Chaplain Lake North Dam Reservoir Report

Last Updated: December 15, 2025

Chaplain Lake North Dam, located in Monroe, Washington, serves as a vital water supply structure for the region.


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Summary

Built in 1940, this earth dam stands at a hydraulic height of 35 feet, with a structural height of 15 feet and a length of 650 feet. The dam has a maximum storage capacity of 18,200 acre-feet and covers a surface area of 450 acres, drawing water from the Tr-Woods Creek for its operations.

Maintained and regulated by the Washington Department of Ecology, Chaplain Lake North Dam is inspected every five years to ensure its structural integrity. With a high hazard potential but a satisfactory condition assessment as of July 2019, the dam plays a crucial role in managing water resources in Snohomish County. Despite its age, the dam continues to meet the region's water supply needs and remains a key component in mitigating the impacts of climate change on local water systems.

As climate change poses increasing challenges to water resources, Chaplain Lake North Dam stands as a testament to the importance of sustainable water management infrastructure. With its role in supplying water to the region and its continued operation under regulatory oversight, the dam serves as a critical asset in ensuring water security for the community. As discussions around climate adaptation and resilience grow, Chaplain Lake North Dam's significance in safeguarding water resources in Snohomish County remains paramount.

Year Completed

1940

Dam Length

650

River Or Stream

Tr-Woods Creek

Primary Dam Type

Earth

Surface Area

450

Hydraulic Height

35

Drainage Area

2.6

Nid Storage

18200

Structural Height

15

Hazard Potential

High

Foundations

Soil

Nid Height

35
       
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.