Removing Zostera japonica from Willapa Bay Commercial Clam Beds
In Washington, we're fortunate to have a beautiful coastline that provides a place for recreation, habitat, and has great economic benefit. At Ecology, our Water Quality Program works to prevent and reduce water pollution and to clean up polluted waters. That’s a nice simple summary, but it isn’t quite that straight forward.
We work within the structure of the federal Clean Water Act and the state’s Water Pollution Control Act to do our work. Part of regulatory work is to permit and limit pollution from operations or activities that could pollute water. This often comes in the form of a National Pollutant Discharge Elimination System (NPDES) permit to limit the amount of pollutant discharge allowed from industrial or municipal facilities to levels that protect water quality.
Part of our role in protecting state waters is protecting the benefits these waters provide. The Clean Water Act and state law allows the use of aquatic pesticides for the purpose of protecting the benefits that waters provide. This might seem counter-intuitive to our mission. But, when used under the limits of our permits, aquatic pesticides can be part of the solution to protecting water that is used for all different purposes, including shellfish harvesting, agriculture, habitat, and recreation. Pesticides can be used to control:
- Disease-carrying mosquitoes
- Weeds and algae in lakes, rivers, and irrigation systems
- Invasive and noxious weeds
- Invasive aquatic animals
- Non-native fish
Controlling a noxious weed
A plant that causes economic loss or adverse effects to agriculture, natural 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.
To remove the weeds and allow people to use water for recreation and other uses, while protecting water quality, we have aquatic pesticide permits. Our permits conditionally allow aquatic pesticide and herbicide use in and around water to manage a target pest or weed that is causing problems. The permits meet the state environmental protections and require special protections that go beyond the product label requirements (the use instructions on the product’s container).
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). 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. 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.
Zostera japonica – a noxious weed
Zostera japonica has thinner blades than our native eelgrass.
We generally update and reissue our general permits every five years and it is now time for us to update the Zostera japonica permit. We're accepting comments on updating this permit from Sept. 18, 2019 until 11:59 p.m. on Nov. 4, 2019. More details on the comment period are below or on the permit web page.
How does a general permit work?
A general permit is a type of permit that regulates a number of different businesses, based on similar discharge characteristics, under one permit. All of those who are doing similar work that result in the specific discharge allowed by the general permit may apply to be covered under the permit. If each applicant meets the requirements of the permit they are granted conditional authorization to discharge. The permit holder must follow the requirements in the permit. Failure to follow requirements can result in enforcement action by Ecology or litigation brought by third parties.
When commercial clam growers apply for coverage under the permit, we review the application to determine if the applicant meets the permit requirements. For example, the applicant must be a commercial pesticide applicator licensed by Washington Department of Agriculture. The applicant must also have a sponsor for the application. The sponsor is the individual who has authority to manage a specific parcel containing a commercial clam bed and determines what management methods are appropriate for their clam bed, including the use of herbicides for the control of Zostera japonica.
What does the permit allow?
Only one herbicide is allowed under the permit, imazamox. Registered by 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. It works by effecting a biochemical pathway in plants that is not present in animals. Imazamox 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 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 the permit conditions and label requirements. A summary discussion of the study is available in the 2017 permit modification fact sheet.
What changes are we proposing?
We're not proposing any significant changes to the permit during this update. Minor updates have been made to better organize the permit and to provide some clarification. In 2017, we modified the permit based on additional research done on the buffers required by the permit and a desire to protect offsite native eelgrasses. The results of the studies show that a 10 meter buffer will protect the nearby native eelgrass. The 2014 permit was modified in 2017 to continue allowing the use of imazamox and to finalize the buffers in the permit.
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 can also have serious environmental impacts, such as harming creatures that live in the sediment. 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 that can be used and meets our water quality standards. A discussion of the various management options is available in the 2014 environmental impact statement.
Mat of Z. japonica growing at the water's edge
Do clam growers really need this herbicide?
By having a permit, we can be protective of water quality by adding specific conditions and requiring monitoring and reporting. Through the permit, we also require public notification for when a clam grower applies for permit coverage.
What areas are sprayed with this herbicide?
Treatment can only occur within Willapa Bay, at sites that have permit coverage. The time of year is limited to between April 15 – June 30.
The potential area to be treated is currently no more than 1,200 acres of commercial clam beds. This is:
- 1.6% of the total area of Willapa Bay (77,000 acres)
- 4.6% of the tidelands that could contain eelgrass (26,000 acres)
- 20% of the 6,000 acres designated for clam culture in Willapa Bay
However, on average much less is treated. During the previous permit cycle an average of 22 acres were actually treated. This is:
- 0.3% of Willapa Bay
- 0.85% of estimated tidelands
- 3.7% of acres designated for clam culture
We invite your comments
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 the 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.
The workshops and hearings will held :
Oct. 21, 2019 starting at 1 p.m.
Online webinar hearing
Join for the webinar
Oct. 22, 2019 starting at 1 p.m.
In-person hearing
Willapa Harbor Community Center
916 W First Street
South Bend, WA 98586
Copies of the Draft Permit and Fact Sheet: The draft permit and fact sheet are available on the permit webpage. You may also request copies of these documents from Jon Jennings, at jonathan.jennings@ecy.wa.gov, or 360-407-6283.
We are accepting written comments from Sept. 18, 2019 until 11:59 p.m. on Nov. 4, 2019
Comments should reference specific permit text when possible.
Make your comments online via the eComment form (preferred method), or
By mail:
Jon Jennings,
WA State Department of Ecology
P.O. Box 47696
Olympia, WA 98504-7696
Next steps
After we review the feedback we receive on the draft permit and related materials, we will update our work, prepare a response to comments, and make a decision on permit reissuance. We expect to have a decision by early 2020.