Nilan North Dam
Nilan North Dam is an earth dam located in Lewis and Clark County, Montana, built in 1951. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Nilan North Dam
The primary purpose of Nilan North Dam is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by State Water Projects (state). It impounds the Tr-willow Creek near Sun River.
The dam stands 54 feet tall and stretches 530 feet across, creates a reservoir covering 525 acres, has a maximum storage capacity of 15,600 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1951, the structure is well into its service life at over 50 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 04/30/2024.
At 54 feet, this dam is taller than 94% of dams nationwide.
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 Montana 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 | Montana |
| County | Lewis and Clark |
| Nearest City | Sun River |
| River/Stream | Tr-willow Creek |
| Coordinates | 47.48690, -112.53890 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 54 ft |
| Dam Height | 54 ft |
| Dam Length | 530 ft |
| Year Completed | 1951 (75 years old) |
Storage & Hydraulics
| NID Storage | 15,600 acre-ft |
| Max Storage | 15,600 acre-ft |
| Normal Storage | 10,092 acre-ft |
| Surface Area | 525 acres |
| Drainage Area | 3 sq mi |
| Max Discharge | 395 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | STATE WATER PROJECTS |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 04/30/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MT03206 |
| Federal ID | MT03206 |
| More Info | State Dam Safety Program |