Alkali Detention Dam Reservoir Report
Last Updated: December 25, 2025
Alkali Detention Dam, located in Valley County, Montana, serves multiple purposes including fire protection, stock watering, and small fish pond management.
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Summary
Built in 1958 by the Bureau of Land Management, this gravity dam stands at a structural height of 14 feet, with a hydraulic height of 11 feet, and a length of 780 feet. The dam has a storage capacity of 94.9 acre-feet and covers a surface area of 19.59 acres, with a drainage area of 1.3 square miles.
Despite being classified as a low hazard potential structure, the condition assessment of Alkali Detention Dam is deemed unsatisfactory, with the last inspection conducted in October 2017. The dam features an uncontrolled spillway and is under federal ownership and regulation. As a part of the Milk River watershed, the dam helps manage water flow and mitigate flood risks in the region. With its strategic location and historical significance, Alkali Detention Dam stands as a vital resource for water management and climate resiliency efforts in Montana.
Year Completed |
1958 |
Dam Length |
780 |
River Or Stream |
WILLOW CK./MILK RIVER |
Primary Dam Type |
Gravity |
Surface Area |
19.59 |
Hydraulic Height |
11 |
Drainage Area |
1.3 |
Nid Storage |
94.9 |
Structural Height |
14 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
14 |
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.
Alkali Detention Dam