Updates to a permit that helps remove noxious weeds

We work to prevent and reduce pollution and to clean up polluted waters. That's a simple summary, but sometimes it isn't that straightforward.

Specifically, we protect the quality of Washington's water so humans and aquatic life can use it for all of its many purposes. Whether that is a fish that spends its whole life in the water, a person who likes to swim in a river, or someone fishing for their dinner, there are many benefits that clean water provides.

Sometimes what is harming water quality isn't what people think of as typical "pollution" like chemicals or bacteria. Disease-carrying mosquitoes, invasive and noxious weeds, non-native fish, or invasive animals can impact both humans and aquatic life living in water. Non-native and invasive plants and animals can make it hard for native species to survive by using resources that native species need. Noxious weeds can clog waterways, making swimming and recreation activities difficult, and reducing native plant and animal habitat.

To protect water quality and control non-native plants and animals, the federal Clean Water Act and state law allow the use of some aquatic pesticides. This might seem counter-intuitive to our mission, but when used properly and following the regulations in our permits and the product labels, aquatic pesticides can be part of the solution. In some cases, a pesticide is the least damaging solution to protect water for shellfish harvesting, agriculture, habitat, and recreation.

So, what is a noxious weed?

A plant that causes economic loss or adverse effects to agriculture, natural resources, and human resources due to its presence and spread may be classified as a noxious weed. Noxious weeds in Washington are listed by the Noxious Weed Control Board. If an aquatic plant is listed as noxious, the Legislature requires Ecology to allow the use of aquatic herbicides to control the weed. An herbicide is a type of pesticide that targets plants and can prevent or disrupt normal plant growth.

Aquatic noxious weeds in Washington include many species such as Spartina, fragrant waterlily, Eurasian watermilfoil, and Zostera japonica (sometimes called Japanese eelgrass or dwarf eelgrass).

We have permits that allow aquatic pesticide and herbicide use in and around water to manage a target pest or weed that is causing problems and place conditions on the treatments to reduce risk to people and the environment. The permits meet state environmental protections and require special protections that go beyond the product label requirements (the use instructions on the product's container).

Zostera japonica - a noxious weed

One of our aquatic pesticide permits is specifically for the control of Zostera japonica. The Noxious Weed Control Board listed Zostera japonica as a noxious weed in 2012. This noxious weed is non-native and causes significant impacts on clam aquaculture and harvest for the shellfish industry in Willapa Bay in southwest Washington near South Bend. It is classified as a Class C noxious weed, the lowest category of noxious weed, that are generally present over a large area in Washington. Once Zostera japonica was listed as a noxious weed, commercial clam growers requested we issue a permit to allow the use of an aquatic herbicide for the control of the plant.

The permit, along with an Environmental Impact Statement, was first issued in 2014. We requested public comment on our work, and where appropriate, used those recommendations in our first final permit. We update general permits every five years, a process that includes public review of our proposed changes. We are now in the review process for this permit.

What does the permit allow?

The permit to control Zostera japonica using an aquatic herbicide is very limited. It is only for commercial clam growers in Willapa Bay and it does not apply to geoduck or oyster beds. The only herbicide allowed under the permit is imazamox. Registered by the U.S. Environmental Protection Agency (EPA) for aquatic uses, EPA categorizes this herbicide as a reduced risk pesticide (their lowest toxicity category), meaning any amount of imazamox found in or on food products is not considered a human health risk. Imazamox is only toxic to plants and is considered practically non-toxic to animals, fish, invertebrates, and other non-plant aquatic species.

Imazamox works by effecting a biochemical pathway in plants that is not present in animals. It is rapidly absorbed by the plant and degrades quickly, meaning there is a low risk of the herbicide persisting in the environment, moving off-site to affect non-target plants, or persisting in marine sediments. Based on our assessment of the characteristics of imazamox in the 2014 environmental impact statement and in a buffer validation study, we determined that use of imazamox is a low risk to non-target species when used according to the permit conditions and label requirements. A summary discussion of the buffer study is available in the permit fact sheet.

Protecting native eelgrass

Eelgrass, or sea grasses, are plants found in brackish or marine water that form highly productive ecosystems. They tend to stabilize sediment, and provide food, shelter, and nursery areas for many types of marine animals. Several permit requirements are designed to protect the important native eelgrass, Zostera marina.

