Officials share plan for using herbicides to control invasive weeds in Lake Ballinger this summer

Laura Reed, City of Mountlake Terrace stormwater program manager, listens to a question from a citizen Wednesday night. (Photo by Teresa Wippel)

About 30 people showed up at the Mountlake Terrace Community Senior Center Wednesday night to learn about a plan to remove invasive aquatic weeds from Lake Ballinger starting in July.

Located between Edmonds and Mountlake Terrace, Lake Ballinger is bordered by private homes, a City of Mountlake Terrace-owned park and the Nile Golf and Country Club. The majority of the lake is in located in Mountlake Terrace, so the city is taking the lead on the project, in partnership with the City of Edmonds.

The lake has in recent years become infested with invasive aquatic weeds, including Eurasian watermilfoil, fragrant water lilies, and curly leaf pondweed. The thick aquatic plant beds that cover most of the nearshore area have negatively impacted boating, swimming, and fishing in the lake, officials say. Invasive weeds have also reduced water quality.

Wednesday’s meeting was coordinated by City of Mountlake Terrace Stormwater Manager Laura Reed, who is managing the project. She talked with attendees about how to identify aquatic weeds, what local residents are allowed to do along their waterfront property without a permit but with permission from Washington Department of Fish and Wildlife, and tips for reducing the spread of aquatic weeds.

In addressing why it’s important to remove aquatic weeds from Lake Ballinger, Reed showed an image explaining the different types of lakes:

Oligotrophic lakes, such as mountain lakes, are “really clear, they have lots of oxygen, they don’t have a lot of algae,” Reed said, whiile mesotrophic lakes are “kind of in the middle. They have a few more plants, they’re a little bit more productive, they have a little less oxygen.” Eutrophic lakes, meanwhile, “are where Lake Ballinger is at,” Reed explained. “There’s a lot of nutrients coming in, there’s a problem with oxygen, we have a lot of weeds and in the past we’ve had algae blooms.”

The purpose of addressing weed issues in Lake Ballinger now is to avoid the hypereutrophic state, shown at the far right of the graphic, “which means that there is frequent, severe algae blooms and we have oxygen-deprived waters on a regular basis.”

Reed then explained the reasons for the increase in invasive aquatic plants and why they are a problem for the lake’s water quality. Nutrients enter the lake from various sources — such as pet waste, fertilizer and soils — in the entire 5,300-acre watershed surrounding 100-acre Lake Ballinger. Here’s a watershed map:

A map of the watershed.

“The plants love it. They pick it up in the water, they pick it up in the sediment, they thrive,” Reed said. Then, since the plants are all of one kind, they tend to die at once, “so you get a real demand for oxygen (required for plant decomposition) and then a real drop in oxygen levels,” which could trigger an algae bloom, she added.

Lake residents first began alerting city officials 15 years ago to the problem of invasive plant growth in Lake Ballinger, through their participation in the Lake Ballinger/McAleer Creek Watershed Forum. The group is made up of elected officials from the cities of Lake Forest Park, Edmonds and Mountlake Terrace, as well as concerned citizens, to address lake-related concerns.

Reed said she received a small grant from the Department of Ecology to hire TetraTech to bring scientific expertise to the issue. A steering committee was formed to take a closer look, and a draft plan to address the problem was created for public input.

A survey of plants in the lake confirmed that there was indeed a problem, Reed said. The following graphic indicates that fragrant water lily covers 13.3 acres and Eurasian milfoil 16.8 acres, with patches of curly leaf pondweed. Much of that is in shallow areas, where people are using the lake for recreational purposes.

The extent of aquatic plant coverage in Lake Ballinger.

“The recommended approach based on the study results was a combination of herbicides to control some of the massive areas where we have milfoil and fragrant lilies but also burlap bag barriers,” which can be used on private property to clear an area around a homeowner’s dock or waterfront, Reed said.

