No. 5a Reservoir Report
Nearby: No. 4 Pond No. 3
Last Updated: December 15, 2025
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Summary
5a, also known as the Enl of 7687r, is a private earth dam located in Sweetwater, Wyoming, near the Flaming Gorge Reservoir. Constructed in 1975 by designer Frank J. Trelease, this dam serves primarily for tailings storage, with a height of 58 feet and a hydraulic height of 52 feet. It spans 3,500 feet in length and has a storage capacity of 5,556 acre-feet, making it a key structure for managing water resources in the area.
The dam's spillway, operating as uncontrolled with a width of 30 feet, ensures the safe release of water during peak flows. Despite its low hazard potential and fair condition assessment, the dam undergoes inspections every five years to ensure its integrity and resilience. With a moderate risk assessment rating, No. 5a represents a crucial component of water resource infrastructure in Wyoming, playing a vital role in mitigating flood risks and safeguarding downstream communities along the Allied Draw river.
Owned and regulated by private entities, this earth dam stands as a testament to engineering excellence and effective water management practices. Its strategic location near the Flaming Gorge Reservoir underscores its importance in the region's water supply and storage network. As climate change continues to impact water resources, No. 5a serves as a critical asset in ensuring the resilience and sustainability of Wyoming's water infrastructure for future generations of water resource and climate enthusiasts.
Year Completed |
1975 |
Dam Length |
3500 |
Dam Height |
58 |
River Or Stream |
ALLIED DRAW |
Primary Dam Type |
Earth |
Surface Area |
200 |
Hydraulic Height |
52 |
Drainage Area |
200.5 |
Nid Storage |
5556 |
Structural Height |
70 |
Outlet Gates |
Slide (sluice gate) - 1 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
70 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Blacks Fork Near Little America
|
14cfs |
Green River Near Green River
|
870cfs |
Green River Below Fontenelle Reservoir
|
852cfs |
Henrys Fork Near Manila
|
49cfs |
Pacific Creek Near Farson
|
3cfs |
Green River Near La Barge
|
681cfs |
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.
No. 5a