Feather River “Stairway of Power”
In the early 1880's Civil Engineer Julius M. Howells first noted
the possibility of a great storage reservoir at Big Meadows, now the
site of Lake Almanor. By a later survey Howells found that the river
in its plunging course dropped 4,350 feet in the first 74 miles.
Today Pacific Gas and Electric Company operates in the famous scenic
Feather River Canyon a descending "stairway" of powerhouses which
utilize the water over and over for power before it flows on
undiminished to other uses.
From the construction of Big Bend Powerhouse in 1908 to the completion of the most recent plants, the North Fork of the Feather has served as a proving ground for advanced hydroelectric engineering principles. The building of Big Bend Powerhouse by Great Western Power Company, which in 1930 became a part of PG&E, made news in engineering journals throughout the world. Among world "firsts" in electrical advancements at Big Bend were the largest waterwheels, transformers and penstocks that had then been built.
PG&E's service area includes all or a portion of 47 of California's 58 counties and encompasses nearly 94,000 square miles of northern and central California. The reservoirs and powerhouses on the Feather River are broken down into what PG&E calls projects.
The Hamilton Branch Project consists of the Mountain Meadows Reservoir (also known as Walker Lake), a diversion and canal system with pumping stations; and the 4.7 megawatt Hamilton Branch powerhouse on the shore of Lake Almanor.
The Upper North Fork Feather River Project consists of three dams and reservoirs, five powerhouses, tunnels and penstocks connecting the reservoirs to the powerhouses, 230 kilovolt and 115 kilovolt transmission facilities, and various roads, recreation facilities, and administrative facilities. Project reservoirs include Lake Almanor, Butt Valley reservoir, and Belden Forebay. Powerhouses include Butt Valley Powerhouse, Caribou No. 1 and Caribou No. 2 Powerhouses, Oak Flat Powerhouse, and the Belden Powerhouse.
The Bucks Creek Project is operated in cooperation with the City of Santa Clara and is located 10 miles west of Quincy, California. In 1925, the Bucks Creek Project was undertaken by the Feather River Power Company. Part of the project, Bucks Dam, was completed in 1929. Title passed to the Great Western Power Company that same year, and later to Pacific Gas and Electric Company. About half of the shoreline is now owned by Pacific Gas and Electric and the other half is under the management of the Forest Service. The Grizzly Powerhouse, owned by the City of Santa Clara, was added to this project in the early 1990’s.
The Poe Project consists of the Poe Diversion Dam, the Poe Reservoir, a concrete intake structure located on the shore of Poe Reservoir, a pressure tunnel about 19 feet in diameter with a total length of about 33,000 feet, a differential surge chamber located near the downstream end of the tunnel, a steel underground penstock about 1,000 feet in length and about 14 feet in diameter, a reinforced concrete powerhouse, with two vertical shaft Francis-type turbines, the Big Bend Dam, and the Poe Afterbay Reservoir.
The Rock Creek/Cresta Hydroelectric Project consists of the Rock Creek and Cresta developments, each of which has a dam, reservoir, tunnel, powerhouse, and associated transmission facilities.
The Rock Creek development includes: the Rock Creek Reservoir, the Rock Creek Dam, an intake structure within the reservoir, about 100 feet upstream of the dam near the western abutment, a 34,110-foot-long tunnel with two cross-sections, a 25-foot-diameter horseshoe and a 19-foot-diameter circular section, an underground surge chamber, two penstocks, 906 and 938 feet long with diameters varying from 12 feet to 9.75 feet, a powerhouse containing two Francis-type turbine-generator units, and a switchyard, adjacent to the powerhouse, containing two transformer units to step up generator voltage from 13.8 kilovolts to 230 kilovolts.
