Green Hills Reservoir Report
Last Updated: December 7, 2025
Green Hills in Washakie, Wyoming, is a local government-owned dam designed by John Donnell for irrigation purposes.
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Summary
Completed in 1971, this earth dam stands at 17 feet high and spans 588 feet in length, with a storage capacity of 115 acre-feet. The dam on the Runway Draw river provides water for irrigation and recreation, with a spillway width of 20 feet and a maximum discharge of 337 cubic feet per second. Despite its low hazard potential and fair condition assessment, the dam undergoes inspections every five years to ensure its safety and functionality.
Located in Manderson, Green Hills dam plays a crucial role in managing water resources in the area, covering a surface area of 10 acres and draining a 2.5-square-mile watershed. With its stone core and soil foundation, the dam is regulated by the State Engineer's Office in Wyoming and meets state permitting, inspection, and enforcement requirements. While the dam has a moderate risk assessment rating, there are no designated emergency action plans or inundation maps prepared at present, emphasizing the need for ongoing risk management measures and updates to ensure the safety of the surrounding community and environment.
Year Completed |
1971 |
Dam Length |
588 |
Dam Height |
17 |
River Or Stream |
RUNWAY DRAW |
Primary Dam Type |
Earth |
Surface Area |
10 |
Hydraulic Height |
15 |
Drainage Area |
2.5 |
Nid Storage |
115 |
Structural Height |
17 |
Outlet Gates |
Slide (sluice gate) - 0 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
17 |
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.
Green Hills