Button Rock Reservoir Report

Last Updated: December 5, 2025

Button Rock, located in Boulder County, Colorado, is a vital water supply dam situated on the North St.


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Summary

Vrain Creek. Built in 1969 by McCall-Ellingson, this earth dam stands at a height of 214 feet and has a storage capacity of 20,400 acre-feet, serving as a crucial resource for the city of Lyons. With a maximum discharge of 29,000 cubic feet per second and a spillway width of 110 feet, Button Rock plays a key role in regulating water flow and ensuring water security for the region.

Despite its age, Button Rock maintains a satisfactory condition assessment and is inspected regularly to ensure its safety and functionality. With a high hazard potential due to its location and purpose, the dam is subject to state regulation, permitting, inspection, and enforcement by the Colorado Division of Water Resources. The risk assessment for Button Rock is moderate, indicating a need for ongoing risk management measures to protect the surrounding area from potential hazards. Overall, Button Rock stands as a testament to the importance of water resource management and climate resilience in the face of changing environmental conditions.

Year Completed

1969

Dam Length

925

Dam Height

210

River Or Stream

NORTH ST. VRAIN CREEK

Primary Dam Type

Earth

Surface Area

222

Hydraulic Height

210

Drainage Area

99

Nid Storage

20400

Structural Height

214

Hazard Potential

High

Nid Height

214
       
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.