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CHELAN HYDROELECTRIC PROJECT QUICK FACTS:
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RESERVOIR OPERATIONS || CHELAN RIVER GORGE || WATER QUALITY || PROJECT OPERATIONS || HISTORY || POWER SALES CONTRACT || PROJECT LICENSE || THE DAM || THE POWER TUNNEL || THE POWERHOUSE || TURBINES || VALVE REPLACEMENT PROJECT || GENERATORS || SWITCHYARD || THE RESERVOIR || SNOW SURVEY || REFILL OF LAKE CHELAN || DRAWDOWN || FLOOD CONTROL| The Lake
Chelan Hydroelectric Project is located approximately 32 miles north of the city of
Wenatchee in Chelan County, near the geographic center of Washington state. The dam is
located at the lower, or southeasterly end of 55-mile-long Lake Chelan, adjacent to the
city of Chelan. The Powerhouse is located near the community of Chelan Falls. Lake Chelan is a natural body of water that developed within a broad glacial trough. The 32,000 acre lake averages one mile in width, and has depths of over 1,500 feet. It's bordered by more than 2 million acres of National Forest Lands, more than half of which are designated wilderness. |
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Power generation for the Lake Chelan Hydro Project during 1997 totaled 451 million kilowatt hours -- a 13% increase from the previous year. The 10-year average generation for the Project is 370 million kilowatt hours.
RESERVOIR
OPERATIONS
Water runoff for the Lake Chelan drainage system during 1997 was 1,530,000 acre feet, or
140% of the 55-year average of 1,040,000 acre feet. About 74% of the reservoir's available
storage was drafted for power production during the year. The surface elevation of the
Lake Chelan Project reservoir was 1,098.8 feet above sea level on January 1, 1997. The
reservoir was drawn down to its lowest elevation of the year on March 18 when it reached
1,084.65 feet above sea level --5.65 feet above the 1,079-foot minimum elevation
authorized by the Project license. The reservoir was refilled with runoff from the
accumulated snowpack when it reached elevation 1098 feet on June 29, one day in advance of
the license requirement. The reservoir reached a maximum elevation of 1,100 feet on July
31. Because of heavy inflows caused by the melting of an above-average snowpack, it became
necessary to spill water at the Lake Chelan Dam down the Chelan River Gorge to maintain
the reservoir elevation within the level specified by the Project license. The spills
totalled 555,000 acre feet of water, or the equivalent of 152.8 million kilowatt hours of
power.
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CHELAN RIVER GORGE
Lake Chelan flows into the Chelan River
at the City of Chelan. The Chelan River forms a confluence at the Columbia River about 1.5
miles southeast of the City of Chelan. The level of the lake and the flow through the
Chelan River drainage were altered with the construction of the hydroelectric project in
the river near Chelan in 1928. During high runoff periods, the Chelan Dam may be utilized
to regulate the lake level as it approaches the maximum elevation by flowing water down
the Chelan River Gorge, past the powerhouse and into the Columbia River. (view the Chelan River Gorge)
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WATER QUALITY
The implementation of a comprehensive plan for preserving the water quality of the Lake
Chelan Hydro Project reservoir continued during 1997. The plan was developed cooperatively
by the District and four other local governmental entities. It's designed to serve as a
blueprint for guiding future development and regulation of the Lake Chelan Basin, as well
as provide a means for finding remedies for existing causes of water pollution.
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PROJECT
OPERATIONS
The Lake Chelan Hydro Project's 2.2-mile-long penstock was unwatered and inspected during
the year. The underground concrete and steel tunnel delivers water from the dam at the
southeasterly end of Lake Chelan to the powerhouse at Chelan Falls, a vertical drop of
nearly 400 feet. The penstock must undergo a federally required inspection every five
years. The 1996 inspection found the structure to be in excellent condition.
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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.
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POWER
SALES CONTRACT
The PUD purchased the Lake Chelan Hydro Project from Washington Water Power (WWP) in July
1955, with the proceeds of a $21 million bond issue. All of the power produced by the
Project was sold to WWP, under the terms of a 40-year contract. The agreement allowed the
District to withdraw from WWP all of the power required to meet the electrical needs of
the local area, up to 168,000 kilowatt hours annually. That contract ended on June 22,
1995. Today, all the power generated by the Project is available for Chelan County homes
and businesses.
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PROJECT
LICENSE
The Project License sets forth the terms of operation and responsibility. The original
license was granted for the present Lake Chelan Hydroelectric Project in May 1926 under
the Federal Power Act of 1920. On May 12, 1981, the Federal Energy Regulatory Commission
granted the District a new 30-year license for the project, retroactive to 1974 when the
original 50-year license expired. That license expires in 2004. (click
here to view current license order) Chelan County PUD intends to seek a new federal
license to operate the Lake Chelan Hydro Project and has begun preparation for the process
referred to as relicensing.
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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 intake to the penstock
or power tunnel is located on the west abutment.
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THE POWER
TUNNEL
Water to power the turbine generators is delivered through an underground tunnel
connecting the dam and the powerhouse. This steel and concrete tunnel is approximately 2.2
miles in length and has a total vertical drop of nearly 400 feet. The only visible portion
of the tunnel is a 130-foot-high surge tank that's designed to absorb the hydraulic
momentum of the falling water, in the event that flow through the powerhouse needs to be
stopped.
