Grassy Lake
Key Takeaway
Grassy Lake is classified as high hazard in Wyoming. It was completed in 1938 and is 88 years old. Its primary use is irrigation. 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 | 118 ft (taller than 98.7% in WY) |
| Dam Length | 1,170 ft |
| Dam Type | Earth |
| Max Storage | 16.2K acre-ft |
| Normal Storage | 15.5K acre-ft |
| Surface Area | 318 acres |
| Drainage Area | 12 sq mi |
| Max Discharge | 675 cfs |
| Year Completed | 1938 (88 years old) |
| NID ID | WY01384 |
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
RECLAMATION
Federal Government
Frequently Asked Questions
What is the hazard classification of Grassy Lake?
Grassy Lake 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 Grassy Lake?
Grassy Lake is owned by RECLAMATION (Federal Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Grassy Lake built?
Grassy Lake was completed in 1938, making it 88 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 Grassy Lake?
Grassy Lake serves the following purposes: Irrigation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Grassy Lake?
Grassy Lake has a dam height of 118 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 Grassy Lake last inspected?
Grassy Lake was last inspected on July 29, 2020. Inspection dates indicate when a formal review occurred, not the results of that inspection.