Western Hillside Reservoir Reservoir Report

Last Updated: December 4, 2025

The Western Hillside Reservoir, also known as Trappers Reservoir, is a privately owned water storage facility located in Avon, Colorado.


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Summary

Completed in 1997, this earth dam stands at a height of 46 feet and has a storage capacity of 154 acre-feet. Situated along the Bachelor Gulch-OS river, the reservoir serves as a critical water source for the surrounding area, with a normal storage level of 124 acre-feet and a maximum discharge capacity of 224 cubic feet per second.

Managed by the Colorado Department of Water Resources, the Western Hillside Reservoir is subject to state regulations, inspections, and enforcement measures to ensure its structural integrity and safety. The dam's spillway, of uncontrolled type, is 16 feet wide and designed to handle high hazard potential. With a satisfactory condition assessment as of August 2020, the reservoir poses a moderate risk level, prompting the need for ongoing risk management measures and emergency preparedness.

Despite its relatively small surface area of 5 acres, the Western Hillside Reservoir plays a crucial role in water resource management for the Eagle County region. With its strategic location in the hillside terrain, the reservoir serves as a vital storage and distribution point in the local water infrastructure system. Enthusiasts of water resources and climate sustainability will find the design and operational details of this reservoir fascinating, highlighting the intricate balance between water supply, dam safety, and environmental stewardship in the Western United States.

Year Completed

1997

Dam Length

1300

Dam Height

46

River Or Stream

BACHELOR GULCH-OS

Primary Dam Type

Earth

Surface Area

5

Hydraulic Height

42

Nid Storage

154

Structural Height

46

Outlet Gates

Slide (sluice gate) - 1, Valve - 1

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

46
       
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.