Thornton Lake Dam is a rockfill dam located in Deer Lodge County, Montana, built in 1904. It carries a Significant hazard potential classification.
Dam profile
NID height · 11 ft11 ft tall and 315 ft long. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic rockfill embankment section and the water level is illustrative.
About Thornton Lake Dam
The primary purpose of Thornton Lake Dam is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Donald W Beck (private). It impounds the Thorton Creek near Deer Lodge.
The dam stands 11 feet tall and stretches 315 feet across, creates a reservoir covering 31 acres, has a storage capacity of 243 acre-feet, and collects water from a drainage area of 11 square miles. Completed in 1904, the structure is over a century old.
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. The most recent inspection on record was 08/11/2014. That was over 12 years ago.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Montana |
| County | Deer Lodge |
| Nearest City | Deer Lodge |
| River/Stream | Thorton Creek |
| Coordinates | 46.26016, -113.03469 |
Physical Characteristics
| Dam Type | Rockfill |
| NID Height | 11 ft |
| Dam Height | 11 ft |
| Dam Length | 315 ft |
| Year Completed | 1904 (122 years old) |
Storage & Hydraulics
| NID Storage | 243 acre-ft |
| Normal Storage | 243 acre-ft |
| Surface Area | 31 acres |
| Drainage Area | 11 sq mi |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | Donald W Beck |
| Owner Type | Private |
| Hazard Classification | Significant |
| Condition Assessment | Not assessed |
| Last Inspection | 08/11/2014 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MT01143 |
| Federal ID | MT01143 |
| More Info | State Dam Safety Program |