Pend Oreille Mine Ne Tailings Dam Reservoir Report

Last Updated: December 15, 2025

The Pend Oreille Mine NE Tailings Dam in Washington state, designed by Knight Piesold and completed in 2001, serves as an offstream structure along the Pend Oreille River.


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Summary

Standing at a height of 72 feet, this earth dam with rockfill core has a storage capacity of 2,900 acre-feet and covers a surface area of 3 acres. It is regulated by the Washington Department of Ecology and undergoes regular inspections, with the last one conducted in July 2019.

With a significant hazard potential but a satisfactory condition assessment, the dam is equipped to handle emergencies, although details on emergency action plans and risk assessments are currently unavailable. Its purpose primarily revolves around storing tailings, and its location in Pend Oreille County emphasizes the importance of responsible management and maintenance to ensure the safety of nearby communities and the environment. As a site of ongoing monitoring and enforcement, the Pend Oreille Mine NE Tailings Dam stands as a crucial piece of infrastructure in the region.

Water resource and climate enthusiasts can appreciate the intricate design and operational details of the Pend Oreille Mine NE Tailings Dam, recognizing its role in mitigating potential hazards and safeguarding water resources in the area. As a privately owned structure overseen by state regulatory agencies, this dam serves as a testament to the importance of effective dam management practices in maintaining the balance between human development and environmental conservation. Its proximity to the Pend Oreille River underscores the interconnectedness of water resources, infrastructure, and climate resilience, highlighting the need for continual vigilance and adherence to safety protocols to protect both the dam and the surrounding ecosystem.

Year Completed

2001

Dam Length

500

River Or Stream

Offstream, Pend Oreille R.

Primary Dam Type

Earth

Surface Area

3

Hydraulic Height

72

Drainage Area

0.42

Nid Storage

2900

Structural Height

72

Hazard Potential

Significant

Foundations

Rock, Soil

Nid Height

72
       
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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.