News Release
| Release Number: | 00-114 |
| Dated: | 6/22/2000 |
| Contact: | Matt Rabe, 503-808-4510 |
Portland, Ore. – The U.S. Army Corps of Engineers has awarded a $9.8 million contract to ASI RCC, Inc. of Buena Vista, Colo., to open the diversion tunnel at Cougar Dam on the South Fork McKenzie River.
The diversion tunnel work is part of the Willamette Temperature Control project designed to improve river conditions for salmon and steelhead in the McKenzie River. Construction will begin in July.
Cougar Dam is located 42 miles east of Eugene, Ore.
Workers will install regulating gates inside the dam's diversion tunnel and will remove the concrete plug that closed up the tunnel after the dam was completed in 1963. Work on the tunnel is scheduled to be completed by January 2002.
Opening the tunnel will allow the Corps to lower the reservoir below the normal winter operating level during construction of a temperature control feature on the existing water control tower.
The reservoir will be lowered each summer for up to five years beginning in April 2002 while workers complete the temperature control structure.
Construction of the new temperature control feature will require the Corps to lower Cougar Reservoir to near-stream level from April to October for up to five years beginning in 2002. During this five-year period, the Corps will continue to operate the project to manage flows and minimize flood damages.
To benefit salmon and resident fish in the McKenzie River, the Corps plans to add water temperature control capabilities at Cougar and Blue River dams. Construction of the new, multiple-level intake tower, attached to the face of the existing tower, will let the Corps draw water from differing depths in the lake to adjust water temperatures of releases below the dam.
Under current conditions, unnaturally cold water is released in early to mid-summer, discouraging adult salmon from migrating into the South Fork McKenzie River. By late summer, unnaturally warm water is released, causing salmon eggs deposited in nests below the dam during the fall to hatch prematurely at a time when little food is available for them.
In 1995, the Corps released a final Environmental Impact Statement for construction of the temperature control project. In 1998, however, the Corps modified its design for construction.
The 1998 design changes include a larger residual – or temporary – pool, an unscreened opening for the diversion tunnel and placement of two cofferdams to manage water flows during construction. A portion of one of the cofferdams will be permanent to provide additional sediment control after construction. With the cofferdam in place, sediment will build up at the base of the cofferdam instead of at the base of and inside the intake structure.
As described previously in the 1995 EIS, beginning in 2002 recreation will be impacted because the reservoir's three boat ramps will not be useable. The Corps does not expect there to be any impacts to recreation downstream of the dam.
The aquatic species that may be most affected during the tower construction is bull trout, recently listed as a threatened species under the Endangered Species Act. To minimize the impacts during construction, the Corps plans to maintain a residual pool above the dam and to collect adult bull trout below the dam and transport them to release sites above the reservoir in the South Fork McKenzie River. The transported bull trout will reproduce above the reservoir assuring persistence of the population there. The Corps is working with the U.S. Fish and Wildlife Service and with Oregon Department of Fish and Wildlife to develop and implement this plan.
Following construction of the temperature control feature, bull trout also will benefit from the Corps' new ability to release water that improves temperatures below the dam.
Upon completion of the intake tower at Cougar Dam, the Corps plans to begin similar work at its Blue River Dam. The work at Cougar Dam, on the South Fork McKenzie River, and at Blue River Dam, on the Blue River, constitutes the Willamette Temperature Control Project.