Peterson Lake Reservoir Report

Last Updated: December 5, 2025

Peterson Lake in Larimer, Colorado, is a gravity dam completed in 1973 primarily for water supply purposes, serving both irrigation and domestic water needs in the area.


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Summary

With a height of 78 feet and a storage capacity of 1409 acre-feet, the dam stands as a crucial piece of infrastructure in the Cache La Poudre River watershed. Its high hazard potential is balanced by a satisfactory condition assessment, ensuring its reliability in providing water to the surrounding community.

Managed by the local government and regulated by the Colorado Division of Water Resources, Peterson Lake's spillway, with a width of 425 feet, helps control water flow during periods of high discharge. The dam's rock foundation and multi-arch core types contribute to its structural integrity, while its uncontrolled spillway type ensures effective water release when needed. Despite its moderate risk assessment, the dam's last inspection in July 2020 deemed it to be in satisfactory condition, highlighting its importance in water management and supply in the region.

Located in Fort Collins and under the jurisdiction of the Sacramento District of the US Army Corps of Engineers, Peterson Lake Dam serves as a vital resource for water storage and supply in the region. With a surface area of 55 acres and a drainage area of 2 square miles, the dam plays a crucial role in managing water resources in a sustainable and effective manner. Its history of successful operation and maintenance, coupled with its strategic location in the Cache La Poudre River watershed, underscores the importance of Peterson Lake in ensuring reliable water access for agricultural and urban needs in Larimer County, Colorado.

Year Completed

1973

Dam Length

231

Dam Height

38

River Or Stream

CACHE LA POUDRE RIVER-TR

Primary Dam Type

Gravity

Surface Area

55

Hydraulic Height

38

Drainage Area

2

Nid Storage

1409

Structural Height

78

Hazard Potential

High

Foundations

Rock

Nid Height

78
       
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.