Aquatic Plant & Algae Management General Permit

We issue the Aquatic Plant and Algae Management (APAM) General Permit to allow chemical treatments for the management of aquatic noxious weeds, native nuisance plants, and algae. These chemicals are limited to a specific list of aquatic-labeled herbicides, algaecides, biological water clarifiers, adjuvants, marker dyes, shading products, and phosphorus sequestration products. They can be used directly into fresh water (lakes, streams, and rivers) or along shorelines, roadsides, dikes/levees, and ditch banks.

The current permit went into effect on April 21, 2021, and expires on March 21, 2026.

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We've updated our sign template to use more icons to help applicators warn people about any restrictions. 

Current permit documents

Permit reissuance

The public comment period is now closed for the draft permit. We are reviewing and considering all comments received. We will develop a final draft of the permit based on comments and publish an official Response to Comments as an appendix to the factsheet. A final decision on permit issuance is expected early 2026.

Changes we are proposing

  • Revising monitoring requirements around dissolved oxygen and some types of treatments to reduce phosphorous
  • Clarifying treatment timing windows and the process to modify them
  • Increasing flexibility around when some aquatic herbicides can be used, based on more detailed ecotoxicity data
  • Adding one aquatic herbicide and a lanthanum-based phosphorous control product
  • Updating permit language to be consistent with current state and federal laws

Note: An addendum to the existing supplemental EIS that includes information on these products is being prepared and will be finished prior to issuing the final APAM permit.

Public involvement

We provided public notice of the draft general permit (WSR 25-17-084), published a blog with some highlights of the proposed changes to the permit, and accepted public comments from Sept. 10 through Oct. 24, 2025. We hosted two public meetings and formal hearings on October 14 and 16, providing opportunity for formal spoken testimony on the draft permit. Ecology received comments online, by mail, and during our public hearing. 

Permittee resources 

Permit documents

View and download permit documents.

Washington Department of Fish and Wildlife's Aquatic Pesticides Map Tool (Treatment Timing Windows)

Map shows specific locations where use of aquatic herbicides is subject to different timing restrictions to protect fish and other priority species. Click image to go to WDFW's map.