Anderson Reservoir
Encyclopedia
Anderson Reservoir is a man-made lake along Coyote Creek in Santa Clara County, California
, near Morgan Hill
. Anderson Dam was built in 1950 to provide drinking water for Santa Clara county; the lake has also become a source of recreation to nearby residents. Anderson Reservoir is the largest man-made lake in Santa Clara County. It is sometimes called Anderson Lake.
, which runs from Hollister
to Milpitas
. It holds 90000 acre.ft of water when full—more than the other nine reservoirs in the county combined. In January, 2009, a preliminary routine seismic study suggested a small chance that a high-magnitude
earthquake (6.6 with the dam at the epicenter
, or 7.2 up to a mile away) could result in flooding in Morgan Hill and up to as far away as San Jose
. In response, the Santa Clara Valley Water District
(SCVWD) lowered the water level to 74% capacity and announced further analysis of the situation, which could possibly result in retrofitting the dam if necessary. Updated findings in October, 2010 indicated that the dam could fail if a magnitude 7.25 earthquake occurred within 2 kilometers of the dam, potentially releasing a wall of water 35 feet high into downtown Morgan Hill in 14 minutes, and 8 feet deep into San Jose within three hours. In response SCVWD has lowered the water to 54% full, which is 60 feet below the dam crest.
In July 2011 the Santa Clara Valley Water District issued a report stating that the seismic stability study on Anderson Dam was completed. The storage restriction that has been in place since October 2010 was adjusted, allowing 12 additional feet of storage which measures 68 percent of the dam's capacity, up from 57 percent. The water district has initiated a capital project for a seismic retrofit by the end of 2018. The operating restriction will remain in place until the project is completed.. According to the SCVWD, remediation of the problem will cost as much as $100 million.
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, near Morgan Hill
Morgan Hill, California
Morgan Hill is a city located in the southern part of Santa Clara County, California, United States. Founded on November 10, 1906, the city was named after Hiram Morgan Hill, a San Franciscan who built a country retreat home there in 1884...
. Anderson Dam was built in 1950 to provide drinking water for Santa Clara county; the lake has also become a source of recreation to nearby residents. Anderson Reservoir is the largest man-made lake in Santa Clara County. It is sometimes called Anderson Lake.
Risk of Dam Failure
Anderson Dam sits on Cochrane Road, east of Morgan Hill, and along the Calaveras FaultCalaveras Fault
The Calaveras Fault is a major branch of the San Andreas Fault located in northern California in the San Francisco Bay Area. To the east of the Hayward-Rodgers Creek fault, the Calaveras fault extends 123 km, splaying from the San Andreas fault near Hollister and terminating at Danville at its...
, which runs from Hollister
Hollister, California
Hollister is a city in and the county seat of San Benito County, California, United States. The population was 34,928 at the 2010 census. Hollister is primarily an agricultural town.-History:...
to Milpitas
Milpitas, California
Milpitas is a city in Santa Clara County, California. It is a suburb of the major city of San Jose, California. It is located with San Jose to its south and Fremont to its north, at the eastern end of State Route 237 and generally between Interstates 680 and 880 which run roughly north/south...
. It holds 90000 acre.ft of water when full—more than the other nine reservoirs in the county combined. In January, 2009, a preliminary routine seismic study suggested a small chance that a high-magnitude
Richter magnitude scale
The expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
earthquake (6.6 with the dam at the epicenter
Epicenter
The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...
, or 7.2 up to a mile away) could result in flooding in Morgan Hill and up to as far away as San Jose
San Jose, California
San Jose is the third-largest city in California, the tenth-largest in the U.S., and the county seat of Santa Clara County which is located at the southern end of San Francisco Bay...
. In response, the Santa Clara Valley Water District
Santa Clara Valley Water District
The Santa Clara Valley Water District provides stream stewardship, wholesale water supply and flood protection for Santa Clara County, California, in the southern San Francisco Bay Area. The district encompasses all of the county’s and serves the area’s 15 cities, 1.7 million residents and more...
(SCVWD) lowered the water level to 74% capacity and announced further analysis of the situation, which could possibly result in retrofitting the dam if necessary. Updated findings in October, 2010 indicated that the dam could fail if a magnitude 7.25 earthquake occurred within 2 kilometers of the dam, potentially releasing a wall of water 35 feet high into downtown Morgan Hill in 14 minutes, and 8 feet deep into San Jose within three hours. In response SCVWD has lowered the water to 54% full, which is 60 feet below the dam crest.
In July 2011 the Santa Clara Valley Water District issued a report stating that the seismic stability study on Anderson Dam was completed. The storage restriction that has been in place since October 2010 was adjusted, allowing 12 additional feet of storage which measures 68 percent of the dam's capacity, up from 57 percent. The water district has initiated a capital project for a seismic retrofit by the end of 2018. The operating restriction will remain in place until the project is completed.. According to the SCVWD, remediation of the problem will cost as much as $100 million.