Duncan Dam No 1 Reservoir Report

Last Updated: December 5, 2025

Duncan Dam No 1, located in Pend Oreille, Washington, was completed in 1966 with a primary purpose of recreation.


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Summary

Owned privately, this earth dam stands at a hydraulic height of 16 feet and a structural height of 12 feet, with a length of 176 feet. It has a storage capacity of 150 acre-feet, with a normal storage level of 96 acre-feet. The dam is situated on Tr-Pend Oreille River and is under the jurisdiction of the Washington Dept of Ecology.

With a low hazard potential and a condition assessment of "Not Rated," Duncan Dam No 1 is regulated and inspected by state authorities, ensuring its safety and continued operation. While it does not have a spillway or outlet gates, the dam serves the community for irrigation and recreational purposes. Although last inspected in 2000, the dam's emergency action plan status and risk assessment details are currently unknown. Despite these gaps in information, Duncan Dam No 1 remains a vital resource for water management and outdoor activities in the region.

Year Completed

1966

Dam Length

176

River Or Stream

Tr-Pend Oreille River

Primary Dam Type

Earth

Surface Area

96

Hydraulic Height

16

Drainage Area

0.5

Nid Storage

150

Structural Height

12

Hazard Potential

Low

Foundations

Soil

Nid Height

16
       
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.