Portsmouth Force Main

LOCATION:  Oregon   |   OWNER:  City of Portland Bureau of Environmental Services
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Cost: $50 million

The City of Portland’s Bureau of Environmental Services entered into a combined sewer overflow abatement agreement with the Oregon Department of Environmental Quality. The final phase of this program is the three-mile-long (4.8 km) Portsmouth Force Main, which will control the remaining outfalls on the Willamette River.

McMillen Jacobs Associates performed preliminary and final design as part of the Brown and Caldwell Team.

We used an extensive alignment analysis process to arrive at the preferred alternative as part of the preliminary design work and considered different construction methods as we refined final alternatives. Factors examined in the selection process included operations, risk, constructability, third-party impacts, and costs. A public outreach component was vital to this analysis process and was used to gather input from key stakeholders in the project area and identify traffic concerns for some of the area’s more significant businesses. An additional alignment alternative was identified because of the extensive input provided by these crucial stakeholders, and was reviewed and later adopted as part of the preferred alignment. This resulted in lower project costs and minimized impact on business and traffic in the most congested portions of the project area.

The project consists of approximately 16,000 feet (4,877 m) of wastewater conveyance comprising 6,000 feet (1,829 m) of conventionally excavated soft ground tunnel, 2,500 feet (762 m) of large-diameter, 84-inch (213 cm) microtunnel, and 7,500 feet (2,286 m) of open-cut construction. McMillen Jacobs Associates was responsible for tunnel and trenchless design, shaft design, cost estimating, management of the geotechnical investigation program, and preparation of the geotechnical baseline report.