Left Hand Valley Reservoir Report

Last Updated: December 4, 2025

Located in Boulder, Colorado, the Left Hand Valley dam, designed by Damon Runyan, stands as a critical infrastructure for irrigation purposes along Dry Creek.


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Summary

Completed in 1952, this private-owned Earth type dam boasts a height of 54 feet and a hydraulic height of 45 feet, with a storage capacity of 2814 acre-feet. Its spillway, with a width of 192 feet, serves as an uncontrolled outlet for excess water to prevent overflow.

With a high hazard potential and a satisfactory condition assessment, the Left Hand Valley dam is under state regulation and inspection by the Colorado Division of Water Resources. Despite its age, the dam continues to meet safety guidelines and poses a moderate risk (3) according to the latest risk assessment. The dam's emergency action plan was last revised in 2003, and it remains a crucial structure for water resource management and climate resilience in the region, serving as a lifeline for agricultural irrigation in the area.

Year Completed

1952

Dam Length

1035

Dam Height

54

River Or Stream

DRY CREEK

Primary Dam Type

Earth

Surface Area

113

Hydraulic Height

45

Drainage Area

3

Nid Storage

2814

Structural Height

68

Hazard Potential

High

Nid Height

68
       
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.