How about a concrete arch reaching for the sky? That’s the Big Tujunga Number 1 Dam for you. It stands tall in the Angeles National Forest.
We’re here at the Big Tujunga Number 1 Dam. This dam is more than just concrete. It’s a testament to engineering and a protector of communities.
Completed in 1931, the Big Tujunga Number 1 Dam was built by the Los Angeles County Flood Control District. The Big Tujunga Number 1 Dam cost $1.2 million. That would be about $24 million today. Initially, it was known as Big Tujunga Dam No. 1. This was because it was planned as one of several dams in the canyon. The larger Hansen Dam was completed in 1940. This eliminated the need for other dams.
The Big Tujunga Number 1 Dam has impressive dimensions. It stands 244 feet high from its foundations. From the riverbed it measures 208 feet. Its length stretches 830 feet. The base is 138 feet wide and tapers to 8 feet at the crest.
The Big Tujunga Number 1 Dam’s reservoir is called Big Tujunga Reservoir. It can hold 5960 acre-feet of water at the spillway. There is a minimum pool of 1210 acre-feet. This prevents sediment from entering the dam’s outlets. The reservoir collects runoff from an 82-square-mile watershed. Public access to the lake is not allowed. The water level is kept low for winter flood protection.
The dam’s name comes from a Tongva village. The village was called Tujunga or Tuxunga. In both the Tongva and Fernandeño languages, it means “old woman’s place”. Another village near the dam was called Muxúnga. This means “place of shooting”.
During the Los Angeles flood of 1938, the Big Tujunga Number 1 Dam played a crucial role. It stopped a massive debris flow of boulders and trees. It saved Sunland, Tujunga, and Glendale from destruction.
By 1976, concerns arose about the dam’s earthquake resistance. The San Andreas Fault is nearby. The reservoir level was reduced to about 25% of its capacity. A seismic retrofit project began in 2008. About 75,000 cubic yards of concrete were added. This transformed the dam from a thin-arch to a thick-arch design. The original spillway was expanded, increasing floodwater capacity. A new spillway was built. The capacity went from 23,000 to over 90,000 cubic feet per second. A 24-inch valve was installed to release low flows for habitat conservation. The project cost $100 million. It was completed in July 2011.
Even with the Hansen Dam downstream, the Big Tujunga Number 1 Dam remains vital. It protects about 4600 residents in the Big Tujunga Canyon floodplain. The dam also conserves runoff for drinking water and groundwater recharge. It saves Los Angeles about $2,250,000 per year. This is due to the cost difference between local and imported water.
Frequent dredging is needed because of the reservoir’s small storage capacity. The 2009 Station Fire burned 87% of the watershed. This caused over 2 million cubic yards of sediment to flow into the reservoir. All of this sediment had to be removed.
So, as we stand here, remember the Big Tujunga Number 1 Dam. It’s a blend of history, engineering, and community protection. The Big Tujunga Number 1 Dam is a guardian of the valley.