LAKE CHELAN DAM
History
The Chelan River has a long, colorful history of dam development for navigation, water supply, and power generation. The first dam built to raise the level of Lake Chelan was completed in 1892. It was constructed to provide water for south Chelan real estate and navigation to the city of Chelan. It washed out during June of that year, only to be replaced by another structure built by the newly formed Chelan Water Power Company in 1893. This much larger and stronger dam was designed to raise the lake level enough to allow steamships to land at Chelan. However, even this structure lasted only a year before falling victim to a massive flood in June 1894. In early 1899, M.M. Kingman purchased the Chelan Water Power Company and proceeded to build another dam, this time for power generation. The "turning on of lights" was celebrated in Chelan in May 1903. The Chelan Water Power Company was purchased by the Chelan Electric Company in 1906. That firm was then purchased by Spokane-based Washington Water Power Company in 1925. A year later, Washington Water Power received a 50-year federal license to construct the existing dam and powerhouse. The first generating unit was placed in commercial operation in September 1927, followed by the second unit 11 months later.
The Dam
The dam is a steel-reinforced concrete gravity structure. It is approximately 40 feet high and 490 feet long. It contains eight spillway bays. When the spillway gates are open, water is discharged down the normally dry Chelan River channel.
The Power Tunnel
Water to power the turbine generators is delivered through an underground penstock connecting the dam and the powerhouse. It delivers water from the dam at the southeasterly end of Lake Chelan to the powerhouse at Chelan Falls, a vertical drop of nearly 350 feet. This steel and concrete tunnel is approximately 2.2 miles in length. The only visible portion of the tunnel is a 125-foot-high surge tank constructed on the hill above the plant to absorb hydraulic momentum of the water in case of load rejection. The penstock must undergo a federally required inspection every five years.
The Powerhouse
The powerhouse is located at Chelan Falls. It is 140 feet long, 100 feet wide and 124 feet high. Besides the two generating units, the powerhouse contains a control room, shop facilities, switching equipment, crane and communications equipment.
Turbines
Water traveling down the power tunnel is directed against two turbines rated at 42,662 horsepower each. The turbines, which are connected to the generators by steel shafts, rotate at 300 revolutions per minute. The original turbines were replaced in 1985 and 1986, and those were replaced in 2009 and 2010.
Generators
The generators are rated at 29,600 kilowatts each. Together, they provide a normal operating output of 62 megawatts. The original generators were rewound in 1951 and 1952. New generators and other equipment were installed in 2009 and 2010, increasing output by nearly 15 percent. After passing around and through the turbine blades, water is discharged into the tailrace located on the east side of the powerhouse where it flows into the Columbia River.
From the Chelan PUD