Big Boy Reservoir Report
Nearby: Pat Phil No. 2
Last Updated: December 5, 2025
Big Boy is a privately owned earth dam located in Johnson County, Wyoming, near the city of Arvada.
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Summary
Completed in 1969, the dam stands at a height of 33 feet and serves multiple purposes including fire protection, stock watering, and as a small fish pond. With a storage capacity of 55 acre-feet, the dam covers a surface area of 4 acres and has a drainage area of 2.4 square miles.
Despite its low hazard potential, the dam's condition assessment is rated as poor, indicating a need for maintenance and repairs. The last inspection in June 2021 highlighted this concern, with a moderate risk assessment score of 3. While the dam has an uncontrolled spillway with a width of 40 feet, it lacks outlet gates for controlled water release. The primary source agency for Big Boy is the Wyoming State Engineer's Office, which regulates, inspects, and enforces safety standards for the dam.
Water resource and climate enthusiasts will find Big Boy to be an intriguing structure due to its multiple uses and the challenges it faces in terms of maintenance and risk management. The dam's location along Caple Drive and Triple Crossing Drive provides important water resources for the surrounding area, emphasizing the importance of ensuring its safety and stability. As discussions around water management and climate adaptation continue, the condition of dams like Big Boy will be crucial in safeguarding water resources for future generations.
Year Completed |
1969 |
Dam Length |
350 |
Dam Height |
33 |
River Or Stream |
CAPLE DR, TR DBLE. CROSSING DR |
Primary Dam Type |
Earth |
Surface Area |
4 |
Hydraulic Height |
28 |
Drainage Area |
2.4 |
Nid Storage |
55 |
Structural Height |
33 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
33 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Piney Creek At Kearny
|
113cfs |
Clear Creek Near Buffalo
|
12cfs |
Powder River At Arvada
|
156cfs |
Rock Creek Near Buffalo
|
70cfs |
Wild Horse Creek Near Arvada
|
0cfs |
South Piney Creek At Willow Park
|
0cfs |
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.
Big Boy