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Road Services - Roadside weed control

About the Weed Control Program

Road Services annually schedules its roadside weed control program for the unincorporated areas of the county and in some cities by contract. As part of the program, licensed technicians perform controlled herbicide spraying along some road shoulders starting in the spring and going through the summer. The spraying is performed to help reduce safety hazards for pedestrians, motorists and bicyclists. The spraying also controls noxious weeds that are toxic to some animals and pose environmental risks to native vegetation.


The Seattle-King County Health Department monitors the Roads Maintenance Spray Program for potential environmental health impacts and has been very pleased with the results of tests on herbicides applied using the division's application methods.

All herbicide applications are designed to keep roads and shoulders safe for motorists, bicyclists and pedestrians, prevent root systems from damaging the roadways and to reduce sod buildup that can cause roadway flooding and icy conditions in the winter months. Weed control also reduces fires that can ignite uncontrolled vegetation and overgrowth that can cause accidents due to reduced visibility.

Road Services uses small amounts of herbicides on a carefully-controlled basis. Trained and licensed technicians use only those herbicides approved by the United States Environmental Protection Agency, Food and Drug Administration and the State Department of Agriculture. These technicians must take required annual certification refresher courses to maintain their license prior to performing any of the herbicide spraying. Applications are additionally guided by best management practices that include follow-up monitoring and soil testing.

No routine herbicide spraying is conducted in ditches or near water, including rivers, streams, wetlands, bridge abutments, guardrails near water, levees, backslopes or in moratorium zones, which includes the Snoqualmie Valley and both Vashon and Maury Islands. Although, noxious weed control, which law mandates, can include spot spraying even in moratorium areas.

Road Services will also be removing all tansy ragwort from the right-of-way due to the flowering weed’s danger to animals. State and local laws require the removal of tansy ragwort and other noxious weeds. Residents who maintain the right-of-way are asked to place vegetation that may contain tansy ragwort in sealable bags to prevent the spread of this weed.

"Owner Will Maintain" Program

King County offers residents the opportunity to participate in a companion program to the Roads Maintenance Spray Program. The "Owner Will Maintain Program" allows residents to control vegetation on the right-of-way that abuts their property. To participate in this program, residents must sign a maintenance agreement with the county to maintain the right-of-way and to also post "Owner Will Maintain" signs in an area visible from the roadway.

Maintenance agreements may be obtained using the "No Spray Request Form" (74KB .pdf) or by calling 206-296-8100 or toll-free by calling 1-800-KC-ROADS. The maintenance agreement must be completed and returned to Road Services before an "Owner Will Maintain" sign can be issued. The signs are provided to property owners at no charge. To continue participation in this program, residents must complete a new agreement and submit it to Road Services annually.

Related links


Visit our glossary for an explanation of common road terms and jargon.

Contact us

King County Road Services Division
Traffic and Road Maintenance Section
155 Monroe Ave. N.E.
Renton, WA 98056
1-800-KCROADS (1-800-527-6237)
206-296-8198 (fax)

Also see: Additional contact information

Information from the Road Services Division's website is available to people with disabilities in alternate formats upon request by calling 206-477-3839 or 711 for the TTY relay service.

External link = External link

2015 No Spray Request Form

Download, print and complete the 2015 No Spray Request and Property Owner/King County Maintenance Agreement Form:

›› 2015 No Spray Request Form (74KB .pdf)

Return the completed form to:

King County Road Services Division
Traffic and Road Maintenance Section
155 Monroe Ave. N.E.
Renton, WA 98056

If you have any questions about the Herbicide Vegetation Control Program or the No Spray Request and Property Owner/King County Maintenance Agreement Form, please contact us using the information provided at the bottom of this page.