Columbia Boulevard Wastewater Treatment Plant Support Facility

Projects / Oregon / Built in 2013 /

Site Context and Challenge:

Located adjacent to the rich habitat of the Columbia Slough, a remnant of historic wetlands between the Sandy and Willamette Rivers, Portland’s Columbia Boulevard Wastewater Treatment Plant (CBWTP) is Oregon’s largest water treatment facility. Serving 614,000 customers, the plant operates around the clock to treat an average of 80-90 million gallons of sewage daily through a complex series of mechanical and biological processes. While most infrastructure buildings are located out of the public eye and are not designed for visitors, the CBWTP sits directly on the 40-Mile Loop, a trail system connecting the City of Portland to a long stretch of the Columbia River that passes through both industrial and ecologically rich areas. To embrace this context, the project had to shift the paradigm of how city infrastructure typically relates to the urban fabric and the public it serves.

Design Strategy:

In 2010 the plant operator, Portland’s Bureau of Environmental Services (BES), began a design process to develop the new LEED Gold-rated Columbia Building to house the plant’s engineering staff. The landscape architect on the design team lead both the client and architect in an exploration of potential opportunities incorporating the broader context, including creating an ecological connection to the adjacent Columbia Slough, preserving and repurposing historically significant spaces, and incorporating public amenities and educational features into the design.

Native Landscape and Artful Stormwater

The front entry of the Columbia Building is encircled by a diverse mix of native slough grasslands, linking the building site to the natural areas to the north and east. A planted berm at the front of the building transitions the building’s geometry to the surrounding grassland areas, burying the south side of the building to a depth of 7-feet to shield it from the harsh southern sun and the noise of the adjacent railroad tracks. The grasslands continue to the roof of the building in a move away from traditional sedum ecoroofs.

An entry plaza features stormwater runnels that extend from the diversely planted roof down into infiltration basins, providing educational opportunities for visitors and highlighting water movement through the site. The plaza is adjacent to a new bicycle trail that connects the Columbia Building Project to the 40-Mile Loop Trail. Geometrically arranged, live-stake native plantings buffer the entry drive and campus perimeter, anchoring the facility in its environmental context. Bioswales treat run-off from the parking area while runnels channel stormwater from the faceted green roofs, carrying water to a series of infiltration basins that recharge groundwater at the slough. Biofiltration swales were oversized to divert water from existing parking areas, effectively removing over 50,000 square feet of paved area from being diverted directly to the river.

Historic Landscape Preservation and Repurposing

During the design process, the landscape architect encouraged a fundamental move toward rerouting the main vehicular circulation away from the historic axis and core to the exterior perimeter of the new building. This decision allowed the center of the campus, with its mature ornamental trees and lawn, to be reclaimed as a pedestrian sanctuary for plant employees and visiting school children. From the open glazing of the lobby, the northern view is aligned with the historic roadway axis and provides an initial view into the formal central green. A new circular pathway unifies the space and at times floats above tree roots to avoid damaging them. Mature ornamental trees were preserved on the site despite the vast infrastructure improvements that were required for the new building. The central pathway terminates into a 22’ diameter culvert, a remnant from Portland’s Big Pipe Project, a massive infrastructure project that diverts combined sewer overflows away from the nearby Willamette River. The culvert creates an outdoor classroom that integrates interpretive graphics about the plant and its connection to the surrounding ecosystem.


Merging site and architecture, the Columbia Building showcases technical and natural water processes in a highly visible and creative way, while maintaining necessary security measures. Sustainable systems such as diverse native plantings, recycled irrigation water, an innovative grassland ecoroof system, gravel infiltration basins, and biofiltration swales were integrated throughout the design. The landscape architect linked the project to the surrounding plant by eliminating vehicular traffic from the plant’s core and connecting the facility to nearby bicycle trails. The project explores educational opportunities at all levels, including visual downspouts that display stormwater movement, remnant pipe segments that explore the client’s larger role in the region, and other interpretive elements throughout the site.

Project Title: Columbia Boulevard Wastewater Treatment Plant Support Facility
Entrant office name: Studio
Role of the entrant in the project: Landscape Architect
Other design firms involved:
Skylab Architecture, Design Architect
John Grade, Artist
Biella Lighting Design, Lighting Design
The Felt Hat, Visual Communications

Project location: Portland, OR.
Design year: 2011
Year Built: 2013


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