Gem State
Key Takeaway
Gem State is classified as high hazard in Idaho. It was completed in 1988 and is 38 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 | 40 ft (taller than 70.7% in ID) |
| Dam Length | 1,136 ft |
| Dam Type | Concrete |
| Max Storage | 6.7K acre-ft |
| Normal Storage | 5.0K acre-ft |
| Surface Area | 305 acres |
| Drainage Area | 4,650 sq mi |
| Max Discharge | 140,000 cfs |
| Year Completed | 1988 (38 years old) |
| NID ID | ID83006 |
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 Idaho Falls
Local Government
Nearby Dams
Gem State Right Dike
Bonneville, ID
High Hazard 30 ftGem State Left Dike
Bonneville, ID
High Hazard 30 ftLower Diversion
Bonneville, ID
Low Hazard 14 ftCity Diversion
Bonneville, ID
Low Hazard 30 ftIdaho Falls Upper Diversion Dam No 1
Bonneville, ID
Low Hazard 28 ftUpper Diversion Dam #2
Bonneville, ID
Low Hazard 33 ftIdaho Falls Upper Powerhouse Dam No 2
Bonneville, ID
Low Hazard 37 ftUpper Diversion Dam #1
Bonneville, ID
Low Hazard 23 ftFrequently Asked Questions
What is the hazard classification of Gem State?
Gem State 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 Gem State?
Gem State is owned by City of Idaho Falls (Local Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.
When was Gem State built?
Gem State was completed in 1988, making it 38 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 Gem State?
Gem State serves the following purposes: Hydroelectric, Irrigation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.
How tall is Gem State?
Gem State has a dam height of 40 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 Gem State last inspected?
Gem State was last inspected on October 18, 2022. Inspection dates indicate when a formal review occurred, not the results of that inspection.