Tarawa Retention Dam Reservoir Report

Last Updated: December 5, 2025

The Tarawa Retention Dam, located in Hinsdale, Montana, stands as a crucial federal structure managed by the Bureau of Land Management.


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Summary

Completed in 1947, this gravity dam serves multiple purposes such as fire protection, livestock maintenance, and creating a small fish pond. With a hydraulic height of 17 feet and a structural height of 22 feet, the dam boasts a storage capacity of 55.6 acre-feet, with normal storage levels at 29.8 acre-feet. The dam's controlled spillway and low hazard potential make it an essential asset for water resource management in the region.

Despite its importance, the Tarawa Retention Dam currently faces challenges with a poor condition assessment, indicating a need for maintenance and upgrades. The risk assessment categorizes the structure as having a very high risk level, emphasizing the urgency for potential risk management measures to be implemented. The dam's unique design incorporating a buttress and stone core, spanning 1025 feet in length, showcases its historical significance in enhancing water resource sustainability in the Cottonwood Creek/Milk River watershed. Enthusiasts of water resources and climate resilience would find the Tarawa Retention Dam an intriguing case study for exploring the intersection of infrastructure management, environmental stewardship, and community safety in the face of changing climate conditions.

Year Completed

1947

Dam Length

1025

River Or Stream

COTTONWOOD CK./MILK RIVER

Primary Dam Type

Gravity

Surface Area

17.2

Hydraulic Height

17

Drainage Area

4

Nid Storage

55.6

Structural Height

22

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

22
       
Seasonal Comparison

Weather Forecast

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.