CB 121161 — Version 1 https://webapi.legistar.com/v1/seattle/Matters/16838/Texts/18178 CITY OF SEATTLE ORDINANCE __________________ COUNCIL BILL __________________ ..title AN ORDINANCE relating to the Cedar River Municipal Watershed; amending the Secondary Use Policies, adopted by Ordinance 114632, to provide for the limited application of the herbicide imazapyr to treat invasive knotweed species; and ratifying and confirming certain prior acts. ..body WHEREAS, the Cedar River Watershed Secondary Use Policies, adopted by Ordinance 114632, include a moratorium on herbicide use to prohibit the routine broadcast application of herbicides for control of roadside vegetation in lieu of brushing, and noxious weeds were not a consideration in watershed land practices when these Policies were adopted in 1989; and WHEREAS, in 2010 uncontrolled knotweed covered 18 acres in the Cedar River Municipal Watershed, displacing native plants, eroding stream banks, threatening water quality, and spreading rapidly without effective means of control; and WHEREAS, on August 6, 2010, a limited exception to the Secondary Use Policies was authorized by Ordinance 123365 to allow the application of the herbicide imazapyr to control or eradicate knotweed species in the Cedar River Municipal Watershed through December 31, 2012, providing Seattle Public Utilities an efficient and cost-effective control strategy for the first time; and WHEREAS, imazapyr inhibits an enzyme found only in plants, and the U.S. Environmental Protection Agency rates imazapyr as being relatively non-toxic to birds, mammals, fish, and invertebrates, and a Washington State University toxicologist found the risk to water quality to be nil; and WHEREAS, four follow-up limited exceptions to the Secondary Use Policies were authorized by Ordinances 124191, 124852, 125813, and 126850 to continue to allow application of the herbicide imazapyr through December 31, 2015, 2018, 2021, and 2025, respectively; and control efforts have successfully reduced knotweed coverage, resulting in the reduction of herbicide use per acreage in the Cedar River Municipal Watershed; and WHEREAS, routine maintenance treatments on known patches and annual surveys for new patches in sensitive areas continues to be the most effective way to minimize herbicide use and costs, and it is widely accepted that the ecological risk of small amounts of imazapyr is significantly less than the ecological risk of uncontrolled knotweed; and WHEREAS, Seattle Public Utilities is legally required to control knotweed on the Cedar River and its tributaries and a long-term management strategy maintains Seattle Public Utilities' compliance with noxious weed regulatory law and is consistent with King County Noxious Weed Program's best management practices for knotweed control; NOW, THEREFORE, BE IT ORDAINED BY THE CITY OF SEATTLE AS FOLLOWS: Section 1. Cedar River Watershed Secondary Use Policy 6-13, last amended by Ordinance 126850, is amended as follows: Seattle Public Utilities will continue the herbicide moratorium, controlling undesirable vegetation with hand or mechanical methods, except that the following exemption for the use of imazapyr shall apply through December 31, ((2025)) 2031. Seattle Public Utilities is authorized to apply imazapyr to control or eradicate knotweed species within the Cedar River Municipal Watershed according to the methods and procedures established in this section and all applicable state and federal drinking water source protection standards. Seattle Public Utilities will adhere to targeted foliar application methods that use a one percent imazapyr solution applied directly to knotweed leaves with backpacks or handheld sprayers. Herbicide will be applied by licensed pesticide applicators. Seattle Public Utilities will monitor knotweed treatment areas annually and will monitor water quality before and after herbicide application. Seattle Public Utilities will provide the ((Transportation and Seattle Public Utilities Committee)) Governance and Utilities Committee or successor committee an annual report on the knotweed treatment program in the Cedar River Municipal Watershed, summarizing the effectiveness of the knotweed treatment program, evaluating the long-term financial and environmental implications for knotweed control beyond ((2025)) 2031, evaluating water quality monitoring results, summarizing the latest available science on the environmental and human health effects of imazapyr, and describing any plans for the future use of imazapyr within the Watershed, including maps of proposed treatment areas, estimated quantities of imazapyr to be applied, application methods and schedules, and plans for water quality monitoring. Seattle Public Utilities may authorize use of imazapyr to newly-discovered areas of knotweed infestation, but use on newly-discovered areas located within the hydrographic boundary may not exceed five acres in size. Section 2. The General Manager and CEO of Seattle Public Utilities shall ensure areas formerly occupied by knotweed are restored to native vegetation. Section 3. The General Manager and CEO of Seattle Public Utilities shall continue the ongoing program for monitoring, detecting, and controlling noxious weeds in the Cedar River Municipal Watershed with a goal of preventing colonies of knotweed from re-establishing. Section 4. Any act consistent with the authority of this ordinance taken after its passage and prior to its effective date is ratified and confirmed. Section 5. This ordinance shall take effect as provided by Seattle Municipal Code Sections 1.04.020 and 1.04.070. Passed by the City Council the ________ day of _________________________, 2026, and signed by me in open session in authentication of its passage this ________ day of _________________________, 2026. ____________________________________ President ____________ of the City Council Approved / returned unsigned / vetoed this ____day of _______________, 2026. ____________________________________ Katie B. Wilson, Mayor Filed by me this ________ day of _________________________, 2026. ____________________________________ Scheereen Dedman, City Clerk (Seal) Zoe Loutos SPU Knotweed ORD D1a 2 Template last revised December 16, 2025 2 Version No. 1