Wilsonville Wastewater Treatment Outfall Replacement

The City of Wilsonville is set to embark on a project to replace a 40-year-old corrugated metal outfall pipe and install a new diffuser at the Wastewater Treatment Plant.


The project provides increased wastewater treatment capacity to accommodate future growth, improves Willamette River water quality and satisfies Oregon Department of Environmental Quality (DEQ) compliance requirements.

Leakage from the outgoing outfall pipe was discovered in 2014; the City completed interim repairs on the outfall in 2015.

The Wilsonville City Council approved preliminary design and permitting or the replacement pipe in October 2015, and authorized final design and bid support in November 2016. In May 2018, Council authorized a contract with Northbank Civil and Marine to complete the $1.1 million replacement and diffuser installation.

When completed, the improved system is capable of providing wastewater discharge capacity up to 7 million gallons per day.