Masonry Dam
Key Takeaway
Masonry Dam is classified as high hazard in Washington. It was completed in 1914 and is 112 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 Length | 980 ft |
| Dam Type | Arch |
| Max Storage | 175.0K acre-ft |
| Normal Storage | 90.7K acre-ft |
| Surface Area | 280 acres |
| Drainage Area | 81 sq mi |
| Max Discharge | 74,400 cfs |
| Year Completed | 1914 (112 years old) |
| NID ID | WA00255 |
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
Seattle City Light
Public Utility
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High HazardFrequently Asked Questions
What is the hazard classification of Masonry Dam?
Masonry Dam 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 Masonry Dam?
Masonry Dam is owned by Seattle City Light (Public Utility). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Masonry Dam built?
Masonry Dam was completed in 1914, making it 112 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 Masonry Dam?
Masonry Dam serves the following purposes: Hydroelectric, Water Supply. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
When was Masonry Dam last inspected?
Masonry Dam was last inspected on July 22, 2023. Inspection dates indicate when a formal review occurred, not the results of that inspection.