Quadrant Lake No 1 Reservoir Report

Last Updated: December 15, 2025

Quadrant Lake No 1, located in Federal Way, Washington, is a privately owned gravity dam that was completed in 1994 for flood risk reduction purposes.


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Summary

With a structural height of 8 feet and a length of 180 feet, the dam has a maximum storage capacity of 113 acre-feet and a normal storage of 57 acre-feet. It serves a drainage area of 0.73 square miles and can discharge up to 480 cubic feet per second.

Managed by the Washington Dept of Ecology, Quadrant Lake No 1 is state regulated and inspected to ensure its safety and compliance with regulatory standards. With a low hazard potential and a condition assessment of "Not Rated," the dam has not undergone recent inspections or risk assessments. While emergency action plans and inundation maps are not currently prepared, the dam's performance and risk management measures are not detailed in the available data.

Overall, Quadrant Lake No 1 plays a crucial role in flood risk reduction in the area, highlighting the importance of effective management and monitoring of water resources to mitigate potential hazards and ensure public safety. For water resource and climate enthusiasts, this dam serves as a fascinating case study in dam engineering and regulatory oversight in the state of Washington.

Year Completed

1994

Dam Length

180

River Or Stream

Offstream

Primary Dam Type

Gravity

Surface Area

57

Hydraulic Height

8

Drainage Area

0.73

Nid Storage

113

Structural Height

8

Hazard Potential

Low

Foundations

Soil

Nid Height

8
       
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.