Howard A. Hanson Dam Reservoir Report

Last Updated: December 15, 2025

Howard A.


°F

°F

mph

Wind

%

Humidity

Summary

Hanson Dam, located in Auburn, Washington, is a rockfill dam primarily designed for flood risk reduction along the Green River. Completed in 1962 by the US Army Corps of Engineers (USACE), the dam has a hydraulic height of 220 feet and a structural height of 235 feet, with a maximum storage capacity of 136,700 acre-feet. While the dam plays a crucial role in reducing flood risks, extreme rainfall events could still necessitate controlled releases through the outlet tunnel or spillway to prevent overtopping and potential failure.

USACE has implemented numerous risk management measures to ensure the dam's safety and reduce risks to life safety and property. This includes regular inspections, monitoring instrumentation, and maintenance activities to address any potential concerns. The agency also collaborates with local emergency managers to update the Emergency Action Plan annually, conducts emergency exercises, and hosts stakeholder meetings to keep the community informed. Despite the low likelihood of dam failure scenarios, USACE remains committed to safeguarding the dam and mitigating potential risks to downstream communities in Auburn, Kent, and beyond.

Overall, Howard A. Hanson Dam remains a vital infrastructure for flood risk reduction in the region, with USACE's ongoing efforts to maintain the dam's integrity and ensure its resilience in the face of extreme weather events. Through continuous monitoring, maintenance, and collaboration with local authorities, the dam serves as a critical asset in protecting communities from potential flooding disasters.

Year Completed

1962

Dam Length

500

River Or Stream

GREEN

Primary Dam Type

Rockfill

Surface Area

20000

Hydraulic Height

220

Drainage Area

221

Nid Storage

136700

Structural Height

235

Hazard Potential

High

Nid Height

235
       
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.