Lost Reservoir Report
Nearby: Big Pike Dam Alkali Dam
Last Updated: December 13, 2025
Lost is a Federal-owned dam located in Natrona, Wyoming, specifically in the city of SUSSEX.
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Summary
Built in 1966, Lost serves multiple purposes including fire protection, stock, small fish pond, and flood risk reduction along the Lost Creek. The earth dam stands at a height of 29 feet with a hydraulic height of 24 feet and a structural height of 29 feet, storing a maximum of 40 acre-feet with a normal storage capacity of 23 acre-feet.
With a low hazard potential and fair condition assessment, Lost has a spillway width of 100 feet and a maximum discharge of 372 cubic feet per second. The dam, primarily made of earth and stone core, covers a surface area of 3 acres with a drainage area of 0.7 square miles. Despite its moderate risk assessment rating, Lost remains a vital structure for water resource management and climate adaptation efforts in the region, requiring regular inspections every five years to ensure its continued safety and reliability.
Year Completed |
1966 |
Dam Length |
388 |
Dam Height |
29 |
River Or Stream |
LOST CREEK |
Primary Dam Type |
Earth |
Surface Area |
3 |
Hydraulic Height |
24 |
Drainage Area |
0.7 |
Nid Storage |
40 |
Structural Height |
29 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
29 |
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.
Lost