Johnston
Key Takeaway
Johnston is classified as low hazard in California. It was completed in 1919 and is 107 years old. Its primary use is water supply.
Physical Details
| Dam Height | 31 ft (taller than 32.8% in CA) |
| Dam Length | 132 ft |
| Dam Type | Gravity |
| Max Storage | 30 acre-ft |
| Surface Area | 5 acres |
| Drainage Area | 8 sq mi |
| Year Completed | 1919 (107 years old) |
| NID ID | CA00667 |
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
Peninsula Open Space Trust
Private
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High Hazard 51 ftFrequently Asked Questions
What is the hazard classification of Johnston?
Johnston 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 Johnston?
Johnston is owned by Peninsula Open Space Trust (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Johnston built?
Johnston was completed in 1919, making it 107 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 Johnston?
Johnston serves the following purposes: Water Supply, Fire Protection, Stock, Or Small Fish Pond. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Johnston?
Johnston has a dam height of 31 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 Johnston last inspected?
Johnston was last inspected on June 22, 2022. Inspection dates indicate when a formal review occurred, not the results of that inspection.