Cougar Reservoir is a 450-foot high earth filled dam located on a tributary of the Willamette River in western Oregon. The US Corps of Engineers intends to make major modifications to the intake tower to allow selective reservoir withdrawals at multiple elevations.

In order to construct these tower modifications with minimum impact to the reservoir purpose (flood control), the Corps contracted with Tetra Tech INCA to design major modifications to a diversion tunnel that was originally used for dam construction, but subsequently plugged. INCA’s work included the design of an underground valve chamber and a tunnel/channel lining for the existing access tunnel so it could be used for both access as well as serve as a conveyance channel for very high velocity water released from the dam.

 Cougar Lake Diversion Tunnel (121.36 kB)

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