Tualatin Basin Water Supply

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Design Concepts

Doing nothing is not an option.

In 2015, Reclamation and CWS began the engineering and environmental review of three key options at the existing dam and a downstream location:

  • Option 1, Modify Scoggins Dam:  Reclamation is leading the dam safety engineering and environmental review for modifying Scoggins Dam in its current location. This option provides a dam safety only modification without additional water supply benefits.
  • Option 2, Raise Existing Dam: Reclamation and CWS will be completing the engineering review for raising Scoggins Dam in its current location in conjunction with a dam safety modification. This option provides both dam safety and 21,000 acre feet increase in storage at the location of the existing dam.
  • Option 3, Downstream Dam: CWS is coordinating the engineering and environmental review of a proposed new roller compacted concrete dam downstream of the Stimson Mill. This option provides a 50,000 acre feet of increased storage at a new dam site and will include state-of-the-practice measures for dam safety.

Alternatives will be designed to withstand a major earthquake. Options 2 and 3 will also provide additional water. CWS is working closely with Reclamation's Dam Safety Office to coordinate the engineering and environmental reviews necessary to select a preferred alternative for design and construction.  A preferred alternative is scheduled to be selected in 2019.

Design concept 2: Existing Dam

Design concept 3: Downstream Dam