Columbia Slough Regional Stormwater Treatment Facility

Where does the rain go? It has to go somewhere, and in Gresham stormwater runoff must be managed to prevent flooding, erosion and pollution from flushing into public creeks, streams, rivers and watersheds.

Columbia Slough Regional Stormwater Treatment FacilityAn Urban Wetland

Finished in 2008, the Columbia Slough Regional Stormwater Facility treats stormwater runoff from 965 acres of nearby industrial development before it is discharged to the Columbia Slough, and provides wetland habitat for local wildlife and educational tours for school groups.

What is Stormwater Runoff?

Stormwater runoff is a carefully watched environmental issue in Gresham. As the city has grown, parking lots, buildings, sidewalks, and driveways have replaced vegetated areas where precipitation such as rainfall and snowmelt can soak into the ground. As a result, less rain soaks in and "runoff" from these hard surfaces is generated.

How the Stormwater Site Works

The stormwater runoff from the commercial development is piped to the site by creek and pipe. Once it reaches the constructed wetland, the water is filtered through various levels of vegetation, leaving behind the pollutants it picked up on the way such as heavy metals, oil and grease, and sediments. As the water wends its way through the constructed wetland these pollutants are removed en route to the treated water discharging into the Columbia Slough. The Boeing Company's generous land donation of 14 acres made this project possible.

A Pacific tree frog. Photo by Fred Small, Pacific Habitat ServicesWildlife Loves It

The Columbia Slough Regional Stormwter Treatment Facility has been transformed from acres of invasive blackberries to a constructed wetland that not only treats polluted water, but provides a home to native plants and wildlife. The water quality site is filled with native plants such as rushes, sedges, cotton wood and dogwood trees, and wildlife including more than 26 different types of songbirds, hawks, frogs, rabbits, and coyotes. More than 10,000 trees and plants were installed to create the constructed wetland.

Caring for the Slough

The Columbia Slough is a 60-mile long remnant of lakes, wetlands and slow-moving channels that run through the heart of major industrial and commercial sections of Gresham and Portland. Impacts from development and urban stormwater carrying pollutants has led to degraded water quality throughout the basin. Gresham worked with the Columbia Slough Watershed Council on the design of the water quality site.

A Place to Learn

Map of Location 

This facility was designed with a trail loop and interpretive panels to allow teachers to take students on a self-guided tour. Backpacks of educational materials that meet fourth grade learning benchmarks are available at the Wastewater Treatment Plant main office, along with a key to the site access gate. To schedule an appointment to pick up the key and materials call 503-618-3450. You may also want to combine your visit with a field trip to the Wastewater Treatment Plant.

  • Oregon’s Public Works Stormwater Project of the Year 2008; presented by the Oregon Chapter of the American Public Works Association
  • Columbia Slough Watershed Council Achievement Award 2007 for Outstanding Contribution to the Columbia Slough