Glacier Lake Dam Reservoir Report

Last Updated: December 5, 2025

Glacier Lake Dam, located in Missoula, Montana, is a local government-owned structure designed for water supply purposes.


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Summary

Completed in 1915, this earth dam stands at a height of 12 feet with a hydraulic height of 9 feet and a length of 210 feet. It has a storage capacity of 240 acre-feet, with a normal storage level of 210 acre-feet, serving as a vital resource for the surrounding community.

With a drainage area of 0.16 square miles and a maximum discharge of 100 cubic feet per second, Glacier Lake Dam poses a significant hazard potential. The spillway, with a width of 11 feet, is uncontrolled, and the outlet gates are also uncontrolled. Although the condition assessment is not rated, the risk assessment indicates a moderate risk level. The dam is regulated by the Montana Department of Natural Resources and Conservation (DNRC), with state inspection, permitting, and enforcement in place to ensure safety and compliance.

In the event of an emergency, Glacier Lake Dam's Emergency Action Plan (EAP) status is not specified, and there is no information on preparedness measures or guidelines. Despite these uncertainties, the dam continues to play a crucial role in water management and supply in the region, highlighting the importance of ongoing monitoring and risk management for water resource and climate enthusiasts alike.

Year Completed

1915

Dam Length

210

Dam Height

12

River Or Stream

TR-WRANGLE CREEK

Primary Dam Type

Earth

Surface Area

19

Hydraulic Height

9

Drainage Area

0.16

Nid Storage

240

Structural Height

12

Outlet Gates

Uncontrolled

Hazard Potential

Significant

Nid Height

12
       
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.