Ralston Afterbay
Key Takeaway
Ralston Afterbay is classified as high hazard in California. It was completed in 1966 and is 60 years old. Its primary use is irrigation. High hazard means loss of life is likely if the dam fails — it does not indicate the dam's current condition. Learn more.
Physical Details
| Dam Height | 89 ft (taller than 79.1% in CA) |
| Dam Length | 560 ft |
| Dam Type | Concrete |
| Max Storage | 2.8K acre-ft |
| Normal Storage | 2.7K acre-ft |
| Surface Area | 83 acres |
| Drainage Area | 214 sq mi |
| Max Discharge | 159,000 cfs |
| Year Completed | 1966 (60 years old) |
| NID ID | CA00859 |
Safety Information
Loss of human life is likely if the dam fails.
Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?
Ownership
Placer County Water Agency
Local Government
Nearby Dams
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High Hazard 162 ftFrequently Asked Questions
What is the hazard classification of Ralston Afterbay?
Ralston Afterbay is classified as High Hazard. Loss of human life is likely if the dam fails. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.
Who owns and operates Ralston Afterbay?
Ralston Afterbay is owned by Placer County Water Agency (Local Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Ralston Afterbay built?
Ralston Afterbay was completed in 1966, making it 60 years old. Many U.S. dams were built between the 1930s and 1970s during a period of major infrastructure investment.
What is the primary purpose of Ralston Afterbay?
Ralston Afterbay serves the following purposes: Irrigation, Recreation, Hydroelectric, Water Supply. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Ralston Afterbay?
Ralston Afterbay has a dam height of 89 ft. Dam height is measured from the natural streambed at the downstream toe to the top of the dam, and may differ from the visible height.
When was Ralston Afterbay last inspected?
Ralston Afterbay was last inspected on August 23, 2023. Inspection dates indicate when a formal review occurred, not the results of that inspection.