Halsey Afterbay
Key Takeaway
Halsey Afterbay is classified as high hazard in California. It was completed in 1913 and is 113 years old. Its primary use is hydroelectric. 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 | 38 ft (taller than 43.2% in CA) |
| Dam Length | 222 ft |
| Dam Type | Rockfill |
| Max Storage | 106 acre-ft |
| Normal Storage | 60 acre-ft |
| Surface Area | 9 acres |
| Drainage Area | 4 sq mi |
| Max Discharge | 2,830 cfs |
| Year Completed | 1913 (113 years old) |
| NID ID | CA00348 |
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
Pacific Gas and Electric Company
Private
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High Hazard 95 ftFrequently Asked Questions
What is the hazard classification of Halsey Afterbay?
Halsey 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 Halsey Afterbay?
Halsey Afterbay is owned by Pacific Gas and Electric Company (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Halsey Afterbay built?
Halsey Afterbay was completed in 1913, making it 113 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 Halsey Afterbay?
Halsey Afterbay serves the following purposes: Hydroelectric. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Halsey Afterbay?
Halsey Afterbay has a dam height of 38 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 Halsey Afterbay last inspected?
Halsey Afterbay was last inspected on August 7, 2023. Inspection dates indicate when a formal review occurred, not the results of that inspection.