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Lake Oswego – Tigard Water Partnership Structures

The Lake Oswego – Tigard Water Partnership was an expansive, nine-year-long effort to create a new water supply system for the two cities. In addition to more than 10 miles of large-diameter pipeline, the project included several major structural components. OBEC served as a specialty structural engineering for three major structural projects.

The River Intake Pump Station (RIPS) is a critical piece the system that draws water directly out of the Clackamas River. A major component of this project was a 68-foot-long pipe bridge that connects the off-shore structure to the shoreline. The bridge supports a 46-inch-diameter welded steel pipe and includes an innovative shear key foundation system to prevent the tower from overturning during seismic events.

The Waluga Reservoir 2 (WR2) is a new 3.5 million gallon (MG) prestressed concrete reservoir situated in a heavily-wooded neighborhood in Lake Oswego on property adjacent to the existing 4MG Waluga Reservoir.

The Bonita Pump Station (BPS) provides an initial operating capacity of 14MGD, with the capability of expanding in the future to 20MGD. The BPS was designed to serve the Tigard 410 Pressure Zone, and may also be designed to serve both the Tigard 410 and 470 Pressure Zones through separate and parallel pumping systems and discharges.

Services Provided

  • The utility bridge portion of the RIPS is constructed to provide maintenance access to the intake tower and is designed to support mobile cranes large enough to pick the 50-foot-tall pump assembly in one piece through the tower roof.
  • The BPS was equipped with a flow bypass to allow Tigard to supply water back to Lake Oswego during emergency conditions.
  • The design team worked closely with LOTWP throughout design to meet stringent permitting and land use requirements, and helped support a robust public involvement effort, which defined design criteria and project aesthetics.