Water Facts - Folsom Dam, Lake, and Powerplant
Folsom Dam
- Measures 340 feet high and 1,400 feet long
- A concrete gravity type dam flanked by long earthfill wing dams, plus an earthfill auxiliary dam at Mormon Island and 8 earthfill dikes to close the reservoir rim
- Has enough concrete to build a highway (8 inches thick by 16 feet wide) from the Oregon border to Bakersfield, California, or a sidewalk (4 inches thick by 3 feet wide) from San Francisco to New York City
- Weighs 2,343,000 tons, but it is 40 percent hollow inside
- Part of the Central Valley Project
- Water Pressure on Folsom Dam
- Measures 14,976 pounds per square foot at the base
- Equivalent to one person standing on a foot-square tile, bearing 100 people on their shoulders
- Services Provided by Folsom Dam
- Water supplies for irrigation, domestic, municipal, industrial, and power production
- Flood protection for the Sacramento metropolitan area
- Maintenance of navigation along the lower reaches of the Sacramento River
- Water quality control for project diversions from the Sacramento-San Joaquin Delta
- Maintenance of fish runs in the American River below Nimbus Dam
- Water-related recreation and wildlife viewing opportunities
- Flood Control Provided by Folsom Dam
- During a normal year's runoff from the Sierra Nevada, 2.7 million acre-feet of water comes into Folsom Lake.
- A maximum of 40 percent to 60 percent capacity is reserved for the control of flood flows during the late fall and winter months.
- Over $4.8 billion in flood damage has been avoided.
- Major Flood Events
- December 1955 - Tropical rain storm at 10,000 feet; first usage of the dam for flood control purposes.
- December 1964 - Lower Hell Hole Dam on the Rubicon River failed upstream of Folsom Dam. An estimated $45 million in flood damage was prevented.
- February 1986 - winter storm with unprecedented intensity. Many areas received nearly half their average annual rainfall in this one week period. Auburn coffer dam fails.
- December 1997 - 65 year flood event on the American River
Folsom Powerplant
- 3 generators
- Combined capacity of 198,720 kilowatts of electrical power
- Enough power to light 2 million 100-watt light bulbs
- 10% of Sacramento's electrical needs
Folsom Dam and Powerplant Construction History
- Dam construction began on October 12, 1948.
- Powerplant construction began on April 28, 1952.
- Initial storage of water behind Folsom Dam began in the spring of 1955.
- Sufficient water storage permitted the generation of electric power starting May 20, 1955.
- Full capacity power production with all generators functioning attained on December 6, 1955.
- Powerplant construction completed on March 14, 1956.
- Dam construction completed on May 9, 1956.
Folsom Lake
- Impounds the runoff from 1,875 square miles (American River watershed)
- Total storage capacity of 975,000 acre-feet 75 miles of shoreline
- Enough water to cover the state of Rhode Island with 1.5 feet of water
- Recreation opportunities managed by California State Parks
