“Tallest arch dam in the US” is quite the boast isn’t it? Here at Pacoima Dam, we’re standing before an engineering marvel. Pacoima Dam is a concrete arch dam. It spans Pacoima Creek in the San Gabriel Mountains. This is in Los Angeles County, California.
The Pacoima Dam creates Pacoima Reservoir. The reservoir has a capacity of 3,777 acre⋅ft. That’s 4,659,000 m3 of water.
The Los Angeles County Flood Control District built the dam. It later became part of the Department of Public Works. Construction finished in 1928. At that time, the Pacoima Dam was the tallest arch dam in the U.S. It stood at 371 feet high. That is 113 meters.
Pacoima Dam is located about 1 mile northeast of Sylmar. It sits above the San Fernando Valley. The district uses it as a flood control structure. They restrain flows of stormwater released from the dam. This compensates for hydraulic deficiencies downstream.
During Pacoima Dam’s construction, Roy W. Carlson was hired. He was the concrete and soil testing engineer. Carlson developed the world’s first strain meter. It could be embedded in concrete. He also created an adiabatic calorimeter. Plus, he invented electrical-resistance thermometers. These tools helped him understand concrete temperatures during curing. He aimed to avoid cracking caused by stress.
The Pacoima Dam faced very strong ground movement. This happened during the 1971 San Fernando and 1994 Northridge earthquakes. There were concerns about the dam’s stability. Specifically, how it would respond to future earthquakes. So, the County of Los Angeles and the USGS started monitoring the dam. They used continuous GPS.
In 1887, Jouette Allen purchased 1000 acres. He named the town Pacoima. The name Pacoima is from the Tataviam tribe’s “Pacoinga Village”. It means “the entrance”.
Fires have impacted Pacoima’s watershed. The Marek, Sayre, Station and Sand fires all took their toll. Storm events after these fires increased sediment in the reservoir. The Los Angeles County Flood Control District is working to remove sediment. This will restore flood control and water conservation capacity. They also want to create safe access to the reservoir. Plus, they want to increase the dam’s operational reliability and safety.
Standing here, you can appreciate the Pacoima Dam’s crucial role. It protects communities from floods. It conserves water. It also stands as a testament to engineering innovation. The Pacoima Dam’s story is one of resilience. It is a story of adaptation, in the face of natural challenges.