Spinney Mountain Reservoir Report

Last Updated: December 5, 2025

Located in Park County, Colorado, Spinney Mountain is a vital water resource managed by the local government for water supply purposes.


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Summary

This earth dam, completed in 1982, stands at a height of 90 feet and has a storage capacity of 83,300 acre-feet. Situated along the South Platte River, this reservoir covers a surface area of 2,450 acres and serves as a popular recreational spot while also supporting water supply needs in the region.

With a maximum discharge capacity of 104,000 cubic feet per second and a spillway width of 540 feet, Spinney Mountain Dam plays a crucial role in managing water flow and preventing flooding. Despite being classified as having a high hazard potential, the dam is in satisfactory condition and undergoes regular inspections to ensure its safety and functionality. Additionally, the dam's risk assessment indicates a moderate risk level, highlighting the importance of ongoing monitoring and risk management measures.

With its picturesque location and significant role in water management, Spinney Mountain Dam serves as a key infrastructure asset in Colorado. Climate and water resource enthusiasts can appreciate the engineering feat of this earth dam, which not only provides essential water supply but also offers opportunities for outdoor recreation along the scenic South Platte River. As a regulated and inspected structure, Spinney Mountain Dam exemplifies the careful attention given to managing water resources in the region to meet both human and environmental needs.

Year Completed

1982

Dam Length

4125

Dam Height

90

River Or Stream

SOUTH PLATTE RIVER

Primary Dam Type

Earth

Surface Area

2450

Hydraulic Height

67

Drainage Area

772

Nid Storage

83300

Structural Height

100

Hazard Potential

High

Nid Height

100
       
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.