Little Rock Dam, also known as Littlerock Dam, or officially as Little Rock-Palmdale Dam, is a concrete gravity dam on Little Rock Creek in

Los Angeles County Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the List of the most populous counties in the United States, most populous county in the United States and in the U.S. state of California, ...

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

, about south of

Palmdale Palmdale is a city in northern Los Angeles County in the U.S. state of California. The city lies in the Antelope Valley region of Southern California. The San Gabriel Mountains separate Palmdale from the Los Angeles Basin to the south. On Aug ...

. The dam and Little Rock Reservoir are owned by the Palmdale Water District and Littlerock Creek Irrigation District and are used for agricultural and municipal water supply and flood control. The dam is high from foundation to crest and spans across the canyon, forming a reservoir with a capacity of . The reservoir has a surface area of and receives water from a drainage area of on the north slope of the

San Gabriel Mountains The San Gabriel Mountains ( es, Sierra de San Gabriel) are a mountain range located in northern Los Angeles County and western San Bernardino County, California, United States. The mountain range is part of the Transverse Ranges and lies betw ...

. A formerly popular recreation spot, the dam, reservoir, and vicinity used to receive about 300,000 visitors each year, but since 2015, the facilities have been closed to the public. Designed by

John S. Eastwood John Samuel Eastwood (1857, in Minnesota – 1924, in California) was an American engineer who built the world's first reinforced concrete multiple-arch dam on bedrock foundation at Hume Lake, California, in 1908, and was one of California's ...

, a noted engineer of several dams in the western U.S., Littlerock was built in 1924 by the Palmdale Irrigation District (now Palmdale Water District) to provide a water supply for orchards in the area. With a height of and holding of water, it was the tallest multiple-arch reinforced concrete dam in the world at the time. The dam's design combined with its record height was highly controversial; the state mandated renovations in 1932, in which concrete buttresses were added to the dam face. In 1938, the dam nearly failed as a result of historic flooding, which led to the evacuation of hundreds of people in downstream towns. The dam was renovated again in 1966 to comply with increasing safety standards and regional urban development. In the 1970s, it was listed on the

National Register of Historic Places The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance or "great artistic ...

(NRHP). In 1994, the last major renovation of the dam was completed, which involved strengthening the face with

roller-compacted concrete Roller-compacted concrete (RCC) or rolled concrete (rollcrete) is a special blend of concrete that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of fly ash for Po ...

, hiding the original multiple-arch design and transforming it to resemble a conventional gravity dam. The arches are still visible on the back face of the dam when the water level in the reservoir is low. The design changes resulted in the dam being taken off the NRHP. The dam was also raised and a new

spillway A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure th ...

added, increasing the reservoir capacity to its current . The dam and reservoir are scheduled for a major renovation project in three separate phases. The first phase begins with construction of a subterranean grade control structure within Littlerock Reservoir at Rocky Point. The second phase is the removal of of accumulated sediment from within the reservoir over a seven- to twelve-year time frame. Finally, scheduled ongoing sediment removal of approximately per year to maintain design capacity. There are no plans to reopen its facilities to the public. The

California Office of Environmental Health Hazard Assessment The Office of Environmental Health Hazard Assessment, commonly referred to as OEHHA (pronounced oh-EEE-ha), is a specialized department within the cabinet-level California Environmental Protection Agency ( CalEPA) with responsibility for evaluatin ...

(OEHHA) has developed a safe eating advisory for Little Rock Reservoir based on levels of mercury or

PCBs Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act in 1979 and internationally by t ...

found in fish caught from this water body.

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* * {{LA County dams Dams in California Dams completed in 1924 Gravity dams Historic American Engineering Record in California Multiple-arch dams Roller-compacted concrete dams

See also

References

External links