Big Rock Detention Dam

WILLOW CK./MILK RIVER· Valley, Montana· Built 1961· Gravity·
Low Hazard Flood Risk Reduction Federal Government

Key Takeaway

Big Rock Detention Dam is classified as low hazard in Montana. It was completed in 1961 and is 65 years old. Its primary use is flood risk reduction.

Physical Details

Dam Length1,793 ft
Dam TypeGravity
Max Storage265 acre-ft
Normal Storage0 acre-ft
Surface Area62 acres
Drainage Area0 sq mi
Year Completed1961 (65 years old)
NID IDMT00711

Safety Information

Low Hazard

No probable loss of human life and low economic/environmental losses expected.

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

Emergency Action Plan: No
Last Inspection: November 2, 2019
State Regulated: No

Ownership

DOI BLM

Federal Government

Nearby Dams

Frequently Asked Questions

What is the hazard classification of Big Rock Detention Dam?

Big Rock Detention Dam is classified as Low Hazard. No probable loss of human life and low economic/environmental losses expected. This classification refers to the potential downstream consequences of a failure, not the dam's current structural condition.

Who owns and operates Big Rock Detention Dam?

Big Rock Detention Dam is owned by DOI BLM (Federal Government). The owner is responsible for maintenance, inspections, and compliance with dam safety regulations.

When was Big Rock Detention Dam built?

Big Rock Detention Dam was completed in 1961, making it 65 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 Big Rock Detention Dam?

Big Rock Detention Dam serves the following purposes: Flood Risk Reduction. Many dams in the U.S. are multi-purpose, supporting flood control, water supply, recreation, and other uses.

When was Big Rock Detention Dam last inspected?

Big Rock Detention Dam was last inspected on November 2, 2019. 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.