Fossil Dam Reservoir Report

Last Updated: December 15, 2025

Fossil Dam, located in Natrona, Wyoming, serves as a vital debris control structure along the Fossil Draw river.


°F

°F

mph

Wind

%

Humidity

Summary

Owned and regulated by the Bureau of Land Management, this gravity dam stands at a height of 35 feet and was completed in 1966. With a primary purpose of debris control, Fossil Dam has a normal storage capacity of 19 acre-feet and a maximum discharge of 230 cubic feet per second.

Despite being classified as having a low hazard potential, Fossil Dam's condition assessment is marked as unsatisfactory. The dam has a moderate risk rating and undergoes inspections every five years, with the last inspection conducted in 2017. With an uncontrolled spillway type and no outlet gates, the dam presents a moderate risk level that necessitates ongoing risk management measures to ensure public safety and environmental protection.

Water resource and climate enthusiasts will find Fossil Dam's design and functionality intriguing, as it plays a critical role in managing debris and maintaining water flow along the Fossil Draw river. The dam's location within a federal jurisdiction underscores the importance of proper regulation and inspection to address any potential risks associated with its operation. As a key component in the region's water infrastructure, Fossil Dam continues to be a focal point for monitoring and maintaining its structural integrity for long-term sustainability.

Year Completed

1966

Dam Length

300

River Or Stream

FOSSIL DRAW

Primary Dam Type

Gravity

Surface Area

6.1

Hydraulic Height

28

Drainage Area

1.91

Nid Storage

33

Structural Height

35

Outlet Gates

None

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

35
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.