The Cresta development includes: the Cresta Reservoir, the Cresta Dam, an intake structure within the reservoir, about 100 feet upstream of the dam near the eastern abutment, a 21,080-foot-long tunnel with two cross-sections, a 26-foot-diameter horseshoe and a 19-foot-diameter circular section, an underground surge chamber, two 12-foot-diameter penstocks, 800 and 775 feet long, a powerhouse containing two Francis-type turbine-generator units, and a switchyard, adjacent to the powerhouse, containing two transformer units to step up generator voltage from 11.5 kilovolts to 230 kilovolts.
The North Fork Feather River powerhouses are operated in a load following mode (market dispatch) and the entire system, except for Hamilton Branch, Oak Flat and Caribou No. 1 powerhouses, is controlled by direct digital dispatch from PG&E's power control offices in San Francisco. When demand is high, the projects are operated at near peak capacity and the reservoirs provide water. When demand is low, the powerhouses may be shut down while the reservoirs refill. In addition, a large percentage of the available water is passed through Rock Creek and Cresta powerhouses during partial peak and off-peak hours at flows that provide efficient generation. In wet months, the powerhouses are operated at full capacity to make maximum use of available water. Under adverse (low flow) water conditions, the powerhouses are operated in peaking mode, drawing from water stored in the North Fork Feather River reservoirs (mainly Lake Almanor).
Just below the confluence of the North Fork Feather River, the West Branch Feather River, the Middle Fork Feather River, and the South Fork Feather River is the California Department of Water Resources' massive Lake Oroville Project. Water from Oroville Dam is released into the Feather River, which is a left bank tributary of the Sacramento River that flows into the Pacific Ocean at San Francisco Bay.
The primary storage reservoir on the North Fork Feather River is Lake Almanor. Water released from Belden reservoir and powerhouse, along with the natural flow of the East Branch North Fork Feather River and small tributaries, flows into the Rock Creek reservoir where it is diverted through a tunnel to two parallel penstocks that serve the Rock Creek powerhouse. Water released from the Bucks Creek powerhouse enters the North Fork Feather River about 1 mile above the Rock Creek powerhouse.
The combined flow from Rock Creek and Bucks Creek facilities, along with the flow from several small tributaries along the North Fork Feather River, enter the Cresta reservoir. Water is diverted through a tunnel to two parallel penstocks that serve the Cresta powerhouse. Water released from this powerhouse enters the Poe reservoir.
Lake Almanor Reservoir and Dam
Construction of Almanor Dam was started by the Great Western
Power Company in 1910 in order to provide water storage for Big Bend
Powerhouse, located upstream from Oroville, and irrigation in the
central valley. While Big Bend Powerhouse was later flooded by Lake
Oroville, Lake Almanor now provides water storage for six Pacific
Gas and Electric Co. hydro-electric plants, Butt Valley Powerhouse,
Caribou #1 and #2 Powerhouses, Oak Flat, Belden Powerhouse, Rock
Creek Powerhouse, Cresta Powerhouse, and Poe Powerhouse which are
located downstream on the North Fork Feather River as well as for
Originally conceived as a masonry dam, Almanor Dam was constructed as an earth dam when poor foundation conditions were encountered. The name "Almanor" was created by combining the names of the three daughters of Great Western Power Company's Vice-President Guy C. Earl - ALice, MArtha, and ElaNOR. The Great Western Power Company also formed a subsidiary know as the Western Canal Company to distribute irrigation water to farmers west of Oroville. The Western Canal Water District continues to hold water rights that require water be released from Lake Almanor (and other smaller PG&E reservoirs located in the Feather River watershed) during the irrigation season (March 1 through October 31).
Water is normally released through the Prattville Tunnel for power generation at Butt Valley Powerhouse, Caribou Powerhouse, and Belden Powerhouse and other plants downstream as well as irrigation. The tunnel outlet is located on the west shore of Lake Almanor at Prattville where two outlet towers can be seen. The northward tower is the entrance for the Prattville Tunnel. The southward tunnel, used before Butt Valley Powerhouse was constructed, is now plugged. During wet years water can also be released through the outlet tower located just upstream of the dam. This has only happened once.
