Twin Lakes No. 1
Twin Lakes No. 1 is an earth dam located in Sheridan County, Wyoming, built in 1998. It carries a High hazard potential classification.
About Twin Lakes No. 1
The primary purpose of Twin Lakes No. 1 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 Sheridan - Tom Manolis (local government). It impounds the Coney Creek near Sheridan.
The dam stands 91 feet tall and stretches 1,835 feet across, creates a reservoir covering 81 acres, has a maximum storage capacity of 4,041 acre-feet, and collects water from a drainage area of 8 square miles. Completed in 1998, the structure is 28 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. An emergency action plan is in place for this dam. The most recent inspection on record was 08/20/2025.
At 91 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 Wyoming 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 | Wyoming |
| County | Sheridan |
| Nearest City | Sheridan |
| River/Stream | Coney Creek |
| Coordinates | 44.60960, -107.31320 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 91 ft |
| Dam Height | 84 ft |
| Dam Length | 1,835 ft |
| Year Completed | 1998 (28 years old) |
Storage & Hydraulics
| NID Storage | 4,041 acre-ft |
| Max Storage | 4,041 acre-ft |
| Normal Storage | 3,411 acre-ft |
| Surface Area | 81 acres |
| Drainage Area | 8 sq mi |
| Max Discharge | 13,540 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | CITY OF SHERIDAN - TOM MANOLIS |
| Owner Type | Local Government |
| Hazard Classification | High |
| Last Inspection | 08/20/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WY00647 |
| Federal ID | WY00647 |
| More Info | State Dam Safety Program |