Peterson Lake Reservoir Report

Last Updated: December 5, 2025

Peterson Lake, located in Missoula, Montana, is a privately owned water resource managed for irrigation purposes.


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Summary

The earth dam, standing at 12 feet high with a storage capacity of 170 acre-feet, was completed in 1920 along the TR-Rattlesnake Creek. With a low hazard potential and no current condition rating, the dam plays a crucial role in supporting agricultural activities in the region.

Despite being under state jurisdiction and regulation by the Department of Natural Resources and Conservation (DNRC), Peterson Lake has not been rated for its condition assessment. While it has not been inspected recently and lacks an Emergency Action Plan (EAP), the dam remains a vital infrastructure for water storage and distribution in the area. The risk management measures and preparedness for potential emergencies are areas that could be improved for the long-term sustainability of the dam.

With its location in the beautiful city of Missoula and its importance for irrigation, Peterson Lake serves as a significant water resource for the community. As climate change continues to impact water availability and usage patterns, ensuring the safety and efficiency of dams like Peterson Lake will be crucial for adapting to the changing environmental conditions and maintaining a reliable water supply for agricultural activities in the region.

Year Completed

1920

Dam Length

150

Dam Height

12

River Or Stream

TR-RATTLESNAKE CREEK

Primary Dam Type

Earth

Hydraulic Height

9

Nid Storage

170

Hazard Potential

Low

Nid Height

12
       
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.