Leonard Thomas Reservoir Reservoir Report

Last Updated: December 4, 2025

Leonard Thomas Reservoir, also known as Aspen, is a crucial water supply source located in Pitkin, Colorado.


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Summary

Built in 1964, this local government-owned reservoir serves the primary purpose of water supply, with a maximum storage capacity of 13 acre-feet. The dam, constructed with earth and stone core types, stands at a height of 19 feet and a length of 280 feet, providing a structural height of 21 feet.

With a significant hazard potential and a satisfactory condition assessment, Leonard Thomas Reservoir is subject to regular inspections and maintenance to ensure its safety and functionality. The reservoir's spillway type is uncontrolled, with a spillway width of 13 feet. In case of emergencies, the reservoir is equipped with two vertical lift outlet gates to manage water discharge. Overall, Leonard Thomas Reservoir plays a critical role in water resource management in the region, contributing to the local water supply infrastructure.

Situated along Castle Creek-OS, Leonard Thomas Reservoir is regulated by the Colorado Department of Water Resources (DWR) and falls under state jurisdiction for permitting, inspection, and enforcement. The reservoir has a normal storage capacity of 10 acre-feet and a maximum discharge capacity of 207 cubic feet per second. The risk assessment for Leonard Thomas Reservoir is moderate, with measures in place to manage potential risks and ensure the safety of the surrounding community. As a key water resource in the area, Leonard Thomas Reservoir showcases the importance of sustainable water management practices in the face of climate change and increasing water demands.

Years Modified

2011 - Hydraulic

Year Completed

1964

Dam Length

280

Dam Height

19

River Or Stream

CASTLE CREEK-OS

Primary Dam Type

Earth

Surface Area

1

Hydraulic Height

18

Nid Storage

13

Structural Height

21

Outlet Gates

Vertical Lift - 2

Hazard Potential

Significant

Foundations

Rock, Soil

Nid Height

21
       
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.