East Fork Dam Reservoir Report
Nearby: Hanson Creek Dam Pike Creek Dam
Last Updated: December 5, 2025
East Fork Dam, located in Lewistown, Montana, is a key structure designed by the USDA NRCS for flood risk reduction and recreation purposes.
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Summary
Completed in 1974, this earth dam stands at a height of 62 feet and has a structural height of 93 feet, providing a normal storage capacity of 1700 acre-feet for the East Fork Big Spring Creek. With a drainage area of 60.8 square miles and a maximum discharge of 28500 cubic feet per second, the dam plays a crucial role in managing water resources in the region.
This high-hazard potential dam with a satisfactory condition assessment is regulated by the DNRC and undergoes regular inspections every 5 years, with the last assessment conducted in June 2020. Despite its risk level being moderate, the dam has no Emergency Action Plan (EAP) in place, raising concerns about preparedness for potential emergencies. With a spillway width of 400 feet and uncontrolled outlet gates, East Fork Dam continues to be a significant feature in the water resource management and climate adaptation efforts in Fergus County, Montana.
Surrounded by the natural beauty of Fergus County, East Fork Dam offers recreational opportunities while serving as a critical infrastructure for flood control. Its stone core and soil foundation contribute to the dam's resilience, ensuring the safety of nearby communities. As climate change impacts intensify, the maintenance and management of East Fork Dam will be crucial in safeguarding the region's water resources and enhancing resilience to extreme weather events.
Year Completed |
1974 |
Dam Length |
2179 |
Dam Height |
62 |
River Or Stream |
EAST FORK BIG SPRING CREEK |
Primary Dam Type |
Earth |
Surface Area |
201 |
Hydraulic Height |
62 |
Drainage Area |
60.8 |
Nid Storage |
7150 |
Structural Height |
93 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
High |
Foundations |
Soil |
Nid Height |
93 |
Seasonal Comparison
Weather Forecast
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.
East Fork Dam