Seaway Center Stormwater Detention Dam Reservoir Report
Last Updated: December 15, 2025
The Seaway Center Stormwater Detention Dam, located in Mukilteo, Washington, is a vital structure designed for flood risk reduction along the Tr-Powder Mill Gulch.
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Summary
Owned by the local government and regulated by the Washington Department of Ecology, this earth dam stands at a hydraulic height of 39 feet, with a structural height of 38 feet, offering a maximum storage capacity of 27 acre-feet. Completed in 1989, this dam plays a crucial role in managing stormwater runoff and protecting the surrounding area from potential flooding events.
With a significant hazard potential and a satisfactory condition assessment, the Seaway Center Stormwater Detention Dam serves as a key component of the local water resource infrastructure. The dam covers a surface area of 14 acres and drains an area of 0.08 square miles, with a maximum discharge capacity of 90 cubic feet per second. Despite its age, the dam's last inspection in June 2016 deemed it to be in good working order, ensuring its effectiveness in safeguarding the community against flood-related risks.
As climate change continues to impact weather patterns and increase the frequency of extreme precipitation events, structures like the Seaway Center Stormwater Detention Dam play a crucial role in managing water resources and mitigating flood risks. With its strategic location and reliable performance history, this dam stands as a testament to effective flood risk reduction efforts in the Snohomish County region of Washington.
Year Completed |
1989 |
River Or Stream |
Tr-Powder Mill Gulch |
Primary Dam Type |
Earth |
Surface Area |
14 |
Hydraulic Height |
39 |
Drainage Area |
0.08 |
Nid Storage |
27 |
Structural Height |
38 |
Hazard Potential |
Significant |
Foundations |
Soil |
Nid Height |
39 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Seaway Center Stormwater Detention Dam
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