Centralia Coal Mine Pond 46a Dam Reservoir Report
Last Updated: December 15, 2025
Centralia Coal Mine Pond 46a Dam in Washington state is a vital structure for flood risk reduction, completed in 2004 with a primary purpose to protect the surrounding area from potential inundation.
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Summary
This earth dam stands at a hydraulic height of 16 feet and has a structural height of 13 feet, effectively managing water levels in the nearby Mitchell Creek. With a storage capacity of 48 acre-feet and a maximum discharge rate of 621 cubic feet per second, this dam plays a crucial role in safeguarding the local community against flooding events.
Located in Lewis County, Washington, the Centralia Coal Mine Pond 46a Dam covers a surface area of 3.1 acres and serves a drainage area of 0.71 square miles. Despite its significant hazard potential, the dam has been assessed as satisfactory in condition, last inspected in August 2020 with an inspection frequency of every 5 years. Managed by the Washington Department of Ecology, this dam is subject to state regulation, enforcement, and inspection, ensuring its operational integrity and safety for the surrounding environment and residents. With a designer name of EES, this dam exemplifies the collaborative effort between public utilities and regulatory agencies to mitigate flood risks and protect water resources in the region.
In the event of an emergency, the Centralia Coal Mine Pond 46a Dam is equipped with emergency action plans (EAP) to guide response procedures. The last EAP revision was in March 2022, indicating preparedness for potential incidents. While no specific risk assessment or management measures are outlined in the available data, the dam's satisfactory condition assessment and regular inspections contribute to its overall resilience and effectiveness in flood risk reduction. As a significant infrastructure in the Seattle District, this dam exemplifies the intersection of water resource management, climate resilience, and public safety in addressing the challenges of natural disasters and water management in the Pacific Northwest.
Year Completed |
2004 |
Dam Length |
100 |
River Or Stream |
Unnamed Tr - Mitchell Creek |
Primary Dam Type |
Earth |
Surface Area |
3.1 |
Hydraulic Height |
16 |
Drainage Area |
0.71 |
Nid Storage |
48 |
Structural Height |
13 |
Hazard Potential |
Significant |
Foundations |
Soil |
Nid Height |
16 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
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.
Centralia Coal Mine Pond 46a Dam