Thunder Basin No 9 Reservoir Report
Nearby: Frog Creek #1 Rough Draw
Last Updated: December 8, 2025
Thunder Basin No 9, located in Weston County, Wyoming, is a Federal-owned earth dam constructed in 1937 for purposes including fire protection, stock watering, and small fish pond management.
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Summary
The dam stands at a height of 21 feet and spans a length of 420 feet, with a storage capacity of 53 acre-feet and a surface area of 6 acres. It is situated on Little Frog Creek, with a drainage area of 2 square miles and a maximum discharge of 2 cubic feet per second.
Managed by the USDA Forest Service, Thunder Basin No 9 has a low hazard potential and is currently rated as not assessed for its condition. The dam features an uncontrolled spillway with a width of 50 feet and is inspected every 10 years, with the last inspection conducted in 2011. Despite its moderate risk assessment, the dam serves as a vital resource for water management and wildlife habitat in the region.
In the event of an emergency, the dam's Emergency Action Plan (EAP) status is unspecified, highlighting the need for updated safety measures and risk management protocols. With its strategic location and multiple purposes, Thunder Basin No 9 plays a crucial role in maintaining water resources and supporting various recreational and environmental activities in the area.
Year Completed |
1937 |
Dam Length |
420 |
Dam Height |
21 |
River Or Stream |
LITTLE FROG CREEK |
Primary Dam Type |
Earth |
Surface Area |
6 |
Hydraulic Height |
17 |
Drainage Area |
2 |
Nid Storage |
53 |
Structural Height |
21 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
21 |
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.
Thunder Basin No 9