Irrigation System Aquatic Weed Control permit

The Irrigation System Aquatic Weed Control (ISAWC) permit allows the regulated use of aquatic pesticides, marker dyes, and nutrient-inactivation products to control the growth of aquatic plants and algae within irrigation systems, helping them to maintain the capacity to convey water.

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The Irrigation System Aquatic Weed Control permit was last issued in 2012 and is currently under administrative extension.

Current permit documents

Permit reissuance

The administrative extension allowed us to develop an environmental impact statement (EIS) to assess permitted chemicals allowed for use within irrigation systems and to identify mitigation actions to reduce the potential of adverse environmental impacts. 


January 2023 – March 20, 2023: Formal comment period on the draft permit and Environmental Impact Statement
July 2023: Anticipated decision on reissuance
August 2023: Anticipated effective date for the final permit

We initially invited comments on the draft Irrigation System Aquatic Weed Control permit and Environmental Impact Statement beginning Jan.18, 2023, until 11:59 p.m., March 6, 2023. We extended the deadline for comments until 11:59 p.m., March 20, 2023, in response to stakeholder requests. 

We will publish a response to comments as an appendix to the fact sheet to address comments submitted during the public comment period. 

 Irrigation canal passing through fields in Roza Irrigation District

Comment period

The comment period was open Jan. 18 – March 20, 2023. We collected comments online, by mail, and during our public hearings.

Comments are available for viewing through our online comment form.

Workshop and hearings

During the workshops in late February, we explained the proposed changes to the permit and environmental impact statement and answered questions. The hearing began immediately following the public workshop. 

View the Irrigation System and Aquatic Weed Control workshop and hearing presentation

Apply for coverage

Due to the current administrative extension of the permit, no new applications for coverage will be accepted until the permit is reissued.