Humphreys - Spillway Dam Reservoir Report

Last Updated: December 5, 2025

Humphreys - Spillway Dam, also known as Lake Humphreys, is a private-owned structure located in Mineral County, Colorado.


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Summary

Completed in 1926, this concrete gravity dam stands at a height of 26 feet and spans 148 feet in length, with a multi-arch core foundation on rock. Its primary purpose is for fish and wildlife conservation, with additional recreational benefits. The dam has a storage capacity of 1,062 acre-feet and a normal storage level of 842 acre-feet, covering a surface area of 44 acres.

Situated on Goose Creek in South Fork, Colorado, Humphreys - Spillway Dam is regulated and inspected by the Colorado Division of Water Resources. The dam features an uncontrolled spillway with a width of 70 feet, allowing for a maximum discharge rate of 3,225 cubic feet per second. Despite its high hazard potential, the dam's condition is assessed as satisfactory as of the last inspection in July 2020. While there have been no modifications in recent years, the risk assessment for the dam is moderate, highlighting the importance of ongoing risk management measures to ensure its safety and functionality for the surrounding area.

Year Completed

1926

Dam Length

148

Dam Height

26

River Or Stream

GOOSE CREEK

Primary Dam Type

Concrete

Surface Area

44

Hydraulic Height

26

Drainage Area

53

Nid Storage

1062

Structural Height

34

Hazard Potential

High

Foundations

Rock

Nid Height

34
       
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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.