Big Tujunga Dam
Encyclopedia
Big Tujunga Dam is a concrete arch dam in Los Angeles County, California
, spanning Big Tujunga Creek
northeast of Sunland. Completed in 1931 by the Los Angeles Department of Water and Power
, it serves mainly for flood control. The dam was originally planned as one of several similar flood-control dams inside Big Tujunga Canyon and was thus referred to as Big Tujunga Dam No. 1 until the large Hansen Dam
was completed in 1940, eliminating the need for the other components of the original project.
Its reservoir
is called Big Tujunga Reservoir, and has a capacity of 5960 acre feet. Although it is located inside the Angeles National Forest
, public access to the lake is forbidden. The water is kept at a low level except during the rainy season. Because of the small storage capacity of the reservoir, it has filled completely with sediment on several occasions, including 1969 and 2011; as a result frequent dredging is required to keep the dam operational.
runs nearby) and the reservoir's level was temporarily restricted to about 25% of capacity. Approximately 75000 cu yd (57,341.6 m³) of concrete was added to the dam, transforming it from a thin-arch to a thick-arch design. A new spillway
was built and the original one was expanded, increasing the release capacity from 23000 cuft/s to more than 90000 cuft/s. The seismic retrofit project was completed in July 2011 at a cost of $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...
, spanning Big Tujunga Creek
Big Tujunga Creek
Big Tujunga Creek is a major stream in Los Angeles County in the U.S. state of California. From its headwaters high in the San Gabriel Mountains, it flows generally southwest for , joining Little Tujunga Creek to form the Tujunga Wash near Pacoima...
northeast of Sunland. Completed in 1931 by the Los Angeles Department of Water and Power
Los Angeles Department of Water and Power
The Los Angeles Department of Water and Power is the largest municipal utility in the United States, serving over four million residents. It was founded in 1902 to supply water and electricity to residents and businesses in Los Angeles and surrounding communities...
, it serves mainly for flood control. The dam was originally planned as one of several similar flood-control dams inside Big Tujunga Canyon and was thus referred to as Big Tujunga Dam No. 1 until the large Hansen Dam
Hansen Dam
Hansen Dam is a dam in Lake View Terrace, Los Angeles, California. It was built in 1940 by the U.S. Army Corps of Engineers, Los Angeles District...
was completed in 1940, eliminating the need for the other components of the original project.
Its reservoir
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...
is called Big Tujunga Reservoir, and has a capacity of 5960 acre feet. Although it is located inside the Angeles National Forest
Angeles National Forest
The Angeles National Forest of the U.S. National Forest Service is located in the San Gabriel Mountains of Los Angeles County, southern California. It was established on July 1, 1908, incorporating the first San Bernardino National Forest and parts of the former Santa Barbara and San Gabriel...
, public access to the lake is forbidden. The water is kept at a low level except during the rainy season. Because of the small storage capacity of the reservoir, it has filled completely with sediment on several occasions, including 1969 and 2011; as a result frequent dredging is required to keep the dam operational.
Seismic retrofit project
In 1976, the dam was recognized as in danger of failure from earthquakes (the San Andreas FaultSan Andreas Fault
The San Andreas Fault is a continental strike-slip fault that runs a length of roughly through California in the United States. The fault's motion is right-lateral strike-slip...
runs nearby) and the reservoir's level was temporarily restricted to about 25% of capacity. Approximately 75000 cu yd (57,341.6 m³) of concrete was added to the dam, transforming it from a thin-arch to a thick-arch design. A new spillway
Spillway
A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...
was built and the original one was expanded, increasing the release capacity from 23000 cuft/s to more than 90000 cuft/s. The seismic retrofit project was completed in July 2011 at a cost of $100 million.