Spill at Chelan Dam. 1999

Spill at Chelan Dam. 1999

The Lake Chelan Hydroelectric Project is located on the Chelan River, near the City of Chelan, in Chelan County, Washington. The project occupies 465.5 acres of federal lands administered by the U.S. Forest Service (Forest Service) and U.S. Department of the Interior, National Park Service (Park Service).

Project Name Lake Chelan
LIHI Certificate Number 30
LIHI Effective and
Expiration Dates
September 26, 2012
September 26, 2017
Owner Public Utility District No. 1 of Chelan County
State Washington
Location Located on the Chelan River, near the city of Chelan, in Chelan County, Washington.
Installed Capacity 48 MW
Average Annual Generation 380,871 MWh (1980-1999 average)
Facility Type
FERC No. 637

The Lake Chelan Project consists of (a) Lake Chelan, a 1,486-foot deep, 55-milelong natural glacial lake that was raised 21 feet by the construction of the dam to a normal maximum water surface elevation of 1,100 feet mean sea level (msl); (b) a 40-foot-high, 490-foot-long concrete gravity dam; (c) a reinforced-concrete side discharge intake structure that is integral with the dam; (d) a 14-foot-diameter, 2.2-mile-long power tunnel; (e) a 45-foot-diameter by 125-foot- high steel surge tank; (f) a 90-foot-long penstock that transitions from 14 feet in diameter to 12 feet in diameter before bifurcating to two 90-foot-long, 9-foot-diameter steel penstocks; (g) a powerhouse containing two vertical-shaft, Francis-type turbine generators with a rated capacity of 24,000 kilowatts (kW) each for a total rated capacity of 48,000 kW; and (h) a 1,700-foot-long excavated tailrace adjacent to the confluence of the Chelan River and the Columbia River that returns the project flows to the Columbia River. The average annual electric generation by the project was 380,871 megawatt-hours (MWh) for the 20-year period, 1980-1999.

The Lake Chelan Project, which can be operated locally or remotely from Chelan PUD’s Wenatchee Dispatch Center, operates at full or near full capacity almost year round. Chelan PUD operates the project to maintain reservoir elevations between 1,100 and 1,079 feet msl, with the reservoir maintained above 1,098 feet for most of the summer recreation period. The reservoir is drawn down annually for power generation and storage of spring snowmelt beginning in early October, with the lowest lake levels being reached in April. The lake is refilled through May and June, to attain an elevation of 1,098 feet on or before June 30, where it is maintained above 1,098 feet through September 30. Spills typically occur during May, June, and July, when inflows exceed the hydraulic capacity of the powerhouse units (2,300 cubic feet per second (cfs)) or when generation is curtailed. Water is spilled over the spillway into the 4.5- mile-long reach of the Chelan River that is bypassed by the project.

Under the new license, Chelan PUD would have slightly greater flexibility in managing lake levels by establishing target elevations to be achieved between May 1 and October 1, rather than a fixed elevation by a date certain. Chelan PUD proposes to manage minimum lake elevations based on snow pack conditions, lake levels, predicted precipitation and runoff conditions, and operational objectives of maintaining minimum instream flows in the Chelan River, reducing high flows (greater than 6,000 cfs) in the Chelan River, providing usable lake levels for recreation (between 1,090 and 1,098), and ensuring the project can pass the probable maximum flood without dam failure, among other objectives. The previous license did not require a minimum flow release to the bypassed reach of the Chelan River. Chelan PUD proposes a minimum flow for the entire bypassed reach, supplemented with pumping of additional water from the tailrace into the lower portion of the Chelan River (Reach 4) to improve spawning habitat for listed salmon and steelhead. The proposed minimum flow varies depending on the time of year and whether it is a dry, normal, or wet water year.

Lake Chelan is a 32,560-acre reservoir at normal maximum water surface elevation of 1,100 feet msl, with a gross storage capacity of 15.8 million acre-feet and a useable storage of 677,400 acre-feet between elevations 1,079 and 1,100. Approximately 2,000 acres of land lie within the Lake Chelan Project boundary which follows the 1,100-foot contour line from the upper end of Lake Chelan near Stehekin, Washington, to the City of Chelan then continues down both sides of the 4.5-mile-long bypassed reach of the Chelan River to the confluence of the Chelan and Columbia rivers. About 1,300 acres of the project lands are inundated and project facilities occupy the other 700 acres. The project lands are owned by the Forest Service, Park Service, several state agencies, Chelan PUD, and private property owners. Approximately 465.5 acres are inundated federal lands.

There are no primary transmission lines included in the Lake Chelan Project.  A project switchyard located 70 feet from the powerhouse connects the project power to Chelan PUD’s interconnected transmission system.

Chelan powerhouse. 1995

Chelan powerhouse. 1995

Certification History

December 27, 2012: The Lake Chelan Project has been recertified for a second five year term, effective September 26, 2012 and expiring September 26, 2017.

January 24, 2008: The Lake Chelan Hydropower Project has been certified as low impact.


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