Mammoth Reservoir
Key Takeaway
Mammoth Reservoir is classified as high hazard in California. It was completed in 1851 and is 175 years old. Its primary use is other. 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 | 23 ft (taller than 21.2% in CA) |
| Dam Length | 2,360 ft |
| Dam Type | Earth |
| Max Storage | 103 acre-ft |
| Surface Area | 11 acres |
| Drainage Area | 0 sq mi |
| Year Completed | 1851 (175 years old) |
| NID ID | CA00861 |
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
Clover Valley
Placer, CA
Low Hazard 35 ftWise Forebay
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High Hazard 20 ftMiners Ravine Detention
Placer, CA
Low Hazard 23 ftHinkle
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High Hazard 20 ftFolsom
Sacramento, CA
High Hazard 275 ftAeree
El Dorado, CA
Significant Hazard 35 ftMount Stoneman
Sacramento, CA
Low Hazard 43 ftRock Creek
Placer, CA
High Hazard 36 ftFrequently Asked Questions
What is the hazard classification of Mammoth Reservoir?
Mammoth Reservoir 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 Mammoth Reservoir?
Mammoth Reservoir is owned by Placer County Water Agency (Local Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Mammoth Reservoir built?
Mammoth Reservoir was completed in 1851, making it 175 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 Mammoth Reservoir?
Mammoth Reservoir serves the following purposes: Other, Irrigation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Mammoth Reservoir?
Mammoth Reservoir has a dam height of 23 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 Mammoth Reservoir last inspected?
Mammoth Reservoir was last inspected on December 20, 2021. Inspection dates indicate when a formal review occurred, not the results of that inspection.