Rock Creek Lake Reservoir Report

Last Updated: December 5, 2025

Rock Creek Lake is a private water supply reservoir located in Garrison, Montana.


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Summary

Built in 1960, this earth dam stands at a height of 30 feet and has a storage capacity of 2552 acre-feet. The primary purpose of Rock Creek Lake is water supply, serving as a vital resource for the local community in Powell County.

With a significant hazard potential, Rock Creek Lake is regulated by the Montana Department of Natural Resources and Conservation. Despite not having a current condition assessment, the dam is inspected, permitted, and enforced by state authorities to ensure its structural integrity and safety. The reservoir's location on Rock Creek, within the Seattle District of the US Army Corps of Engineers, highlights its importance in managing water resources and mitigating climate-related risks in the region.

For water resource and climate enthusiasts, Rock Creek Lake serves as a key infrastructure for water supply and management in Montana. Its history, design, and regulatory oversight provide valuable insights into the challenges and opportunities of sustaining vital water resources in a changing climate. As a significant reservoir with a crucial role in the local community, Rock Creek Lake exemplifies the importance of proactive management and investment in resilient water infrastructure.

Year Completed

1960

Dam Length

320

Dam Height

30

River Or Stream

ROCK CREEK

Primary Dam Type

Earth

Hydraulic Height

30

Nid Storage

2552

Hazard Potential

Significant

Nid Height

30
       
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.