Del Valle
Del Valle is an earth dam located in Alameda County, California, built in 1968. It carries a High hazard potential classification and has a fair condition assessment.
About Del Valle
The primary purpose of Del Valle is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by California Department Of Water Resources (state). It impounds the Arroyo Valle near Livermore.
The dam stands 222 feet tall and stretches 880 feet across, creates a reservoir covering 710 acres, has a maximum storage capacity of 77,100 acre-feet, and collects water from a drainage area of 146 square miles. Completed in 1968, the structure is well into its service life at over 50 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 11/03/2025.
At 222 feet, this dam is taller than 99% of all dams in the United States.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The California dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | California |
| County | Alameda |
| Nearest City | Livermore |
| River/Stream | Arroyo Valle |
| Coordinates | 37.61570, -121.74500 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 222 ft |
| Dam Height | 222 ft |
| Dam Length | 880 ft |
| Year Completed | 1968 (58 years old) |
Storage & Hydraulics
| NID Storage | 77,100 acre-ft |
| Max Storage | 77,100 acre-ft |
| Surface Area | 710 acres |
| Drainage Area | 146 sq mi |
| Max Discharge | 47,000 cfs |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner | California Department of Water Resources |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 11/03/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00043 |
| Federal ID | CA00043 |
| More Info | State Dam Safety Program |