Finale Detention Dam Reservoir Report
Nearby: Ruins Detention Dam Toprail Dam
Last Updated: December 21, 2025
Finale Detention Dam, located in Valley County, Montana, is a gravity dam with a primary purpose of flood risk reduction.
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Summary
Built in 1965 by the Bureau of Land Management, this dam on the South Fork Lone Tree river has a structural height of 34 feet and a hydraulic height of 24 feet. With a storage capacity of 74 acre-feet and a surface area of 15.45 acres, the dam plays a crucial role in controlling water flow and minimizing flooding in the surrounding area.
Despite its importance, Finale Detention Dam is currently assessed to be in poor condition, with a low hazard potential. The dam lacks a comprehensive emergency action plan and has not been regularly inspected, raising concerns about its ability to withstand potential risks. Given its moderate risk assessment rating, there is a need for improved risk management measures and regular maintenance to ensure the safety and effectiveness of the dam in mitigating flood events.
As a federally owned structure under the jurisdiction of the Bureau of Land Management, Finale Detention Dam serves as a vital asset in protecting the local community from flooding. However, with its current condition and risk assessment, there is a pressing need for enhanced maintenance and emergency preparedness to safeguard the dam's integrity and uphold its flood risk reduction function for the future.
Year Completed |
1965 |
Dam Length |
700 |
River Or Stream |
SOUTH FORK LONE TREE |
Primary Dam Type |
Gravity |
Surface Area |
15.45 |
Hydraulic Height |
24 |
Drainage Area |
0.5 |
Nid Storage |
74 |
Structural Height |
34 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
34 |
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.
Finale Detention Dam