Completed in 1914 it was raised in 1927 and again in 1962. The maximum storage elevation is 4494 feet and volume of the lake at maximum storage is 1,142,964 acre-feet with a maximum reservoir surface area of 28,257 acres. Maximum dam height is 130 feet with a crest length of 1,250 feet. The spillway elevation is 4,500 feet.
Because the spillway is six feet above the maximum storage operating level, the spillway is never used. Instead, when necessary to not exceed the maximum storage level, water is released through the outlet tower located just upstream of the dam. Google Earth coordinates are 40° 10' 23.36" N 121° 05' 26.33" W.
Mountain Meadows Reservoir and Indian Ole Dam (Walker Lake)
Originally constructed in 1924 and later reconstructed in 1962 on Hamilton Branch Creek, Indian Ole dam and Mountain Meadows reservoir provides storage for Hamilton Branch Powerhouse, which is located on the east shoreline of Lake Almanor. At a maximum storage elevation of 5,040.6 feet the maximum storage is 23,900 acre-feet with a surface area of 5,700 acres. Maximum dam height is 26 feet with a crest length of 264 feet. This reservoir is also known locally as Walker Lake. The reservoir is very shallow and storage can drop to 1700 acre-feet in a dry year. Releases from the reservoir are diverted from the Hamilton Branch at the Hamilton Branch Diversion Dam approximately 2 miles downstream from Indian Ole Dam. The 200-cfs capacity diversion canal is a little over three miles long and carries water to the Hamilton Branch Powerhouse. Two other diversion dams located on Clear Creek and the Hamilton Branch at Red Bridge provide additional flow to the canal. Google Earth coordinates are 40° 17' 00.98" N 121° 01' 29.61" W.
Hamilton Branch Powerhouse
One of the early powerhouses it was commissioned in 1921. Water is supplied from the Mountain Meadows Reservoir from which it can produce 4,800 kilowatts (4.8 megawatts) of electricity. Google Earth coordinates are 40° 16' 07.39" N 121° 05' 22.06" W.
Butt Valley Powerhouse
Completed in 1958 water for the turbines is fed through a 2.2 mile long tunnel and a mile long penstock from Lake Almanor with a total water drop of 368 feet. Power production is 41,000 kilowatts (41 megawatts). It was built with an outdoor generator for economy in construction. Google Earth coordinates are 40° 10' 32.61" N 121° 11' 26.37" W.
Butt Valley Reservoir and Dam
This reservoir was constructed on Butt Creek by the Great Western Power Company starting in 1919 to provide water storage for the Caribou Powerhouse being completed in 1924. At a maximum storage elevation of 4142.2 feet the volume of the lake at maximum storage is 49,891 acre-feet with a maximum reservoir surface area of 1,600 acres. Maximum dam height is 84 feet with a crest length of 1,370 feet. The spillway elevation is 4,132.1 feet. A dinky engine, used in the original construction of the dam was discovered in 1997 when the reservoir was drained for repair work. It had been submerged for about 70 years. The restored engine is now on display on Highway 36 on the west end of Chester. Google Earth coordinates are 40° 06' 54.12" N 121° 08' 41.16" W.
Caribou Powerhouse 1
Completed in 1921 it has three generators capable of producing up to 75,000 kilowatts (75 megawatts) of electricity, with provision made for possible future expansion. A 1.8-mile tunnel and three 2,222-foot penstocks with a water drop of 1,149 feet supply the generators. From the Caribou Powerhouses water flows into the Caribou Afterbay/Belden Forebay Dam, this re-regulates the flow before it joins the main river at Belden. Google Earth coordinates are 40° 05' 07.67" N 121° 08' 53.75" W.
Caribou Powerhouse 2
Located next to powerhouse 1 this partially underground
generating facility was commissioned in 1958 and can produce 120,000
kilowatts (120 megawatts) of electricity. Water is supplied through
a 1.6-mile tunnel and a 2,322-foot penstock. Water drop is 1,150
feet. Illustrating the new cost saving design with generators
outdoors instead of in a large building the advanced high efficiency
impulse turbines are driven by six jets ranged around the water
Each powerhouse is operated independently from the other. Normally the newer and more efficient Caribou #2 is operated in favor of the older Caribou #1. When power demands are high, both powerhouses are operated together. Google Earth coordinates are 40° 05' 09.48" N 121° 08' 57.78" W.
