Black Hills Power & Light First Enlargement Reservoir Report
Last Updated: December 5, 2025
The Black Hills Power & Light First Enlargement is a fascinating public utility dam located in Osage, Wyoming.
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Summary
Completed in 1940, this earth dam stands at a height of 27 feet and has a hydraulic height of 22 feet. With a storage capacity of 195 acre-feet and a surface area of 30 acres, this dam plays a crucial role in water resource management in the area.
Situated on the East Branch Poison Creek, the Black Hills Power & Light First Enlargement serves a primary purpose of "Other" and has a spillway width of 100 feet. Despite being classified as having a low hazard potential, the dam's condition is assessed as fair. With an inspection frequency of 5 years, the dam is closely monitored to ensure its safety and functionality. Its risk assessment is moderate, highlighting the importance of ongoing risk management measures.
Overall, the Black Hills Power & Light First Enlargement is a key infrastructure contributing to water resource management in Weston County, Wyoming. With its historical significance and continued operational importance, this dam serves as a testament to the vital role of dams in maintaining water security and climate resilience in the region.
Year Completed |
1940 |
Dam Length |
700 |
Dam Height |
27 |
River Or Stream |
EAST BRANCH POISON CREEK |
Primary Dam Type |
Earth |
Surface Area |
30 |
Hydraulic Height |
22 |
Nid Storage |
195 |
Structural Height |
27 |
Outlet Gates |
Valve - 1 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
27 |
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.
Black Hills Power & Light First Enlargement