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