Lost Lake Reservoir Report

Last Updated: December 5, 2025

Lost Lake, located in Mesa, Colorado, is a privately owned Earth dam built in 1922 for irrigation purposes.


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Summary

The dam stands at a height of 12 feet with a hydraulic height of 11 feet and a length of 280 feet, providing a storage capacity of 126 acre-feet. The reservoir covers an area of 26 acres and is fed by the Bull Creek-TR stream, with a maximum discharge capacity of 44 cubic feet per second.

Despite its age, Lost Lake's hazard potential is classified as low, with a fair condition assessment as of 2010. The dam features an uncontrolled spillway and one slide gate outlet, with inspection and maintenance carried out by the Colorado Division of Water Resources. The surrounding area is at a moderate risk level, requiring ongoing risk management measures to ensure the safety and stability of the structure.

Lost Lake is a historic dam that continues to serve its intended purpose of irrigation while maintaining a relatively low hazard potential. With its stone core and rock-soil foundations, the dam stands as a testament to early 20th-century engineering. As water resource and climate enthusiasts, understanding and preserving the infrastructure of Lost Lake is crucial for maintaining water supply and mitigating risks in the face of changing environmental conditions.

Year Completed

1922

Dam Length

280

Dam Height

12

River Or Stream

BULL CREEK-TR

Primary Dam Type

Earth

Surface Area

26

Hydraulic Height

11

Nid Storage

126

Structural Height

12

Outlet Gates

Slide (sluice gate) - 1

Hazard Potential

Low

Foundations

Rock, Soil

Nid Height

12
       
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.