The dam’s temperature control tower helps closely mimic pre-dam downstream water temperatures, but poses serious challenges for endangered juvenile spring Chinook salmon trying to migrate out to sea. All water passing Cougar Dam must flow though the tower, but flow conditions at the corner of the reservoir where the tower is located make it hard for fish to find and enter it. Passage efficiency and survival rates of those that do manage to enter the tower are not high enough to support a self-sustaining wild Chinook population.
The project delivery team working on downstream passage options at Cougar Dam identified the most likely solution as a surface collector that attracts and holds juvenile Chinook until they can be transported around the dam. However, the team realized that there were too many data gaps to make an informed decision about design.
The portable floating fish collector is a small-scale experimental fish collector to help inform the decision-making and design of a future permanent downstream passage solution.
The PFFC is a large pump-driven intake and collection structure surrounded on three sides by a floating hull moored vertically to the reservoir bottom in four places, and anchored horizontally by cables extending to the dam face and adjacent hills. The collector’s pumps generate an attraction flow of about 100 cubic feet per second.
It is equipped with a PIT tag detector and other equipment to help determine how efficient it is at collecting fish. The PFFC will also provide valuable information about the operations and maintenance requirements for whatever permanent solution is ultimately decided upon – debris loading, maintaining moorage in a fluctuating reservoir, daily boarding and operations, etc.
A few utilities use large-scale collectors as permanent fish passage solutions, but only at reservoirs that fluctuate up to about 50 feet. No small-scale collector built to stand a 180-foot reservoir fluctuation like Cougar’s then existed.
The Corps contracted engineering firm HDR and naval architects at Art Anderson Associates to design the PFFC. Cherokee Construction Services built and assembled it.