Lone Cone Reservoir Report

Last Updated: December 9, 2025

Lone Cone is a private irrigation dam located in San Miguel, Colorado, along the Goshorn Creek.


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Summary

Built in 1912, this earth dam stands at a height of 25 feet and has a hydraulic height of 27 feet. With a storage capacity of 1840 acre-feet, it serves the primary purpose of irrigation, supporting the agricultural needs of the surrounding area. The dam has a fair condition assessment and is classified as having a high hazard potential, emphasizing the importance of regular inspections and risk management measures.

Despite its age, Lone Cone continues to play a crucial role in water resource management in the region. The dam has a maximum discharge capacity of 3450 cubic feet per second and covers a surface area of 177 acres. While it does not have a spillway, it is equipped with slide and uncontrolled outlet gates for water release. The dam's condition is closely monitored, with the last inspection conducted in October 2020, highlighting the commitment to ensuring the safety and functionality of this vital water infrastructure.

With its historical significance and ongoing contribution to irrigation practices, Lone Cone stands as a testament to the importance of sustainable water resource management in the face of changing climate patterns. As a regulated and permitted structure, it exemplifies the collaborative efforts between private owners and state agencies to ensure the efficient and safe operation of water infrastructure. As water enthusiasts and climate advocates, recognizing the role of dams like Lone Cone in maintaining water security and agricultural sustainability is essential for addressing the challenges posed by a changing climate.

Year Completed

1912

Dam Length

2900

Dam Height

25

River Or Stream

GOSHORN CREEK

Primary Dam Type

Earth

Surface Area

177

Hydraulic Height

27

Drainage Area

1

Nid Storage

1840

Structural Height

27

Outlet Gates

Slide (sluice gate), Uncontrolled

Hazard Potential

High

Foundations

Rock

Nid Height

27
       
Seasonal Comparison

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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.