Mill Creek Storage Dam - Diversion Dam Reservoir Report
Last Updated: December 15, 2025
The Mill Creek Storage Dam - Diversion Dam, located in Walla Walla, Washington, was completed in 1942 by the US Army Corps of Engineers with the primary purpose of flood risk reduction.
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Summary
This earth dam stands at a structural height of 14 feet and is primarily made of stone. While it currently does not store water, its uncontrolled spillway allows for water management during severe weather events or to relieve pressure on the dam to maintain structural integrity.
The dam has been assessed to have a significant hazard potential and moderate risk level. To manage dam-related flood risks, the US Army Corps of Engineers implements ongoing monitoring, prioritizes risk-reducing activities, and collaborates with local emergency managers to raise awareness and develop emergency response plans. Regular maintenance and repairs are conducted to ensure the dam's proper functioning. Despite the inherent risks associated with dams and potential for flooding, the USACE's risk management measures aim to mitigate these risks and ensure public safety.
In the event of a dam-related emergency, the US Army Corps of Engineers has an emergency action plan in place, regularly updated, to guide response efforts. The dam's risk management measures focus on proactive risk reduction, community engagement, and preparedness to address the potential impacts of severe weather events or dam failures. As water resource and climate enthusiasts, understanding the importance of effective dam management and risk mitigation strategies is essential for ensuring the safety and resilience of our water infrastructure.
Year Completed |
1942 |
River Or Stream |
Mill Creek |
Primary Dam Type |
Earth |
Structural Height |
14 |
Outlet Gates |
Uncontrolled - 0 |
Hazard Potential |
Significant |
Nid Height |
14 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Mill Creek At Walla Walla
|
165cfs |
Mill Creek At Five Mile Rd Br Nr Walla Walla
|
634cfs |
Mill Creek Near Walla Walla
|
53cfs |
Walla Walla River Near Touchet
|
832cfs |
Umatilla River Above Meacham Creek
|
157cfs |
Meacham Creek At Gibbon
|
233cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Mill Creek Storage Dam - Diversion Dam