Mill Pond Reservoir Report

Last Updated: December 15, 2025

Mill Pond, located in Metaline Falls, Washington, is a gravity dam completed in 1922 for hydroelectric and recreational purposes.


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Summary

Standing at 65 feet tall with a hydraulic height of 57 feet, the dam holds a storage capacity of 1430 acre-feet and covers a surface area of 65 acres. The dam, situated on Sullivan Creek and the Pend Oreille River, has a maximum discharge of 4000 cubic feet per second and features an uncontrolled spillway with a width of 84 feet.

Owned and operated by a public utility, Mill Pond is regulated by the Federal Energy Regulatory Commission (FERC) and falls under the jurisdiction of the Seattle District. With a hazard potential classified as high and a moderate risk assessment rating, the dam is subject to regular inspections by FERC to ensure its structural integrity. Despite its age, the condition assessment of Mill Pond is currently listed as "Not Available," highlighting the need for ongoing monitoring and maintenance to mitigate any potential risks associated with the dam.

For water resource and climate enthusiasts, Mill Pond serves as a fascinating example of early 20th-century engineering designed to harness the power of flowing water for renewable energy production. The dam not only provides electricity but also offers recreational opportunities for the local community. As climate change continues to impact water resources, understanding the role of dams like Mill Pond in managing water flow and storage becomes increasingly important for sustainable water management practices in the region.

Year Completed

1922

Dam Length

130

Dam Height

55

River Or Stream

Sullivan Creek, Pend Oreille R

Primary Dam Type

Gravity

Surface Area

65

Hydraulic Height

57

Drainage Area

125

Nid Storage

1430

Structural Height

65

Hazard Potential

High

Nid Height

65
       
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.