The steering committee also looked at other ways of removing the weeds, but found problems with them. For example, cutting and raking isn’t recommended for milfoil in particular, because it causes the weed to spread. Mechanical dredging is very expensive and it would be unlikely a permit would be issued for that, Reed said. Yet another idea was to introduce a type of fish — a grass carp — to eat the weeds but the problem is that they eat everything, including native plants, she explained.

The city then applied for, and received, a weed-control grant from the Department of Ecology to cover the application of an herbicide known as Fluridone. However, the plan was paused earlier this year when the city learned that a new herbicide, Florpyrauxifen-benzyl (otherwise known as ProcellaCOR), was scheduled to be approved by Department of Ecology and “could be very beneficial to this project” Reed said. By using ProcellaCOR, the city could get around the lake in half the time that was originally estimated, and it would also cut the cost, she said.

As a result of the new herbicide, the plan was revised to include applications of both Fluridone and ProcellaCOR, but for different purposes.

The map below shows the proposed treatment areas for each herbicide. The green striped area at the lake’s north end and the purple dotted area on the west side are where the city plans to apply the ProcellaCOR, targeted at milfoil. In addition, Fluridone will be used to target the lilies and curly leaf pondweed in the green striped area. Half the lake will be treated this year and the remainder will be treated next year, Reed said.

Proposed treatment area

Approved by both the Department of Ecology and the U.S. Environmental Protection Agency (EPA), fluridone has been around since the 1980s and works by interfering with a plant’s ability to photosynthesize, Reed said. A granular product, it was originally selected because it poses the least risk to humans and wildlife, and there are no restrictions on irrigation, fisheries, swimming or water contact after application.

The herbicide will cost $9,050 to treat 25 percent of the lake shallows area, she said.

ProcellaCOR — a spray product which is only used to treat milfoil — was approved by the EPA in 2017 and is scheduled to be approved by the State Ecology Department on July 5. If for some reason it is not approved, the city won’t use it, she noted. ProcellaCOR tends to kill plants quickly — within one or two weeks — by speeding up plant growth and elongating plant cells. It also poses the least risk to humans and wildlife and with no restrictions on irrigation, fishing, swimming or other water contact.

It will cost $6,240 to treat 50 percent of the lake with ProcellaCor.

Reed noted that the city has applied for Washington State Department of Ecology permit to treat the lake this summer with the two herbicides. A public comment period on that application is now open and runs through June 10. Comments may be submitted to Department of Ecology, Water Quality Program, Attn: Aquatic Pesticide Permit Manager, by either email at
or via mail at PO Box 47600, Olympia, WA 98504-7600.

If the permit is issued, applications will be made three separate times via an airboat on the lake this summer — at the end of July, in the middle of August and after Labor Day

Citizens will see is an airboat like this on the lake during the application period.

The city plans to review the results of this summer’s work and make any necessary changes based on those results, she said. These include sampling to determine how much of each herbicide is left after each application, Reed said, noting that the herbicides do break down quickly. There will also be plant surveys during the process and after the applications, to see the results.

All the residents on the lake have received a letter from the city notifying them of the intent to apply the herbicides, Reed said. In addition, 24 to 48 hours before any herbicide is applied, all the shoreline properties will be posted by the herbicide applicator.

Reed also spent some time talking Wednesday night about ways that lakefront residents could control aquatic weeds around their own property. One of those methods involves taking sheets of burlap and covering the plants, which essentially smothers them. The sheets can be weighted down to the lake bottom with sandbags, and a plan will be developed for the City of Edmonds to provide the sand for this process. Homeowners must provide their own burlap, however. Homeowners can also hire their own divers to remove the weeds, she said.

The project is funded by grants for the first two years, but a longer-term strategy needs to be developed to get rid of the invasive weeds and prevent them from coming back, Reed noted. One option could be to create a local improvement district, similar to the effort that was created to fund maintenance of the weir (basically a low dam that regulates water flow) on the lake.

The City of Edmonds will be leading the planning for long-term solutions, Reed said.

The eventual goal is for the lake to have a diversity of plant life, with an emphasis on native species, which will ensure its health, she added.

— By Teresa Wippel



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