Caribou Afterbay/Belden Forebay Reservoir and Dam, Oak Flat Powerhouse
Constructed by PG&E in 1958, the dam diverts water released from
Butt Valley reservoir to Belden Powerhouse. 165 feet high and 548
feet long at its crest this reservoir serves a dual purpose as an
afterbay for Caribou and a forebay for the Belden Powerhouse. At a
maximum storage elevation of 2,985.7 feet the volume of lake at
maximum storage is 2,477 acre-feet with a maximum reservoir surface
area of 42 acres. With a maximum dam height of 84 feet and a crest
length of 400 feet the spillway elevation is 2,960.5 feet at the
bottom of the radial gate.
Oak Flat Powerhouse was constructed in 1985 and can generate 1,300 kilowatts (1.3 megawatts) of power from the fish water released from the Belden Dam. Google Earth coordinates are 40° 04' 33.53" N 121° 09' 39.15" W.
|Beldon Powerhouse. Frank Brehm.|
Commissioned in 1969 this powerhouse can produce 125,000 kilowatts (125 megawatts) of electricity. Water is delivered through a 6.3-mile long tunnel and a 1,292-foot penstock. The water drop is 770 feet. Google Earth coordinates are 40° 00' 26.82" N 121° 14' 57.74" W.
|Rock Creek Dam. Frank Brehm.|
Rock Creek Reservoir and Dam
Two miles below Belden it was completed in 1950 and impounds water and diverts it into a tunnel 25 feet in diameter and 6.5 miles long which was drilled through solid granite. The dam, 126 feet high and 567 feet long at its crest, contains 154,000 cubic feet of concrete and has two drum gates. Maximum storage elevation is 2,216.2 feet with a volume of lake at maximum storage of 4,400 acre-feet and a maximum reservoir surface area of 118 acres. Spillway elevation is 2,188.2 feet and has two 124-foot-wide bays, each controlled by a 28-foot-high by 124-foot-wide, hydraulically operated drum gate. During construction the highway was raised 100 feet; the old highway is now flooded. Google Earth coordinates are 39° 59' 13.09" N 121° 16' 59.21" W.
|Bucks Creek Powerhouse. Frank Brehm.|
Bucks Creek Powerhouse
Producing up to 65,000 kilowatts (65 megawatts) of electrical power it is located nine miles below Belden. This powerhouse was commissioned on March 30, 1928 and utilizes water tunneled from Three Lakes, Bucks Creek, Bucks Diversion and Grizzly Creek reservoirs with a capacity of 109,000 acre-feet. Its spectacular penstocks – pipes through which the water plunges downhill to spin the waterwheels – were shipped to America from Germany, passing through the Panama Canal. They are 4,786 feet long and drop the water 2,557.6 feet to the powerhouse and are among the longest in the world. Google Earth coordinates are 39° 54' 38.23" N 121° 19' 39.43" W.
|Rock Creek Powerhouse. Frank Brehm.|
Rock Creek Powerhouse
Located a mile below the Bucks Creek Powerhouse produces up to 112,000 kilowatts (112 megawatts) of power. Commissioned in 1950 its two generators utilize water diverted by the Rock Creek Dam through 6.5-mile tunnel. Its penstocks, 930 feet long and 12 feet in diameter, pass under the railroad and highway with a water drop of 535 feet. Constructing the electrical switchyard over the highway solved the difficult problem of its location in a narrow canyon. Google Earth coordinates are 39° 54' 19.03" N 121° 20' 43.62" W.
