Cogswell
Key Takeaway
Cogswell is classified as high hazard in California. It was completed in 1935 and is 91 years old. Its primary use is flood risk reduction. 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 | 266 ft (taller than 97.7% in CA) |
| Dam Length | 585 ft |
| Dam Type | Rockfill |
| Max Storage | 9.0K acre-ft |
| Surface Area | 146 acres |
| Drainage Area | 38 sq mi |
| Year Completed | 1935 (91 years old) |
| NID ID | CA00190 |
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
Los Angeles County Department Of Public Works
Local Government
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High Hazard 43 ftFrequently Asked Questions
What is the hazard classification of Cogswell?
Cogswell 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 Cogswell?
Cogswell is owned by Los Angeles County Department Of Public Works (Local Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Cogswell built?
Cogswell was completed in 1935, making it 91 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 Cogswell?
Cogswell serves the following purposes: Flood Risk Reduction, Irrigation, Hydroelectric, Water Supply. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Cogswell?
Cogswell has a dam height of 266 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 Cogswell last inspected?
Cogswell was last inspected on October 27, 2021. Inspection dates indicate when a formal review occurred, not the results of that inspection.