Built in 1926, this earth dam stands at a height of 70 feet and has a maximum storage capacity of 300 acre-feet. Its primary purpose is for irrigation, serving the surrounding area by storing water from Three Mile Creek.
Despite its age, Three Mile Reservoir poses a high hazard potential due to its poor condition assessment. The dam has a drainage area of 5.6 square miles and a maximum discharge of 2600 cubic feet per second. The reservoir covers a surface area of 3 acres and has a normal storage capacity of 180 acre-feet. Its location in the Helena Valley makes it a critical water resource for the region.
With the Montana Department of Natural Resources and Conservation regulating its operations, Three Mile Reservoir remains under state jurisdiction for inspection, enforcement, and permitting. The dam is in need of maintenance and potential risk management measures to ensure its continued functionality and safety for the community that relies on it for irrigation water. For water resource and climate enthusiasts, the Three Mile Reservoir serves as an important example of the ongoing challenges faced in managing aging infrastructure in the face of changing environmental conditions.
Year Completed |
1926 |
Dam Length |
470 |
Dam Height |
70 |
River Or Stream |
THREE MILE CREEK |
Primary Dam Type |
Earth |
Surface Area |
3 |
Hydraulic Height |
50 |
Drainage Area |
5.6 |
Nid Storage |
300 |
Hazard Potential |
High |
Foundations |
Rock |
Nid Height |
70 |
| Location | Reservations | Toilets |
|---|---|---|
Fort Harrison RV Military - National Guard
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Cromwell Dixon
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Cromwell Dixon campground
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Moose Creek Cabin
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