Additions to Chief Joseph Dam Power Project

The project was planned for 27 main generating units of which 16 were initially installed and the intake structure was completed for 11 future units. The powerhouse may be extended to provide additional peaking capacity beyond the 27 units for which the project was planned. Powerhouse extension is physically and economically feasible, and is limited only by the effect of fluctuating peaking discharges on downstream use of the river for navigation, power, recreation and other purposes. The pool elevation may be raised above the present El. 946 to El. 970 by modifications to the dam, spillway and powerhouse which include installing tendons through the existing dam into the rock foundation and prestressing them. A rated net head of 163 ft will permit the 11 added units to operate satisfactorily at the existing pool El. 946 and under possible future pool elevations up to El. 970.