Mill Creek Lake Reservoir Report

Last Updated: January 11, 2026

Mill Creek Lake in Lemhi, Idaho, is a privately owned water resource with a state-regulated dam that was completed in 1928.


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Summary

The dam, primarily made of earth and stone, stands at a height of 19.3 feet and has a hydraulic height of 15.8 feet, creating a storage capacity of 210 acre-feet. With a controlled spillway and low hazard potential, the dam is deemed to be in fair condition as of its last inspection in 2016.

This scenic lake covers a surface area of 29 acres and is fed by Mill Creek and the Lemhi River. Its primary purpose is classified as "Other," and it serves as a vital water source for the surrounding area. Despite its fair condition assessment, the risk assessment for Mill Creek Lake is rated as very high (1), indicating a need for continued monitoring and risk management measures to ensure the safety and sustainability of this important water resource in Idaho.

Surrounded by the natural beauty of Lemhi County and situated within the Walla Walla District, Mill Creek Lake offers a peaceful retreat for water resource and climate enthusiasts. With its historic dam structure, ample storage capacity, and picturesque setting, this lake is not only a valuable resource for the community but also a captivating destination for those who appreciate the intersection of water management and environmental stewardship.

Year Completed

1928

Dam Length

725

Dam Height

19.3

River Or Stream

MILL CREEK LEMHI RIVER

Surface Area

29

Hydraulic Height

15.8

Drainage Area

0.7

Nid Storage

210

Hazard Potential

Low

Foundations

Rock, Soil

Nid Height

19
       
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.