Helena Valley Reservoir Report

Last Updated: December 5, 2025

Helena Valley, located in Lewis and Clark County, Montana, is home to a vital water resource infrastructure known as the Helena Valley Dam.


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Summary

Built in 1957 by the Bureau of Reclamation, this earth dam stands at 94 feet high and serves primarily for irrigation purposes in the region. With a maximum storage capacity of 10,702 acre-feet and a surface area of 531 acres, the dam plays a crucial role in managing water supply for agricultural needs in the area.

The dam, situated on Tenmile Creek TR, is operated and regulated by the Bureau of Reclamation, ensuring efficient water distribution for irrigation and other water supply purposes. Despite its high hazard potential, the dam's condition assessment is currently not available, highlighting the need for regular inspections and risk management measures. With its strategic location and significant storage capacity, Helena Valley Dam remains a key asset in maintaining water security and supporting agricultural activities in the region.

As a major water infrastructure project in the Helena Valley area, the dam's importance cannot be overstated in ensuring water availability for irrigation and other uses. With its history dating back to the mid-20th century, the dam continues to play a critical role in water management, highlighting the intersection of water resource management and climate resilience in the region.

Year Completed

1957

Dam Length

1900

Dam Height

94

River Or Stream

TENMILE CREEK TR

Primary Dam Type

Earth

Surface Area

531

Hydraulic Height

66

Drainage Area

3

Nid Storage

10702

Structural Height

94

Hazard Potential

High

Foundations

Rock

Nid Height

94
       
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.