Roadside spraying FAQs


Why does the County spray roadsides?
To control vegetation so the road area is free of obstructions, road users have sufficient view at curves and intersections and roadsides/culverts drain properly.

What roads does the County spray?  
See the County's annual Road Maintenance Program.

When is spraying performed?
Spraying is generally performed in spring, during the night. 

How is spraying performed?
A tanker truck drives along the road and sprays the road edge. 

Who performs spraying?
A contractor selected through a competitive bid process.

What products are used?
An approved mixture of Roundup Pro Concentrate (Glyphosate), a broad spectrum spray; Opensight (Metsulfuron methyl), a broad spectrum companion spray; EsplAnade 200 SC (Indaziflam), a pre-emergent; and Justified (modified seed oil), a drift control and deposition aid.

What rules govern roadside spraying?
Herbicide regulations established by the Oregon Department of Agriculture; other state and federal rules; and Washington County’s Integrated Vegetation Management Program (IVMP) and Best Management Practices for Routine Road Maintenance.

How does the County minimize environmental impacts?

  • Spraying only in priority locations (about 850 miles out of more than 2,500 miles of County road shoulders).
  • Spraying at night to reduce droplet drift and minimize exposure to the public.
  • Using a computer-assisted delivery system to control spray placement, mixture and application rate.
  • Spraying no more than 3 feet from the edge of the road.
  • Not spraying within 30 feet of stream and river crossings, and within 250 feet of streams with salmon or steelhead trout.

Can I opt out?
Yes. Find the “No Spray” Agreement section of the Right-of-Way Permits page. Submit the form online via the “right of way” section of the Public Permitting and Services Portal. You will need to post signs, which may be purchased from County Operations and Maintenance. For more information call 503-846-ROAD (7623) or email