Upper Twin Lake
Key Takeaway
Upper Twin Lake is classified as low hazard in California. It was completed in 1987 and is 39 years old. Its primary use is water supply.
Physical Details
| Dam Height | 19 ft (taller than 14.1% in CA) |
| Dam Length | 350 ft |
| Dam Type | Earth |
| Max Storage | 63 acre-ft |
| Surface Area | 6 acres |
| Year Completed | 1987 (39 years old) |
| NID ID | CA01294 |
Safety Information
No probable loss of human life and low economic/environmental losses expected.
Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?
Ownership
Juliana Mutual Water Company
Private
Nearby Dams
Lower Twin Lake
Napa, CA
Low Hazard 18 ftDick Week
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Significant Hazard 70 ftDeer Creek
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Low Hazard 40 ftLong Valley West No. 2
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Low Hazard 35 ftReservoir 2
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High Hazard 14 ftHardester North
Napa, CA
Significant Hazard 36 ftDavis
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Significant Hazard 42 ftTurkey Ranch
Napa, CA
High Hazard 35 ftFrequently Asked Questions
What is the hazard classification of Upper Twin Lake?
Upper Twin Lake is classified as Low Hazard. No probable loss of human life and low economic/environmental losses expected. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.
Who owns and operates Upper Twin Lake?
Upper Twin Lake is owned by Juliana Mutual Water Company (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Upper Twin Lake built?
Upper Twin Lake was completed in 1987, making it 39 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 Upper Twin Lake?
Upper Twin Lake serves the following purposes: Water Supply, Irrigation, Recreation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Upper Twin Lake?
Upper Twin Lake has a dam height of 19 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 Upper Twin Lake last inspected?
Upper Twin Lake was last inspected on October 10, 2022. Inspection dates indicate when a formal review occurred, not the results of that inspection.