Granite Springs Reservoir Report

Last Updated: December 5, 2025

Granite Springs, also known as Cheyenne #2, is a historic masonry dam located in Laramie, Wyoming, serving as a crucial water supply source for the city of Cheyenne.


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Summary

Completed in 1904, this architectural marvel stands at a height of 90 feet and has a storage capacity of 5,780 acre-feet. Situated on Middle Crow Creek, the dam's primary purpose is to ensure reliable water access for the region, with a drainage area of 28.4 square miles and a maximum discharge rate of 29,800 cubic feet per second.

Despite its age, Granite Springs has been well-maintained, with regular inspections and a fair condition assessment as of June 2017. The dam features an uncontrolled spillway, two other controlled outlet gates, and a high hazard potential due to its critical role in water supply management. With a moderate risk assessment rating, ongoing risk management measures are in place to mitigate any potential hazards and ensure the safety and functionality of the structure. As a key infrastructure asset in the region, Granite Springs plays a vital role in water resource management and climate resilience efforts in Wyoming.

Year Completed

1904

Dam Length

423

Dam Height

90

River Or Stream

MIDDLE CROW CREEK

Primary Dam Type

Masonry

Surface Area

190

Hydraulic Height

87

Drainage Area

28.4

Nid Storage

5780

Structural Height

90

Outlet Gates

Other Controlled - 2

Hazard Potential

High

Foundations

Soil

Nid Height

90
       
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.