Tallest Concrete Arch Dam in the World

Pacoima Dam is a concrete constant angle arch dam on Pacoima Creek in the San Gabriel Mountains along Pacoima Creek. Pacoima Creek is a major tributary of Tujunga Creek, which is one of the main tributaries of the Los Angeles River.

The dam is 365 feet (113 m) tall, 640 feet long at its crest, is 100 feet thick at its base, and creates a reservoir with a capacity of 3,777 acre feet (4,659,000 m³). Pacoima Dam was built by the Los Angeles County Flood Control District which became part of the Department of Public . When it was completed in 1928, it was the tallest arch dam in the world. It is also known as Reagan Dam.

Pacoima dam withstood very strong ground shaking in both the 1971 and 1994 earthquakes. The United States Geological Survey (USGS) began monitoring the dam using continuous GPS in 1995 following the Northridge earthquake. Pacoima Dam plays a crucial role in keeping mountain runoff from flooding the Valley floor and in helping to recharge the ground-water supply.