|Cresta Dam. Frank Brehm.|
Cresta Reservoir and Dam
Three miles below the Rock Creek Powerhouse it diverts water through a tunnel 26 feet in diameter and nearly four miles long. It is 114 feet high, 378 feet across its crest and contains 76,000 cubic feet of concrete. The main spillway with a crest elevation of 1,653.2 feet and two 124-foot-wide bays, each controlled by a floating 28-foot-high by 124-foot-long hydraulically operated drum gate automatically maintain the reservoirs level. There is also a 22.5-foot-wide supplementary spillway at elevation 1,666.2 feet, located to the east of the drum gates, and controlled by a 15-foot-high by 22.5-foot-wide radial gate. Cresta and the other dams always allow enough water to pass to maintain fish life and the scenic beauty of the river. At a maximum storage elevation of 1,681.2 feet and maximum storage capacity of 4,140 acre-feet its surface area is 95 acres. Google Earth coordinates are 39° 52' 33.89" N 121° 22' 24.60" W.
|Cresta Powerhouse. Frank Brehm.|
Four miles below its dam this powerhouse, built simultaneously with the Rock Creek powerhouse and their related dams and tunnels were completed in 1949. Its two generators can produce 70,000 kilowatts (70 megawatts) of electricity. Water for the generators arrives through a four-mile tunnel and two 12-foot diameter 800-foot penstocks. Water drop is 290 feet. There are also two pipes that look like smokestacks here that are surge towers, which act as safety valves when water flow through the penstocks is shut off. Google Earth coordinates are 39° 49' 33.30" N 121° 24' 34.98" W.
|Poe Dam. Frank Brehm.|
Poe Reservoir and Dam
60 feet high and 400 feet long at its crest it has four 50-foot-wide by 41-foot-high radial flood gates in concrete piers to control reservoir level. Maximum reservoir surface area is 53 acres. Google Earth coordinates are 39° 48' 34.86" N 121° 25' 57.07" W.
|Poe Powerhouse. Frank Brehm.|
Located just above Lake Oroville and producing 120,000 kilowatts (120 megawatts) of electricity the powerhouse was commissioned in 1953. By having an outdoor crane and omitting a large building to house the equipment construction costs were greatly reduced. Drawing water from Poe Reservoir through a 6.3-mile tunnel and an 890-foot long underground penstock the water drop is 477 feet. The penstock is connected to the main tunnel by a 242-foot vertical shaft. Google Earth coordinates are 39° 43' 22.40" N 121° 28' 11.20" W.
Big Bend Dam
About 300 feet long on the crest and 50 feet high above the river when built it was high enough to turn the water through the gates of the intake tower and to form a regulating reservoir to store water for the daily peak loads and enable the Big Bend powerhouse to operate at any load factor without wasting water. It has a gravity Ogee section of cyclopean concrete masonry, and is very broad at the base on account of the severe floods. It was believed at the time that the maximum flood would overtop the crest by about 23 ft. Today water flows over the top of the dam at all times. The foundation is a very hard and tough diorite rock, locally called greenstone. The bottom of the river was covered with large boulders and gravel, which had to be excavated. The lowest point of the foundation is 45 ft. below the original water level. It was originally intended that this dam would ultimately be built 90 feet higher, it never was. Google Earth coordinates are 39° 42' 47.08" N 121° 27' 58.56" W.
|Big Bend Powerhouse.|
Big Bend (Las Plumas)
This was the first plant to be built on the Feather River. When completed in 1908 70,000 kilowatts (70 megawatts) of power was transmitted 154 miles to Oakland, California at 100,000 volts, a record high voltage at the time. Water to the powerhouse was diverted through a 3-mile long tunnel and six 595-foot penstocks with a water drop of 465 feet. Timely completion of the Western Pacific Railroad greatly assisted this development, as there were no public roads in the canyon at that time. Water for the powerhouse was diverted through a 3-mile tunnel and six 595-foot penstocks with a drop of 465 feet. With the completion of Oroville Dam this project was abandoned and now sits under water. Google Earth coordinates of the approximate location of the powerhouse, which is underwater, are 39° 40’ 32.17” N 121° 29' 23.37” W.