Cedar Mill Creek

Project Description

On its way to its confluence with Beaverton Creek, Cedar Mill Creek flows through Tualatin Hills Nature Park, a 222-acre nature and wildlife preserve managed by the Tualatin Hills Parks & Recreation District (THPRD). A 40-year-old sanitary sewer pipe in need of replacement flowed underground through the preserve, and THPRD recognized an opportunity to combine ecological restoration with the improvement of aging infrastructure. As ecological experts on a team led by Mortenson, Biohabitats collaborated with Clean Water Services to divert Cedar Mill Creek during the infrastructure repair and restore its natural flow in a way that enhanced its function and habitat.

Biohabitats began by performing a site survey and establishing an access road to reach the site with minimal impact. After salvaging fish, Biohabitats diverted and dewatered the creek using temporary bypass channels. After the sewer was excavated, Biohabitats restored the creek, adding side channels as well as instream and floodplain wood structures for additional habitat complexity. The wood structures were created using trees felled during the creation of the access road. Other construction work included grading of wetlands, installing and maintaining erosion and sediment controls, stockpiling felled trees and brush, hydroseeding with a bonded fiber matrix, planting thousands of native plants, restoring and enhancing trails, and conducting post-construction monitoring and reporting.

Completed on time and within budget, the project not only improved wastewater infrastructure and thus regional water quality, but also local habitat and ecology.