Alder
Key Takeaway
Alder is classified as high hazard in Washington. It was completed in 1945 and is 81 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 | 285 ft (taller than 87% in WA) |
| Dam Length | 1,487 ft |
| Dam Type | Concrete |
| Max Storage | 241.2K acre-ft |
| Normal Storage | 214.5K acre-ft |
| Surface Area | 3,065 acres |
| Drainage Area | 286 sq mi |
| Max Discharge | 80,000 cfs |
| Year Completed | 1945 (81 years old) |
| NID ID | WA00257 |
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
City of Tacoma
Public Utility
Nearby Dams
Frequently Asked Questions
What is the hazard classification of Alder?
Alder 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 Alder?
Alder is owned by City of Tacoma (Public Utility). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Alder built?
Alder was completed in 1945, making it 81 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 Alder?
Alder serves the following purposes: Hydroelectric, Recreation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Alder?
Alder has a dam height of 285 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 Alder last inspected?
Alder was last inspected on January 23, 2023. Inspection dates indicate when a formal review occurred, not the results of that inspection.