Klahanie Stormwater Detention Dam No 13 Reservoir Report

Last Updated: December 15, 2025

Klahanie Stormwater Detention Dam No 13, located in Issaquah, Washington, is a vital structure owned by the local government to manage flood risk reduction in the area.


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Summary

Completed in 1989, this earth dam stands at a hydraulic height of 10 feet and a structural height of 8 feet, with a length of 860 feet and a storage capacity of 56 acre-feet. Situated along the Tr-Issaquah Creek, this dam plays a crucial role in protecting the surrounding community from potential flooding events.

With a fair condition assessment and a high hazard potential, Klahanie Stormwater Detention Dam No 13 is regularly inspected by the Washington Dept of Ecology to ensure its effectiveness in flood risk reduction. The dam covers a drainage area of 0.16 square miles and has a normal storage capacity of 35 acre-feet, serving as a key infrastructure for managing stormwater in the region. Despite its age, the dam continues to play a critical role in safeguarding the local environment and residents from the impacts of extreme weather events.

As part of the flood risk reduction strategy in King County, Washington, Klahanie Stormwater Detention Dam No 13 is a significant component of the overall water resource management plan. With a focus on maintaining public safety and protecting against potential inundation, this dam stands as a testament to the proactive measures taken by local authorities to mitigate the effects of climate change on the surrounding community.

Year Completed

1989

Dam Length

860

River Or Stream

Tr-Issaquah Creek

Primary Dam Type

Earth

Surface Area

11.1

Hydraulic Height

10

Drainage Area

0.16

Nid Storage

56

Structural Height

8

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.