Portland, Oregon NE Siskiyou Green Street Project Report

In 2003, the Portland Bureau of Environmental Services installed two landscaped stormwater curb extensions designed to capture street stormwater runoff on Siskiyou Street in Portland, Oregon. Essentially disconnecting the street’s runoff from the City’s combined storm/sewer system, the Siskiyou curb extensions manage it on-site using a landscape alternative. The objective was to maximize the capture, treatment, and infiltration of street stormwater runoff, while enhancing the neighborhood and offering improved pedestrian safety.

The project only took two weeks to complete, required no modifications to the stormwater collection system, left the existing street curb intact, and only cost $17,000. The NE Siskiyou Green Street curb extensions converted 590 square feet of pavement into green landscape. The curb extensions include a series of mini-dams. Water cascades from one “cell” to another within the dams until the curb extensions reach storage capacity. The Green Street can manage 225,000 gallons of stormwater runoff per year.

The project on Siskiyou was the first retrofit to an existing street in Portland. Environmental Services built a second set of curb extensions on Ankeny Street (at SE 56th) in 2004, and by 2005 both the City and private developers were implementing a number of similar projects.

Green Streets has since become a comprehensive city-wide program - in 2007 the City Council approved a Green Streets resolution, report, and policy prepared by an inter-agency committee which promotes the use of green streets in private and public development. By the end of 2010, approximately 950 green street facilities had been constructed. 

ASLA - the American Society of Landscape Architects - chose the NE Siskiyou Green Street project for a general design award in 2007.  ASLA describes the functionality in detail: “Stormwater runoff from 10,000 square feet of NE Siskiyou Street and neighboring driveways flows downhill along the existing curb until it reaches the 7-foot wide, 50-foot long curb extensions…The landscape system in place infiltrates water at a rate of 3 inches per hour. If a storm is intense enough, water will exit the landscape area through another curb cut at the end of each curb extension and will flow into the existing street inlets. With the new stormwater curb extensions now in place, nearly all of NE Siskiyou’s annual street runoff, estimated at 225,000 gallons, is managed by its landscape system. In fact, multiple simulated flow tests have shown that the curb extensions at NE Siskiyou Street have the ability to reduce the runoff intensity of a typical 25-year storm event by 85 percent.”

Portland’s Green Street Program is a sustainable stormwater strategy that meets regulatory compliance and resource protection goals by using a natural systems approach to manage stormwater, reduce flows, improve water quality and enhance watershed health.




Publication Date: 2007

Related Organizations:

  • Portland, Oregon Bureau of Environmental Services
  • City of Portland, Oregon

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