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THE
POWERHOUSE
The powerhouse is located along the Columbia River, near the community of Chelan Falls. It
is 140 feet long, 100 feet wide and 124 feet high.The structure houses two generating
units, which are rated at 24,000 kilowatts each, with a peaking capability of 58,000
kilowatts. Besides the two generating units, the powerhouse contains a Control Room, shop
facilities, switching equipment, a 117-ton bridge crane and communications equipment. The
plant can be operated from the Control Room or by remote control, via microwave link, from
the Central Dispatch Center located in the Wenatchee Headquarters Building.
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TURBINES
Water traveling down the power tunnel is directed against two Francis-type hydraulic
turbines rated at 34,000 horsepower each. The turbines rotate at 300 revolutions per
minute. The original turbines were replaced in 1985 and 1986.The turbines are connected to
the generators by steel shafts approximately 30 feet long and 21 inches in diameter.
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VALVE
REPLACMEMENT PROJECT
Installation of new turbine inlet
valves at the powerhouse is scheduled to begin in late spring 1998. The project will
require a three-month shutdown of the powerhouse, which will include removing water from
the underground tunnel and penstock. Construction of a pumping plant began in the
powerhouse tailrace in 1997 to maintain deliveries of irrigation water that are normally
drawn from the penstock during an outage.
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GENERATORS
The two General Electric generators are rated at 24,000 kilowatts each. They provide a
combined peaking capability of 58,000 kilowatts. These machines produce 3-phase 60-cycle
power at 11,000 volts. The original generators were rewound in 1951 and 1952. 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.
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SWITCHYARD
Electrical energy is transmitted from the powerhouse to an adjacent switchyard where six
main power transformers step up the generated power from 11,000 volts to 115,000 volts.
Four transmission lines are connected to the switchyard. Local service is provided by the
Wapato and Chelan/Manson lines. The Stratford Line interconnects with Washington Water
Power's service area. The station is also connected with the Rocky Reach Project, located
on the Columbia River, to ensure reliability of service.
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THE RESERVOIR
Under terms of the existing license, the project reservoir is operated between a maximum
water surface elevation of 1,100 feet above sea level and a minimum water surface
elevation of 1,079 feet. This ensures optimal use of the reservoir for power generation at
the Project; fish and wildlife conservation; recreation; municipal and domestic water
supplies; flood control; and power generation downstream. Under terms of the existing
license, the PUD must also make every reasonable effort to maintain the reservoir at or
above elevation 1,098 from June 30 through September 30 each year.The average drawdown of
the lake during the past 50 years has been to elevation 1,084.
Inflow in excess of the reservoir storage capacity and hydraulic capacity of the
generating plant is discharged through the diversion and control dam spillway.The
reservoir has 677,400 acre feet of usable storage above the 1,079-foot level. Of that
total, 65,000 acre feet is set aside for irrigation and domestic water uses and the rest
is used for power generation.
Annual Cycle -
Reservoir Elevation
The annual drawdown of the lake begins in early October, when average inflows into the
reservoir decline as the result of cooler weather. From October through April, the volume
of water flowing down the penstock to the powerhouse typically exceeds inflows into the
reservoir. From May through June, warmer weather melts the accumulated winter snowpack.
During this period, average inflows exceed outflow capabilities causing the reservoir to
refill. Weather conditions influence the rate of snowmelt and volume of runoff. The
District uses snowpack surveys and telemetry readings of the Chelan Basin drainage system
to continually adjust forecasts for the runoff. These forecasts provide for a timely and
complete refill of the reservoir. During high runoff periods, the Chelan Dam may be
utilized to regulate the lake level as it approaches the maximum elevation by flowing
water down the Chelan River Gorge, past the powerhouse and into the
Columbia River.
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SNOW SURVEY
The District conducts five annual snowpack surveys of the Chelan Basin drainage system.
This data, along with information collected from four snowpack monitoring telemetry sites,
is the basis for runoff forecasts that are an important factor in maximizing power
generation and ensuring the timely refill of the reservoir. The forecasts are made
available to the general public and to local news media. Over the years, these forecasts
have proven to be within 5 percent of the actual inflow.
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REFILL
OF LAKE CHELAN
From May through June, warmer weather melts the accumulated winter snowpack. During this
period, average inflows exceed outflow capabilities causing the reservoir to refill.
Weather conditions influence the rate of snowmelt and volume of runoff. Operation of the
project spillgates serves to regulate the lake level as it approaches maximum elevation. (see annual cycle - reservoir elevation above)
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DRAWDOWN
The reservoir is drawn down during the winter months as a result of Project power
generation. With both generators operating at maximum capability, the lake is drafted at a
rate of 2,200 cubic feet per second. (see annual cycle - reservoir
elevation above)
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FLOOD CONTROL
The District's operation of the reservoir also serves to protect shoreline property from
flooding. In 1894, floodwaters pushed the lake level 11 feet above the old (pre-project)
high water mark. The spillway section of the dam was sized and constructed to avoid a
reoccurrence of such flooding. Protection from flooding is also a consideration in
refilling the lake.
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Surrounding mountain peaks tower as high as
9,000 feet above its 55-mile length.The lake serves as a waterway approach to the
Wenatchee National Forest above Twenty Five Mile Creek and the Lake Chelan National
Recreation Area of Stehekin.