Square Butte Detention Dam Reservoir Report

Last Updated: December 5, 2025

Square Butte Detention Dam, located in Fort Peck, Montana, is a Federal-owned structure managed by the Bureau of Land Management.


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Summary

Completed in 1967, this gravity dam stands at a structural height of 42 feet and serves the primary purpose of flood risk reduction along the Rock Creek and Missouri River. With a storage capacity of 396.93 acre-feet and a surface area of 26.2 acres, the dam plays a crucial role in mitigating flood risks in the region.

Despite its importance in flood control, the Square Butte Detention Dam is currently assessed as being in poor condition, with a low hazard potential. The dam's spillway type is uncontrolled, and it has a hydraulic height of 35 feet. The structure is inspected every 5 years, with the last inspection conducted in August 2016. While the risk assessment for the dam indicates a moderate level of risk, the Bureau of Land Management continues to monitor and manage the structure to ensure its safety and effectiveness in protecting the surrounding area from potential flooding events.

Overall, Square Butte Detention Dam stands as a vital asset in the flood risk reduction infrastructure of Phillips County, Montana. With its strategic location and design, the dam plays a crucial role in safeguarding the community against potential water-related emergencies. Ongoing monitoring and maintenance efforts by the Bureau of Land Management are essential to ensure the continued reliability and resilience of this important water resource infrastructure.

Year Completed

1967

Dam Length

455

River Or Stream

ROCK CK./MISSOURI RIVER

Primary Dam Type

Gravity

Surface Area

26.2

Hydraulic Height

35

Drainage Area

6.3

Nid Storage

396.93

Structural Height

42

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

42
       
Seasonal Comparison

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Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.