A new plan for dealing with the environmentally degrading, obstructive, and, in some cases, invasive aquatic plants in the lakes and canals in Ocean Shores was presented to the public Feb. 1.

Public comment on the Integrated Aquatic Vegetation Management Plan, developed for the city by water resources consulting firm AquaTechnex, will be incorporated into the firm’s final draft of the plan, which will then be delivered to the Ocean Shores Fresh Waterways Advisory Board.

The plan will advise the city on how to manage water weeds over the next few years, said Ocean Shores City Administrator Scott Andersen.

Terry McNabb, a representative from AquaTechnex, visited the Ocean Shores Convention Center Wednesday to summarize results from vegetation surveys conducted on Ocean Shores waterways and outline pros and cons of different treatment options.

“There are a lot of different types of technologies you can use to deal with aquatic vegetation problems, and people have opinions about them, and that’s kind of what we want to capture,” McNabb said.

This Integrated Aquatic Vegetation Management Plan is the city’s third since 1994. Over the course of the last three decades, aquatic vegetation has posed a problem for fresh waterways in Ocean Shores, both in ecological health and for human use. While the type of species of problematic plants — and means of control — have shifted over the years, the benefits of keeping them in check have remained consistent: a less-restricted path for boaters and recreators, ecological health including habitat for fish, and a more appealing feature for tourists.

And aquatic health is of special interest for many whose backyards blend with the city’s 23-mile fresh waterway system, which includes Duck Lake and a series of interconnected canals.

According to McNabb, about 59% of the 482 acres of freshwater in Ocean Shores have aquatic vegetation at “problematic” levels. Since aquatic plants can only grow where sunlight reaches, they tend to concentrate in the shallower canals rather than the depths of Duck Lake, McNabb said.

Historically, an invasive plant called Brazilian Elodea — commonly found in aquariums, not to be confused with the native elodea plant — filled the city’s fresh waterways. According to the Washington Invasive Species Council, the plant was detected in Duck Lake in the early 1990s, and the city responded with a non-chemical approach, stocking grass carp with hopes the fish would devour the plant. Later, after supplemental chemical treatments, the city controlled the plant.

“We saw almost no Brazilian Elodea,” McNabb said of recent surveys.

Elodea plants are still largely present in the system, according to a Fresh Waterways Advisory Board Report from 2022, as are Azolla and Parrot’s feather plants.

”Parrott’s feather is something we think you should be concerned about,” McNabb said. “If you let it go, it will totally dominate the system.”

The city treated a “past large parrot’s feather location in the extreme northern wetland portion of the Grand Canal,” in 2022, reducing it to a “minor” infestation, according to the advisory board’s report.

Parrot’s feather, along with Azolla, can form large mats on the water’s surface, restricting boaters and blocking sunlight.

The city’s vegetation management plan will provide a treatment strategy for the city moving forward. McNabb presented a few potential strategies, saying the most effective plan would likely be a combination of herbicides and mechanical treatment.

While a few grass carp still remain in the lake, more could be planted as a means for biological control, McNabb said. The fish are relatively cheap, and usually “reduce the problem, but probably never get rid of it,” McNabb said.

Harvesting — or cutting out weeds with machines — is another non-chemical treatment McNabb presented. The Ocean Shores Fresh Waterways Corporation, a nonprofit that assists with vegetation projects, owns a harvester, and has made it available to the city in the past, according to corporation President Bruce Malloy. The harvester was retrofitted in 2005 and is currently “effective,” according to Grant Schaffer, a member of the city’s Fresh Waterways Advisory Board.

Malloy and Schaffer said there is a plan to “resurrect the harvester to help with our weed problems while saving the city some money on this expenditure.”

McNabb said the cost of harvesting depends on how far the harvester is forced to travel to dump vegetation on the bank.

According to Andersen, the city council has budgeted $315,000 over the next two years for aquatic plant management. That includes $110,000 for harvesting operations in 2023 and $75,000 for harvesting in 2024.

The rest of the money is allocated for herbicide treatment, Andersen said. Two common herbicides — Diquat and Fluridone — kill plants by reducing their ability to photosynthesize. The city used Diquat treatments in 2022.

The Washington Department of Fish and Wildlife uses Diquat to treat fungus in fish hatcheries.

At the Feb. 1 presentation, several residents expressed concern about the effects of herbicides on fish and human health. McNabb explained that because water is a three-dimensional medium, allowing for greater movement of chemicals, aquatic herbicides are subjected to a harsh review process by the Environmental Protection Agency.

“The EPA has a battery of tests that prove it’s not going to impact fish, it’s not going to impact drinking water supply, those types of things,” McNabb said.

McNabb said ProcellaCOR, a recently-approved herbicide, is “extremely effective” on Parrot’s feather and Eurasian milfoil, another prevalent plant. The herbicide is selective, meaning it won’t harm other vegetation.

Unlike past vegetation management plans, the city’s new plan will consider harmful algae blooms. Algae booms result in foul smelling waters, and can be toxic in some cases.

According to the advisory board’s 2022 report, Fishhook Canal is the “most problematic” for algae issues system-wide. Based on samples taken by algae buoys, McNabb said the canals had “extensive levels of phosphorus, and that’s the thing that’s driving these harmful algae blooms.”

McNabb said hydrogen peroxide is a common treatment for algae blooms, such as in the California Aqueduct.

Andersen said the city plans to develop an algae management plan, which would be a part of the overall aquatic management plan.

Other than the city’s budget, funding for treatment could come from Department of Ecology grants, which distribute money to municipalities that rely on lakes in one way or another. Grant revenue comes from a $3 fee on the annual registration of boat trailers, which are the biggest vector of aquatic invasive species, according to Ecology.