Big Lake
Big Lake is an earth dam located in Missoula County, Montana, built in 1915. It carries a Significant hazard potential classification.
About Big Lake
The primary purpose of Big Lake 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 Missoula (local government). It impounds the Tr-lake Creek near Missoula.
The dam stands 30 feet tall and stretches 440 feet across, creates a reservoir covering 38 acres, has a maximum storage capacity of 621 acre-feet, and collects water from a drainage area of 4 square miles. Completed in 1915, 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 08/01/2017.
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Location
| State | Montana |
| County | Missoula |
| Nearest City | Missoula |
| River/Stream | Tr-lake Creek |
| Coordinates | 47.03974, -113.91598 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 30 ft |
| Dam Height | 30 ft |
| Dam Length | 440 ft |
| Year Completed | 1915 (111 years old) |
Storage & Hydraulics
| NID Storage | 621 acre-ft |
| Max Storage | 621 acre-ft |
| Normal Storage | 143 acre-ft |
| Surface Area | 38 acres |
| Drainage Area | 4 sq mi |
| Max Discharge | 95 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | CITY OF MISSOULA |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Last Inspection | 08/01/2017 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MT01465 |
| Federal ID | MT01465 |
| More Info | State Dam Safety Program |