native species.

When they created the lake management district, the committee of lakefront property owners established a rate structure based on a 10-year budget to cover underwater surveys, chemical plant control, a few minor equipment purchases and on-going public education and outreach.

Owners of single-family property around the lake pay $85 a year to cover the costs of managing aquatic weeds and the city pays $2,048 for the portion of Steel Lake Park that abuts the lake. The state, which owns the boat launch, pays $3,500 and owners of multi-family housing pay $275 annually.

During an aquatic weed survey at Steel Lake conducted after a contractor applied the herbicide 2,4-D DMA, no milfoil plants were found, said Don Robinett, the city’s Endangered Species Act and National Pollution Discharge Elimination System coordinator and the staff person helping with the lake management district. The National Pollution Discharge Elimination System is part of the national Water Quality Protection Act.

During a more recent survey, a surveyor found only a single plant, Robinett said.

Before the lake management district formed, city staff used a combination of herbicide and hand-pulling to control outbreaks of milfoil, but it wasn’t effective enough, Robinett said. While hand-pulling works well for some types of plants, it doesn’t work well for milfoil because hand-pulling itself can fragment the plant, which is how it propagates.

Last year, the lake management district decided to go for an all-herbicide treatment. While 2,4-D has been under investigation as a potentially dangerous chemical, Robinett said the lake management district is using “the one that’s not so controversial.”

The lake management district intends only to use the herbicide as needed. Since there isn’t any milfoil to speak of this year, the lake management district won’t have to pay a contractor to come in and apply it, Robinett said. And with the money they’ll save, the lake management district will target outbreaks of yellow flag iris, another aquatic problem at the lake.

Robinett said he didn’t know if the milfoil herbicide would have a harmful reaction with other herbicides used in the lake, but he did note no wildlife or fish eat milfoil.

On the other hand, allowing milfoil to grow unchecked could prove harmful to life in the lake. “When plants grow so densely, they increase the nutrient loading in the lake, which can impact oxygen quantities,” he said.

Angela Storey, a spokeswoman for the Washington Toxics Coalition, said although 2,4-D is a commonly used herbicide, “it’s by no means a benign chemical.” She noted 2,4-D is a possible carcinogen with potential impacts on endocrine and reproductive development, and could pose a risk to pregnant women, children and adults with compromised immune systems.

Robinett said all the herbicides used in Steel Lake have been fully reviewed and approved by the Department of Ecology.

Still, there are lake use restrictions at the time the herbicide is applied, he said. Lakefront property owners are warned against using lake water for irrigation or other secondary uses for 96 hours, and there’s a 24-hour swimming advisory in the areas where the herbicide has been applied.

Robinett pointed out that doesn’t mean people can’t swim anywhere in the lake. “If the lily pads have been treated, don’t go swimming through the lily pads,” he said.

The lake management district issues a standard notification 10 days before the herbicide is applied. Robinett said he hand-delivered notices to people living around the lake himself, and city Surface Water Management staff emailed people who live near the lake and posted advisories on the boat launch and in the swimming areas.

Storey said the Washington Toxics Coalition has done quite a bit of work treating milfoil without using herbicides. “There are so many alternatives available to control milfoil and water lily,” she said, noting house boat owners on Lake Washington have been happy with harvesters used to control milfoil, and others have had some success controlling — though not eradicating — the aquatic weed by hand-pulling.

Robinett said in addition to applying the herbicide as needed, Steel Lake property owners will continue their fight against milfoil by providing boater education. “It’s going to be a constant battle,” he said.

Staff writer Erica Hall: 925-5565,

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