Mill Pond Dike Reservoir Report

Last Updated: December 15, 2025

Mill Pond Dike, located in Metaline Falls, Washington, serves as a crucial infrastructure for hydroelectric power generation and recreational activities.


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Summary

Built in 1922, this earth dam stands at a height of 8 feet and stretches over 850 feet in length, with a storage capacity of 1,430 acre-feet. Sullivan Creek is the primary water source for this dam, which has a drainage area of 125 square miles and a maximum discharge of 4,000 cubic feet per second.

Managed by the Federal Energy Regulatory Commission, Mill Pond Dike is considered to have a high hazard potential due to its location and structure. Despite its age, the dam has not undergone recent condition assessments, but emergency action plans have been prepared and revised to ensure public safety in the event of a breach. The surrounding area spans 65 acres and offers recreational opportunities for visitors, making it a valuable asset for both water resource management and community enjoyment.

With a risk assessment rating of 2, indicating a high risk level, maintaining the integrity of Mill Pond Dike is paramount to prevent potential hazards and ensure the safety of downstream communities. Regular inspections and risk management measures are essential to mitigate any potential threats and uphold the structural stability of this vital infrastructure. As climate change continues to impact water resources, sustainable management practices will be crucial in safeguarding Mill Pond Dike and its surrounding environment for future generations.

Year Completed

1922

Dam Length

850

Dam Height

8

River Or Stream

Sullivan Creek

Primary Dam Type

Earth

Surface Area

65

Hydraulic Height

3

Drainage Area

125

Nid Storage

1430

Structural Height

8

Hazard Potential

High

Nid Height

8
       
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.