Spinney Mountain
Spinney Mountain is an earth dam located in Park County, Colorado, built in 1982. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Spinney Mountain
The primary purpose of Spinney Mountain is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by City Of Aurora (local government). It impounds the South Platte River near Lake George.
The dam stands 100 feet tall and stretches 4,125 feet across, creates a reservoir covering 2,450 acres, has a maximum storage capacity of 83,300 acre-feet, and collects water from a drainage area of 772 square miles. Completed in 1982, the structure is 44 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. 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 07/19/2022.
At 100 feet, this dam is taller than 98% of all dams in the United States.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Colorado dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Colorado |
| County | Park |
| Nearest City | Lake George |
| River/Stream | South Platte River |
| Coordinates | 38.97168, -105.62195 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 100 ft |
| Dam Height | 90 ft |
| Dam Length | 4,125 ft |
| Year Completed | 1982 (44 years old) |
Storage & Hydraulics
| NID Storage | 83,300 acre-ft |
| Max Storage | 83,300 acre-ft |
| Normal Storage | 53,873 acre-ft |
| Surface Area | 2,450 acres |
| Drainage Area | 772 sq mi |
| Max Discharge | 104,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | CITY OF AURORA |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 07/19/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CO02677 |
| Federal ID | CO02677 |
| More Info | State Dam Safety Program |