Stillwater Reservoir Report

Last Updated: December 5, 2025

Stillwater, located in Franktown, Colorado, is a privately owned dam on Antelope Creek with a primary purpose of recreation.


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Summary

Built in 1999 by Woodward Clyde, this earth dam stands at a height of 27 feet and stretches 1100 feet in length, creating a storage capacity of 326 acre-feet and serving as a popular spot for outdoor activities. The dam boasts a spillway width of 8 feet and a low hazard potential, with a fair condition assessment as of 2013.

Despite its modest size and purpose, Stillwater plays a key role in the local water resource management, offering a surface area of 22 acres for recreational use and a drainage area of 1 square mile. With a maximum discharge capacity of 105 cubic feet per second, the dam provides a valuable water source for the surrounding community while also enhancing the natural landscape. The dam's inspection frequency of 6 years ensures regular maintenance and upkeep to uphold its structural integrity and safeguard against potential risks, contributing to the overall sustainability and resilience of the region's water infrastructure.

Year Completed

1999

Dam Length

1100

Dam Height

27

River Or Stream

ANTELOPE CREEK

Primary Dam Type

Earth

Surface Area

22

Hydraulic Height

27

Drainage Area

1

Nid Storage

326

Structural Height

27

Outlet Gates

Slide (sluice gate) - 1

Hazard Potential

Low

Foundations

Rock, Soil

Nid Height

27
       
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.