Eliasson (Petroleum) Reservoir Report

Last Updated: December 5, 2025

Eliasson (Petroleum) is a privately owned dam located in Mosby, Montana, specifically in Petroleum County.


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Summary

Built in 1939, this earth dam stands at a height of 19.2 feet and serves multiple purposes including fire protection, stock, and small fish pond. With a normal storage capacity of 400 acre-feet and a surface area of 35 acres, Eliasson (Petroleum) plays a crucial role in water resource management in the region.

Situated on TR-Little Wall Creek, this dam is regulated by the Montana Department of Natural Resources and Conservation (DNRC) and is subject to state inspections and enforcement. Despite its low hazard potential, the condition assessment of Eliasson (Petroleum) is currently not rated, indicating a need for further evaluation. The dam's proximity to the Congressional District 00 of Montana, represented by Greg Gianforte, highlights its importance in ensuring water security and safety for the surrounding communities.

As climate change continues to impact water resources, dams like Eliasson (Petroleum) play a vital role in mitigating risks and providing essential services. With a history dating back to the late 1930s, this dam stands as a testament to the enduring importance of water infrastructure in sustaining ecosystems and supporting human activities. As water resource and climate enthusiasts, understanding the significance of dams like Eliasson (Petroleum) is crucial for promoting sustainable water management practices in the face of a changing environment.

Year Completed

1939

Dam Length

545

Dam Height

19.2

River Or Stream

TR-LITTLE WALL CREEK

Primary Dam Type

Earth

Surface Area

35

Hydraulic Height

14.4

Drainage Area

38.13

Nid Storage

400

Hazard Potential

Low

Nid Height

19
       
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.