Irrigation System Aquatic Weed Control General Permit - NPDES

What is the purpose of this permit?
This permit allows those who have coverage to apply aquatic herbicides into irrigation canals to control weeds and algae. This permit helps Ecology:
  • Mitigate and condition the use of chemicals that may enter the aquatic environment.
  • Track pesticide rates and use locations.
  • Ensure that notifications and postings occur in areas where the public or local residents may access the treated areas.
Who issues this permit?
Department of Ecology
What activities require this permit?
Irrigation systems that use aquatic herbicides in irrigation canals where water flows to a point of compliance are required to have coverage under this general permit. To find out the specific activities that trigger this permit, go to the Irrigation System Aquatic Weed Control General Permit website and click on "Fact Sheet."
How much will this permit cost?
There is no fee to apply for permit coverage. Once covered, however, there is an annual coverage fee. For FY 2016, the annual permit fee is $522 while the FY 2017 fee is $550. You will be billed for permit fees after permit coverage is issued. Please see for the current permit fee schedule.
Where can I get the application for this permit?
The application is called 'Irrigation System Aquatic Weed Control Permit - Application for Coverage' is online and can be accessed at
Do I need to include anything with my application?
In addition to the permit application, the applicant must submit maps with the boundaries of the irrigation system, points of compliance (Permit Section 4) and pesticide application locations (Permit Section 5). A completed and signed State Environmental Policy Act (SEPA) checklist is also necessary unless SEPA is completed at the local level. If SEPA is completed at a local level, include a completed and signed SEPA determination with your permit application. The forms for SEPA are available here:
Is the decision on my permit dependent on anything besides the information in my application?
When making the decision on your permit, Ecology will consider the applicable laws and rules, the contents of your application, and the background environmental conditions.

In addition, the permitting process includes public participation. This means that the public may submit comments to Ecology during the 30 day public comment period to support or oppose your proposed activity. If any comments are received, Ecology must review and respond to the comments and take them into consideration when making the decision to issue or deny permit coverage.
How long will it take to review my application?
See the Permit Timeliness Results above for average processing times. New permittees must submit a complete application form at least 90 days prior to the planned activity that will result in the discharge to waters of the state. Permittees with an existing permit must reapply for coverage at least 180 days prior to the expiration date of this permit. The current permit expires June 15, 2017. See for details.
Where do I submit my application?
Department of Ecology
Water Quality Program
Attn: Irrigation Permit Manager
PO Box 47600
Olympia, WA 98504
How long is my permit valid?
Ecology general permits are issued for a 5 year period. The current permit expires June 15, 2017. Permits may be administratively extended past their expiration date for a period of five years. Permittees must apply for permit renewal at least 180 days prior to the permit expiration date in order to be covered by the extended permit. The conditions of an extended permit remain in effect and are enforceable. An extended permit may not be modified.

Coverage may be cancelled before the end of the 5 year period by submitting a Notice of Termination or for failure to pay your yearly permit fee. Coverage should only be cancelled if the pesticide discharge you are permitted for is no longer going to occur.
What is the appeal process for the permit?
You, or a third party, have a right to appeal permit coverage to the Pollution Control Hearings Board (PCHB) within 30 days of the date of receipt of the letter authorizing coverage. Appeals are limited to the general permit's applicability or non-applicability to a individual discharger (WAC 173-226-190(2)). The appeal process is governed by Chapter 43.21B RCW and Chapter 371-08 WAC. "Date of receipt" is defined in RCW 43.21B.001(2). To appeal, you must do the following within 30 days of the date of receipt of this letter:
  • File your appeal and a copy of the permit cover page with the PCHB (see addresses below). Filing means actual receipt by the PCHB during regular business hours.
  • Serve a copy of your appeal and the permit cover page on Ecology in paper form - by mail or in person (see addresses below). E-mail is not accepted.
You must also comply with other applicable requirements in Chapter 43.21B RCW and Chapter 371-08 WAC.     Mailing Addresses:     Pollution Control Hearings Board     PO Box 40903     Olympia, WA 98504-0903     Department of Ecology     Attn: Appeals Processing Desk     PO Box 47608     Olympia, WA 98504-7608     Physical Addresses:     Pollution Control Hearings Board (PCHB)     1111 Israel Road SW, Suite 301     Tumwater, WA 98501     Department of Ecology     Attn: Appeals Processing Desk     300 Desmond Drive SE     Lacey, WA 98503
Notes / Comments:
Please contact Ecology early in the process so that we may assist you with understanding requirements for this permit.
Legal Authority:
Permit Timeliness Results

Permit Timeliness data collection is in response to a State Auditor’s Performance Audit and RCW 43.42A. Each regulatory agency developed a plan to improve permit clarity, predictability, and timeliness. Each agency considers the customers experience to ensure permit assistance is simple to use, easy to access, and designed in a customer-friendly manner. Agencies report progress to the Governor’s Office for Regulatory Innovation and Assistance (ORIA). ORIA prepares and distributes reports, with participation from the State Auditor’s Office and Results Washington. See latest report here:

All permits submitted for reporting were entered into this Regulatory Handbook. Here are the results of the performance data:

Estimated Time Required By the Agency to Process a Permit Application (Definition)
Average number of days from Receipt to Complete: 4
Maximum number of days from Receipt to Complete: 4

Estimated Time Required By the Agency to Issue a Permit Decision (Definition)
Average number of days from Complete Application to Decision: 46
Maximum number of days from Complete Application to Decision: 46

(Summary results based on 1 submittals in 2015, no data for current year)

Where can I get permitting assistance?
Web page URL:
Subject matter expert phone: Irrigation System Aquatic Weed Control General Permit
Department of Ecology
300 Desmond Drive
PO Box 47600
Olympia, WA 98504-7600
Telephone: (360) 407-6000
Triggering Questions:
  • Are you an irrigation district that plans to use aquatic herbicides to control weeds and algae in irrigation canals?
* Permit information last updated 8/21/2023