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Cougar hydropower

Generators / total output two 25 mw

Cougar project data

Dam length 1,600 ft 487.7 m
Height 452 ft 137.8 m
Elevation (NGVD*) 1,700 ft 518 m
Lake length 6 mi 9.7 km
Area when full 1,280 ac 518 ha
*National Geodetic Vertical Datum

Contact us about Cougar:
General: 541-684-4300
Recreation: 541-942-5631

Email us about Cougar

Cougar pamphlet

Cougar Dam & Reservoir

Cougar Dam

Cougar Dam and Reservoir is located at River Mile 4.4 of the South Fork McKenzie River, about 42 miles east of Eugene, Ore. It is a rockfill structure with a gated concrete spillway that was completed in 1963 at a cost of $54.2 million. Since then, it has prevented about $452 million in potential flood damages. Cougar Lake has a storage capacity of 219,000 acre-feet and controls runoff from an area of 208 square miles.

Cougar Dam works in coordination with Blue River Dam for the purpose of flood risk management. Cougar Dam’s authorized primary purposes are flood risk management, hydropower, water quality improvement, irrigation, fish and wildlife habitat and recreation.

Cougar recreation

Birding: The project encompasses almost 5,000 acres and the uplands are managed primarily through an agreement with the Willamette National Forest.  The reservoir is a designated stop along the Three Sisters section of the Oregon Cascades Birding Trail. This Trail is a self-guided auto tour of nearly 200 prime birding destinations in the Oregon Cascades.  American peregrine falcons have been observed around the cliffs above the lake.

CampingRecreation facilities at Cougar are operated by the U.S. Forest Service. Call the McKenzie River Ranger office at 541-882-3381 or click one of the links for more information: Echo day-use area; Slide Creek Campground; Sunnyside Campground; French Pete Campground; or Delta Campground.

Environmental stewardship at Cougar Dam

The project encompasses almost 5,000 acres and the uplands are managed primarily through an agreement with the Willamette National Forest. To mitigate impacts of Corps dams on Chinook salmon and resident fisheries within the McKenzie River basin, the Corps built the McKenzie Hatchery. The Oregon Department of Fish and Wildlife maintains and operates the hatchery with funds from the Corps of Engineers and the State of Oregon.

In 2004, the Corps completed a temperature control tower for Cougar Dam, which improved downstream conditions for threatened fish species. Currently, the Corps is operating a new fish ladder and holding facility below the dam that allows biologists to collect adult fish from the river and transport them upstream to their natal streams.  The Corps also promotes resident fisheries throughout the McKenzie River basin through the continued support of Leaburg Hatchery and as a partner in efforts to recover bull trout and Oregon chub within the McKenzie River drainage.

Cougar Adult Fish Collection Facility

aerial view of the adult fish collection facilityBiologists estimate the habitat above the dam once supported more than 4,000 returning adult spring Chinook. Original construction included both adult and juvenile fish passage facilities to help move fish past the dam. However, due to the dam’s impact on downstream river temperatures, adult fish no longer migrated to its base. The Corps abandoned the original adult and juvenile fish passage facilities because they proved to be ineffective.

In combination with the Cougar Dam Temperature Control Tower, this new $10.4 million collection facility supports a complete fish life-cycle over long stretches of the South Fork McKenzie River by moving adult fish to high quality spawning habitat above the dam. Fisheries biologists believe this will substantially support recovery of endangered fish populations in this Willamette River sub-basin.

The facility includes a fish ladder leading from the base of the dam to a fish collection and sorting area. From there, adult salmon, bull trout and other resident fish are loaded onto trucks and transported to release locations above Cougar Reservoir. The facility’s design incorporates the best features of trapping facilities at other locations, including Bonneville Dam and the Cowlitz River in southern Washington.

The Corps operates and maintains the facility according to guidelines developed collaboratively between the Corps, Oregon Department of Fish and Wildlife and other agencies. ODFW determines which fish species, and how many, are moved above the dam for natural spawning. ODFW biologists are on site daily conducting research and monitoring during operational months of May through October, when spring Chinook enter the South Fork McKenzie River.

Returns of wild adult spring Chinook salmon to the trap since it opened in 2010 have ranged between 250 and 525. We expect similar returns in the future until a long-term solution is implemented to help improve survival of juvenile salmon attempting to pass the dam on their way downstream from their spawning grounds to the ocean.

Cougar Temperature Control Tower

The Corps modified the dam’s intake tower by adding adjustable weir gates and a wet well. The new features allow dam operators to selectively draw water from various depths of the reservoir and mix it to a temperature more closely matching pre-dam downriver conditions.

Total cost of the project from pre-construction work in 1999 to completion in 2005 was $50.5 million. The first phase of the construction began in June 2000 when the diversion tunnel used to redirect the river during initial dam construction was excavated, reinforced and gated. The diversion tunnel was opened in April 2003, drawing the reservoir down to about one-third its normal size to allow the south face of the intake tower to be fitted with its new wet well and adjustable weir gates.

Total cost of the project from preconstruction work in 1999 to completion in 2005 was $50.5 million. The first phase of the construction began in June 2000 when the diversion tunnel used to redirect the river during initial dam construction was excavated, reinforced and gated. The diversion tunnel was opened in April 2003, drawing the reservoir down to about one-third its normal size to allow the south face of the intake tower to be fitted with its new wet well and adjustable weir gates.

There are three vertical slots running almost the full length of the face of the wet well, each with a set of three overlapping weir gates. Since water temperature within a reservoir changes with increasing depth, the gates can slide up and down as needed to create openings at various levels in the lake. Water drawn in through the openings is mixed to the proper temperature in the wet well and then routed through the penstock to the powerhouse or regulating outlet downriver.

Wild adult spring Chinook salmon began returning to the South Fork McKenzie River almost as soon as the temperature control tower came on line. Returns to the new adult fish collection facility downriver of the dam since it opened in 2010 have ranged between 250 and 525. We expect similar returns in the future until a long-term solution is implemented to help improve survival of juvenile salmon attempting to pass the dam on their way downstream from their spawning grounds to the ocean.

Cougar Portable Floating Fish Collector

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.

Drawing of the Cougar Dam Portable Floating Fish CollectorDrawing of Cougar Dam Portable Floating Fish Collector

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.

Getting around

  

Flood risk management at Cougar Dam

Conservation season - April to November: None.
Flood season - November to March: Replace wire ropes and restrict pool to 1671 feet.

For more information, visit our Water page.