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Facilities - Filter strip

Filter Strip

Filter Strip

A filter strip is a straight swatch of grass that removes sediment and oils from stormwater. Usually, filter strips are along edges of paved areas such as parking lots and roads.





Maintenance is needed if you see these signs

Bare, exposed soil

Clogged inlet and outlet pipes

Bottom of swale is eroded 

Sediment buildup, usually near inlet

Unhealthy or dead vegetation

Blackberries or other problem vegetation

Overgrown vegetation

Leaves, trash and other debris


Tips for fixing problems and general maintenance


Remove weeds such as blackberries and English ivy, then check for them on a regular basis and remove new vines.  Contact Clark County Vegetation Management for questions about controlling weeds at (360) 397-6140 or email 

Remove all trees and saplings that block facility elements.

Mow grass to keep height at 4 to 6 inches and remove clippings.

Replace vegetation damaged or removed during maintenance.

Avoid using fertilizers, herbicides, or pesticides within or near the facility.  These chemicals pollute the water and can cause unwanted plant growth.


Control erosion by reseeding areas where soil is exposed, especially on slopes.

Fill in eroded areas, and seed with grass.


Removing sediment is best done in dry months before winter rains set in.

If needed, seed and water during dry months to re-establish grass.


Pick up leaves before rains begin.

Inspect and remove debris regularly, particularly after storms.

Remove any material clogging drain, outfalls and channels.


Check roads and fencing in the facility.  They must be maintained to allow easy access.