Upper Lake Mary
Upper Lake Mary is an earth dam located in Coconino County, Arizona, built in 1941. It carries a Significant hazard potential classification and has a satisfactory condition assessment.
About Upper Lake Mary
The primary purpose of Upper Lake Mary is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by City Of Flagstaff (local government). It impounds the Walnut Creek near Walnut Canyon National Monument & I-40.
The dam stands 49 feet tall and stretches 845 feet across, creates a reservoir covering 1,058 acres, has a maximum storage capacity of 21,041 acre-feet, and collects water from a drainage area of 54 square miles. Completed in 1941, the structure is well-established, with more than 75 years of service.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 09/18/2024.
At 49 feet, this dam is taller than 92% of dams nationwide.
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Location
| State | Arizona |
| County | Coconino |
| Nearest City | Walnut Canyon National Monument & I-40 |
| River/Stream | Walnut Creek |
| Coordinates | 35.08083, -111.53361 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 49 ft |
| Dam Height | 38 ft |
| Dam Length | 845 ft |
| Year Completed | 1941 (85 years old) |
Storage & Hydraulics
| NID Storage | 21,041 acre-ft |
| Max Storage | 21,041 acre-ft |
| Normal Storage | 16,576 acre-ft |
| Surface Area | 1,058 acres |
| Drainage Area | 54 sq mi |
| Max Discharge | 11,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | CITY OF FLAGSTAFF |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Satisfactory |
| Last Inspection | 09/18/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | AZ00016 |
| Federal ID | AZ00016 |
| More Info | State Dam Safety Program |