MOUNTLAKE TERRACE — It’s a green invasion that is pesky and stifling.
Folks living along the south shore of Lake Ballinger began noticing Eurasian milfoil in the fall of 2015. Two years later, the intruder had spread dramatically, creating dense weedy mats that cover much of the shore.
Now, the city of Mountlake Terrace and other jurisdictions are hoping to bring the Eurasian milfoil and two other non-native noxious weeds under control. The approach, which has involved seeking permits from the state Department of Ecology, could use a combination of herbicides as well as volunteer efforts to manually remove the weeds over several years.
A 2018 study found the Eurasian milfoil covering 16.8 acres of the lake; the fragrant water lily pads, 13.3 acres; and the curly leaf pondweed a little over half an acre. The lake itself covers about 103 acres. Inside the lake is 3-acre Edmount Island.
“With an infestation of that severity, options needed to be developed,” said Laura Reed, stormwater program manager for the city of Mountlake Terrace.
The invading plants are hurting native ones.
“The overly dense aquatic plant growth also greatly impairs habitat for fish and other aquatic species and negatively impacts water quality by increasing nutrient recycling and oxygen demand,” an environmental consulting firm wrote in its study of Lake Ballinger.
In 2018, Tetra Tech identified three non-native, noxious weed species in the lake. The Eurasian milfoil is designated as a Class B noxious weed by Snohomish County. That designation requires it be controlled.
The city was asked by local residents to look into the problem. It has worked closely with the Department of Ecology. Early on, the agency provided a $25,000 grant to map the aquatic plants in the lake and write a management plan.
Lake Ballinger is by no means alone.
“The Eurasian milfoil is an issue in a lot of our lakes,” said Colleen Keltz, a Department of Ecology spokesperson for water quality issues. “It’s all over Western Washington.”
A steering committee was formed to help Lake Ballinger. It included people from Edmonds and Mountlake Terrace, a representative from the nearby Nile Shrine Golf Course, and staff from both cities. The panel worked closely with Tetra Tech to come up with options.
The proposal is a combination of herbicides as well as volunteer efforts, such as cutting and raking as well as placing sand-filled burlap bags on the lake bottom.
The recommended herbicides are Fluridone and Florpyrauxifen-benzyl in low-dose applications over parts of the lake over several years. The Florpyrauxifen-benzyl would be used on 9 acres of milfoil in July or August; Fluridone would be used on fragrant water lilies and curly leaf pondweeds in August or September. The annual cost would be around $17,000, which would treat about half of the milfoil and a quarter of the fragrant water lilies and curly leaf pondweed in infested areas each year.
Reed said the herbicides were chosen because they are considered the least risk to humans and wildlife and would cause the fewest restrictions for fishing and swimming.
A survey of Hall Lake, upstream from Lake Ballinger, found variable leaf milfoil, an invasive considered a Class A noxious weed in Washington state. That designation requires it to be eradicated.
A public meeting to answer questions about the Lake Ballinger environmental issues is set for 7 to 8:30 p.m. May 29 at Mountlake Terrace Community Senior Center, 23000 Lakeview Drive.
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