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The City of Portland, Oregon

Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Ave, Suite 613, Portland, OR 97204

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Southwest Stephenson Street Roadside Swales


Completed this spring, the SW Stephenson project has transformed 2,760 feet of roadside ditches into swales between SW 35th and SW Boones Ferry Road.  This project was designed to improve water quality in Oak, Arnold, and Tryon Creeks by directing stormwater runoff into roadside swales where pollutants can be filtered prior to entering the creeks.  In addition to improving water quality, the project has improved pedestrian safety along SW Stephenson by adding four-foot wide shoulders.

At the intersection of SW Stephenson and SW 27th Ave, Environmental Services worked with Portland Bureau of Transportation to replace a storm drain with a green street planter.  The planter not only filters and slows runoff, but it also improves pedestrian safety at the busy intersection next to Stephenson Elementary School.  Pedestrians are also able to use the widened paved shoulders instead of the middle of the road for jogging and dog-walking.

SW Stephenson and SW 27th Ave: Before (above) and after (below)

The ditches on SW Stephenson quickly carry stormwater runoff to Tryon Creek and its tributaries causing erosion and transporting pollutants. The swales were designed to slow the runoff to reduce erosion. The native grasses and plants not only stabilize the soil, but they also help to filter pollutants from the road.  The result is cleaner rivers and streams, and a healthier watershed.

Ditches along SW Stephenson: Before (above) and after (below)




Add a Comment


Kristan Burkert

August 17, 2016 at 8:52 AM

What actually is the difference between the ditch and the swale (second set of pictures)? The lush spring vegetation in "before" hides topography, so it is hard to tell. What is engineered?


Matthew Burlin

August 18, 2016 at 12:56 PM

Great question, Kristan. The lush spring vegetation in the "before" photo is a bit deceiving because it does not show the conventional maintenance activity of scraping the ditch out for conveyance capacity, which exposes bare soil resulting in sediment being transported downstream to Tryon Creek. The goal of the engineered swale is to slow the water down with check dams and to have rushes and other low growing plants filter pollutants.

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