Mill Pond Stormwater Detention Dam Reservoir Report

Last Updated: December 15, 2025

The Mill Pond Stormwater Detention Dam in Auburn, Washington, stands as a crucial infrastructure designed for flood risk reduction.


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Summary

Completed in 1994, this earth dam with a stone core serves its primary purpose of safeguarding the local community from potential flooding events. With a hydraulic height of 10 feet and the capacity to store up to 16 acre-feet of water, this offstream structure plays a significant role in managing stormwater runoff and protecting downstream areas.

Located in King County, Washington, the Mill Pond Dam is regulated by the Washington Department of Ecology and undergoes regular inspections to ensure its structural integrity. Despite being assessed as in fair condition in 2015, the dam's hazard potential is classified as high, highlighting the importance of ongoing maintenance and monitoring efforts. The dam's emergency action plan was last revised in 2017, underscoring the commitment to preparedness and risk management in the face of potential emergencies.

As a vital component of the local flood control system, the Mill Pond Stormwater Detention Dam plays a critical role in mitigating flood risks in the region. With its strategic location and design, this dam stands as a testament to effective water resource management and climate resilience efforts in the state of Washington. By fulfilling its designated purpose and adhering to regulatory standards, the Mill Pond Dam serves as a valuable asset in safeguarding the community and preserving the surrounding environment for generations to come.

Year Completed

1994

River Or Stream

Offstream

Primary Dam Type

Earth

Hydraulic Height

10

Drainage Area

0.8

Nid Storage

16

Structural Height

10

Hazard Potential

High

Foundations

Soil

Nid Height

10
       
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.