Why Invest in Dam Safety?
California can protect public safety and enhance the State’s climate resilience by allocating substantial funding for public safety projects at existing dams, including repairs, reinforcements, seismic upgrades and new spillways.
As detailed in “State High Risk,” the California State Auditor’s updated assessment of high-risk issues faced by the State released in 2020:
“Aging water infrastructure within the State continues to threaten public safety. Specifically, inadequately maintained dams or those not meeting standards, especially those whose failure could affect large populations, pose significant risks to California residents.”Many of these aging facilities present public safety risks and cannot provide their intended water supply benefit because they have been forced to operate at levels significantly below their full design capacities.
The impacts of climate change on California’s hydrology also will require improvements to existing dams and their associated facilities to ensure that they can provide flood protection benefits now and into the future.
Half of the state’s 1,250 dams are classified as “high” or “extremely high” downstream hazard risks by the California Division of Safety of Dams.
California's 2023-24 budget package established a new State program, the "Dam Safety and Climate Resilience Local Assistance Program," (SB 122, Section 35) to provide funding assistance to local dam safety projects and appropriated $100 million in initial funding for the program.
There is a multi-billion-dollar need for state and federal investment in the improvement of existing dams in California. Failure to invest in these critical upgrades will result in impacts, including increasingly unaffordable water rates.
Examples of Dam Safety Projects
1. Anderson Dam Seismic Retrofit Project
Santa Clara County
Estimated Project Cost: $2.3 billion
A large earthquake on nearby faults could result in significant damage to Anderson Dam, possibly leading to dam failure and an uncontrolled water release that could inundate cities and rural areas from San Francisco Bay south to Monterey Bay, including much of Silicon Valley. The Santa Clara Valley Water District (Valley Water) is working closely with federal and State regulators on this project to fully remove and replace the dam.
The now drained reservoir had a capacity of nearly 90,000 acre-feet, enough water to supply a million people for a year. It is the largest in Santa Clara County, and its reconstruction is critical to the regional water supply system. Valley Water is moving expeditiously to remove and replace the existing dam as well as construct a new dam outlet and necessary downstream flood, groundwater recharge and environmental improvements.
2. Atmospheric River Control Spillway at New Bullards Bar Dam
Yuba County
Estimated Project Cost: $240 million
Yuba Water Agency is designing a new, second spillway for New Bullards Bar Dam – the state’s second tallest dam, with a reservoir capacity of approximately one million acre-feet. The ARC spillway will have gates 31.5 feet lower in elevation, which will significantly reduce flood risk for approximately 100,000 downstream residents along the Yuba and Feather rivers.
The lower gates will improve operational flexibility, allowing for water releases in advance of large, threatening storm events, during periods when there is enough downstream channel capacity to handle increased flows. The ARC Spillway will protect nearly $1 billion in levee improvement investments made by the State, federal and local governments over the last 20 years by reducing river elevations and pressure on levees during high flow events.
3. San Antonio and Nacimiento Dams Repair/Rehabilitation
San Luis Obispo County and Monterey County
Estimated Project Cost: $145 million
Monterey CountyWaterResources Agency (MCWRA) owns and operates the Nacimiento and San Antonio dams and reservoirs. These two dams provide flood protection and groundwater recharge to more than 418,000 acres, with much of the acreage supporting a $4 billion agricultural industry in the Salinas Valley. Included in this area is a population of over 200,000 people in cities and towns like King City, Gonzales, Soledad and Salinas, as well as rural areas that utilize groundwater as the primary drinking water supply.
MCWRA currently has self-imposed operational criteria in place for these facilities and, without improvements, it is possible that further water storage limitations will be required, impacting MCWRA’s ability to provide reservoir releases necessary for groundwater recharge and municipal, industrial, and irrigation water supply wells.
4. Lake Hodges Dam Repair/Rehabilitation
San Diego County
Estimated Project Cost: $275-300 million
Owned by the City of San Diego, Lake Hodges Dam was constructed between 1917-1919 and has a reservoir capacity of 30,633 acre-ft. The dam is located on the San Dieguito River near Escondido and has an “extremely high” downstream hazard classification from DSOD. Hodges Reservoir is the main source of local water for Santa Fe Irrigation District. Other local water suppliers also hold water rights in Lake Hodges.
In August 2019, DSOD imposed a water level restriction for Lake Hodges, which resulted in a 57% reduction in the reservoir’s capacity. This restriction significantly reduces the ability of the districts to store local water supplies and reduces the regional emergency storage levels protecting San Diego County in the event of disruption of the imported water system or due to a catastrophic event such as an earthquake.
For more information, please contact:
Danielle Blacet‑Hyden, California Municipal Utilities Association, dblacet@cmua.org
Dam Safety in the News
These 42 California dams need repairs. But lawmakers cut the funds in half - Cal MattersThe Trillion-Gallon Question - The New York Times Magazine
California’s aging dams face new perils, 50 years after Sylmar quake crisis – The Los Angeles Times
San Diego to spend $100M to figure out how to fix its aging, vulnerable dams - San Diego Union Tribune
San Diego releases 600 million gallons from lake due to dam safety fears – Newsweek
Anderson Dam costs triple, to $2.3 billion – San Jose Inside