Culmback Reservoir Report

Last Updated: December 15, 2025

Culmback is a significant dam located in Snohomish, Washington, with a primary purpose of hydroelectric power generation.


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Summary

Built in 1983, this rockfill dam stands at a height of 262 feet and has a storage capacity of 193,440 acre-feet, making it a crucial infrastructure for managing water resources in the region. The dam serves multiple purposes including flood risk reduction, recreation, and water supply, highlighting its importance in supporting the local ecosystem and community.

Managed by the Federal Energy Regulatory Commission, Culmback has a high hazard potential and a moderate risk assessment rating. Despite its age, the dam's condition assessment is not available, emphasizing the need for regular inspections and maintenance to ensure public safety and operational efficiency. With a drainage area of 68 square miles and a maximum discharge capacity of 57,132 cubic feet per second, Culmback plays a vital role in water management for the Sultan River and Skykomish River, showcasing its significance in regulating water flow and supporting various environmental activities.

As a key structure in the Seattle District, Culmback's design by R.W. Beck & Associates reflects state-of-the-art engineering for sustainable water resource management. With its strategic location and critical role in hydroelectric power generation, Culmback stands as a testament to the intersection of water resource management and climate resilience, embodying the importance of sustainable infrastructure in safeguarding our natural resources for future generations.

Year Completed

1983

Dam Length

640

Dam Height

262

River Or Stream

Sultan River, Skykomish River

Primary Dam Type

Rockfill

Surface Area

1870

Hydraulic Height

242

Drainage Area

68

Nid Storage

193440

Structural Height

262

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

262
       
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.