The Clean Water Services  |  Tualatin, OR

Tualatin, Oregon Interceptor

Design-Build Interceptor

This progressive, design-build interceptor is a critical upgrade to a 42-year-old water system in Washington County, Oregon. The Clean Water Services (CWS) project is a major trunk feeding the Durham Advanced Wastewater Treatment Facility, which receives wastewater from the Sherwood and Bull Mountain areas.


CWS commissioned a planning study that identified deficiencies in the interceptor capacity, indicating it would need to be significantly increased in size. Kennedy Jenks worked with Shannon & Wilson and Aldea Services to prepare the design of the Tualatin River Crossing from King City to Tualatin.

Kennedy Jenks collaborated with contractors Mortenson Construction, K&E Excavating, and Michels Tunneling, who provided vital constructability and cost feedback to the design team. The design covered projected sewer capacity requirements, geotechnical conditions, seismic risk, constructability, maintainability, and stakeholder concerns to provide a long-term solution for CWS.

Phase A of the project included the most restrictive conveyance segment in the Interceptor, the King City Siphon, which would convey wastewater from a new River Terrace North Pump Station and surrounding residential areas across the Tualatin River. Selection of a micro-tunnel for the Siphon enabled construction without impact to the Tualatin River. The 650-foot vertical curve set a North American record for tightest vertical curve micro-tunnel of this diameter.

Phase B of the project included crossing State and City-owned roads, more than 30 privately-owned properties, a second Tualatin River Crossing, two constructed wetland crossings, two City Park crossings, and connection to CWS’ Durham wastewater treatment plant.

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Up next...

San Francisco Public Utilities Commission
Harry Tracy Water Treatment Plant
Seattle Public Utilities
Lift Station Evaluation and Design
Padre Dam Municipal Water District
Padre Dam
Palmdale Water District
Palmdale Regional Groundwater
Santa Clarita Valley Water Agency
PFAS Groundwater Treatment Project
Tesoro Viejo Master Mutual Water Company
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