Windmill No. 1 Reservoir Report
Nearby: Ballard No. 4 Fred No. 1
Last Updated: December 7, 2025
Windmill No.
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Summary
1, located in Niobrara, Wyoming, is a privately owned earth dam completed in 1956 that serves multiple purposes including fire protection, stock watering, and small fish pond management. Standing at a structural height of 50 feet with a hydraulic height of 45 feet, this dam has a storage capacity of 649 acre-feet and covers a surface area of 29 acres. The dam is situated on the SOUTH FORK WINDMILL DRAW, in close proximity to Edgemont, SD, making it a vital resource for the local community.
Despite being classified as low hazard potential, Windmill No. 1 received a fair condition assessment during its last inspection in April 2017. The dam features an uncontrolled spillway with a width of 100 feet and is equipped with a single valve outlet gate. With a moderate risk assessment rating of 3, there is ongoing monitoring and management of potential risks associated with the dam. It is noteworthy that the dam is not under the jurisdiction of the US Army Corps of Engineers, indicating that local regulatory agencies such as the State Engineer's Office oversee its permitting, inspection, and enforcement activities. For water resource and climate enthusiasts, Windmill No. 1 stands as a testament to the importance of small-scale dams in providing essential water management functions within rural communities.
Year Completed |
1956 |
Dam Length |
763 |
Dam Height |
50 |
River Or Stream |
SOUTH FORK WINDMILL DRAW |
Primary Dam Type |
Earth |
Surface Area |
29 |
Hydraulic Height |
45 |
Nid Storage |
649 |
Structural Height |
50 |
Outlet Gates |
Valve - 1 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
50 |
Seasonal Comparison
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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.
Windmill No. 1