Three Mile Reservoir (L.&C.)

THREE MILE CREEK· Lewis and Clark, Montana· Built 1926· Earth· 70 ft tall
High Hazard Irrigation Private

Key Takeaway

Three Mile Reservoir (L.&C.) is classified as high hazard in Montana. It was completed in 1926 and is 100 years old. Its primary use is irrigation. High hazard means loss of life is likely if the dam fails — it does not indicate the dam's current condition. Learn more.

Physical Details

Dam Height 70 ft (taller than 98.3% in MT)
Dam Length470 ft
Dam TypeEarth
Max Storage300 acre-ft
Normal Storage180 acre-ft
Surface Area3 acres
Drainage Area6 sq mi
Max Discharge2,600 cfs
Year Completed1926 (100 years old)
NID IDMT00865

Safety Information

High Hazard

Loss of human life is likely if the dam fails.

Hazard potential describes downstream consequences of failure, not the dam's current condition. What does this mean?

Emergency Action Plan: Yes
Last Inspection: October 20, 2021
State Regulated: Yes
Regulatory Agency: DNRC

Ownership

DEBBIE WRIGHT

Private

Nearby Dams

Frequently Asked Questions

What is the hazard classification of Three Mile Reservoir (L.&C.)?

Three Mile Reservoir (L.&C.) is classified as High Hazard. Loss of human life is likely if the dam fails. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.

Who owns and operates Three Mile Reservoir (L.&C.)?

Three Mile Reservoir (L.&C.) is owned by DEBBIE WRIGHT (Private). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Three Mile Reservoir (L.&C.) built?

Three Mile Reservoir (L.&C.) was completed in 1926, making it 100 years old. Many U.S. dams were built between the 1930s and 1970s during a period of major infrastructure investment.

What is the primary purpose of Three Mile Reservoir (L.&C.)?

Three Mile Reservoir (L.&C.) serves the following purposes: Irrigation. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.

How tall is Three Mile Reservoir (L.&C.)?

Three Mile Reservoir (L.&C.) has a dam height of 70 ft. Dam height is measured from the natural streambed at the downstream toe to the top of the dam, and may differ from the visible height.

When was Three Mile Reservoir (L.&C.) last inspected?

Three Mile Reservoir (L.&C.) was last inspected on October 20, 2021. Inspection dates indicate when a formal review occurred, not the results of that inspection.

Data from the National Inventory of Dams (NID) maintained by the US Army Corps of Engineers. Dam conditions may have changed since the last update. This site is not affiliated with USACE. Do not use for emergency planning — contact your local dam safety program.