These permit requirements include:

• Limiting the application rate of imazamox to no more than 1.4 ounces per acre, and only one treatment each year.
• Limiting imazamox application to wind speeds under 10 mph to minimize spray drift.
• Limiting imazamox applications to situations when there is at least one hour of dry time for the treated area before the next tide comes in.
• Prohibiting imazamox application in drainages that are flowing to areas containing the native eelgrass.
• Requiring at least a 10 meter buffer (about 33 feet) between treated areas and adjacent untreated property parcels.

More about buffer studies

Three buffer validation studies have been done. The first one was completed by staff from the University of Washington School of Aquatic and Fishery Sciences, who conducted their study before and after initial treatments with imazamox in May and June of 2014. Their final report was submitted to Ecology in 2015. Based on this report, Ecology modified the permit in 2017 to remove the requirement for further buffer studies, but visual monitoring of buffers around treated commercial clam beds is still required in some situations. This decision was based on the study results which showed no significant impact (>20% change in cover or stem density) to off-site Zostera marina in worst-case scenario treatments.

Confluence Environmental Company conducted another study in May 2015 on behalf of the shellfish growers to assess the impacts on nearby eelgrass one year after treatment. WSU Extension staff conducted a third study in May 2016 to assess the impacts two years after treatment. (Patten, 2016)

What changes are we proposing?

We're proposing the changes summarized below in the 2025 draft Zostera japonica permit. We're also proposing some minor updates to better organize the permit and to provide clarifications.

Changes in the draft permit include:

• Increasing the monitoring requirements to collect more consistent data about potential off-site impacts to adjacent eelgrass beds.
• An updated template for public notices and a Spanish translation of the notice. Final notices will be available on the on the permit webpage when complete.
• Notification requirements to post signage at nearby public access points and boat launches, and notify adjacent landowners about treatment.
• Moving the allowed treatment period from April 15 - June 30 to May 15 - July 31 each year.
• Updates to several sections about applying for, modifying, renewing, transferring, and ending permit coverage.
• Revised language about new electronic reporting requirements.

Do clam growers really need this herbicide?

By having a permit, we can protect water quality by adding specific conditions to the use of imazamox and requiring monitoring and reporting. Through the permit, we also require public notification when a clam grower applies for permit coverage. It is up to commercial clam growers to choose the approach that is right for them to manage this noxious weed. Our role is to make sure, as directed by the Legislature, there is an aquatic herbicide option available to clam growers in Willapa Bay that meets our water quality standards.

There are a number of ways to remove Zostera japonica, and using an herbicide is the only method that requires a permit from Ecology. Other methods are mechanical, such as harrowing or chain dragging. These methods are not regulated in this permit, and can also have serious environmental impacts, such as harming creatures that live in the sediment. A discussion of the various management options is included in the 2014 Environmental Impact Statement.

What areas are sprayed with this herbicide?

How much of Willapa Bay is treated with imazamox each year? Over the last five years, an average of 82 acres of clam beds have been treated each year.

The total area of Willapa Bay is around 80,000 acres, with approximately 8,000 acres covered by the native eelgrass Z. marina, and about 6,000 acres covered by the invasive eelgrass Z. japonica.

Treatment can only occur within Willapa Bay, at commercial clam sites that have permit coverage. The time of year for treatments is limited. In the past this has been between April 15 and June 30. The draft permit allows treatments between May 15 and July 31.

We invite your comments

We are accepting comments from Nov. 21, 2024, at midnight until 11:59 p.m. on Jan. 14, 2025. The draft permit and related materials are available on the permit webpage. Comments on the draft permit can also be submitted online or by mail as described below.

You can submit comments in the following ways:

• Submit comments online (preferred method)
• By mail:
  Shawn Ultican
  WA State Department of Ecology
  P.O. Box 47696
  Olympia, WA 98504-7696
• Verbal testimony, at a public hearing

Upcoming workshops and hearings

We are hosting two public workshops and hearings on the draft permit. At the workshop, we will explain the draft permit and answer questions. The hearing will provide an opportunity for the public to provide formal oral testimony and submit written comments on the draft permit. Oral testimony will receive the same consideration as written comments. The public hearing will begin immediately following each workshop and will conclude when testimony is complete.

• Online public workshop and hearing
  Dec. 30, 2024, 2 p.m.
  Register for the online meeting
• In person workshop and hearing
  Jan. 7, 2025, 6 p.m.
  Willapa Harbor Community Center - South Bend
  916 W First Street
  South Bend, WA 98586

Next steps

After the close of the public comment period, we will prepare a response to comments and describe any changes to the draft permit, and make a decision on permit reissuance. We expect to reissue the final permit by Spring 2025.

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