Magnesia Reservoir Report
Nearby: Mincoff Reservoir #1 Mincoff #2
Last Updated: December 6, 2025
Magnesia, located in Cohagen, Montana, is a privately owned earth dam completed in 1960 for fire protection, stock, and small fish pond purposes.
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Summary
Situated on Phillips Creek in Garfield County, this dam has a height of 12 feet and a storage capacity of 53 acre-feet, with a normal storage level of 22 acre-feet. With a low hazard potential and a lack of recent condition assessments, Magnesia remains ungraded in terms of its current condition.
Despite its modest size and purpose, Magnesia is regulated by the Montana Department of Natural Resources and Conservation (DNRC) and meets state permitting, inspection, and enforcement requirements. The dam is located in Congressional District 00, represented by Greg Gianforte (R), and falls under the jurisdiction of the Omaha District of the US Army Corps of Engineers. While the dam has not been modified in recent years and lacks detailed risk assessment and emergency preparedness information, its compliance with state regulations ensures it serves its intended functions effectively.
Water resource and climate enthusiasts interested in Magnesia can appreciate its historical significance as a vital structure for fire protection and livestock management in the area. As a privately owned dam with a specific yet crucial purpose, its location on Phillips Creek adds to the ecological diversity of the region. Although lacking detailed information on its current condition and risk management measures, Magnesia's low hazard potential and state regulation ensure it continues to contribute positively to the local environment and community.
Year Completed |
1960 |
Dam Length |
275 |
Dam Height |
12 |
River Or Stream |
PHILLIPS CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
12 |
Nid Storage |
53 |
Hazard Potential |
Low |
Nid Height |
12 |
Seasonal Comparison
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Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Magnesia