Issaquah Highlands Detention Pond Reservoir Report

Last Updated: December 15, 2025

The Issaquah Highlands Detention Pond in Issaquah, Washington, serves as a crucial infrastructure for flood risk reduction in the area.


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Summary

Completed in 2008, this earth dam structure stands at a hydraulic height of 22 feet and spans 600 feet in length. With a maximum storage capacity of 53 acre-feet and a normal storage capacity of 44 acre-feet, it plays a vital role in managing water levels and protecting the surrounding community from potential flooding events.

Owned and regulated by the Washington Department of Ecology, the pond is located offstream of the East Fork Issaquah Creek and covers a drainage area of 0.28 square miles. Despite its high hazard potential, the detention pond has been assessed as satisfactory in condition, with the last inspection conducted in April 2018. The facility is designed to effectively mitigate flood risks and ensure the safety of nearby residents, highlighting the importance of proactive water resource management in the face of changing climate patterns.

With its strategic location and engineering design, the Issaquah Highlands Detention Pond stands as a key component of flood risk reduction efforts in King County, Washington. As a local government-owned structure, it plays a critical role in safeguarding the community from potential inundation events and ensuring the effective management of water resources in the region. With its satisfactory condition assessment and adherence to state regulatory standards, this detention pond serves as a model for sustainable water infrastructure development in the face of climate change challenges.

Year Completed

2008

Dam Length

600

River Or Stream

Offstream - E Fork Issaquah Cr

Primary Dam Type

Earth

Hydraulic Height

22

Drainage Area

0.28

Nid Storage

53

Structural Height

22

Hazard Potential

High

Nid Height

22
       
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.