Centralia Coal Mine Dam No 36a Reservoir Report

Last Updated: December 15, 2025

Centralia Coal Mine Dam No 36a, also known as Widco Dam No.


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Summary

36a, is a public utility-owned structure located in Centralia, Washington. Completed in 1989, this earth dam serves as a tailings storage facility for the nearby coal mine operations. With a height of 14 feet and a hydraulic height of 12 feet, the dam has a storage capacity of 90 acre-feet and covers an area of 18 acres.

Situated on Hanaford Creek-Offstream, this dam is regulated by the Washington Department of Ecology and undergoes regular inspections to ensure its safety and compliance with state regulations. Despite its low hazard potential, the dam's condition has not been formally assessed. The surrounding area has a drainage area of 0.1 square miles, with a maximum discharge capacity of 120 cubic feet per second.

Located in Congressional District 03, Washington, Centralia Coal Mine Dam No 36a plays a crucial role in managing tailings from the coal mining operations in the region. While the dam's primary purpose is tailings storage, its design features stone core and soil foundations. As a key component of the local water resource infrastructure, this dam underscores the importance of sustainable management practices and regular maintenance to ensure the safety and reliability of water resources in the area.

Year Completed

1989

River Or Stream

Hanaford Creek-Offstream

Primary Dam Type

Earth

Surface Area

18

Hydraulic Height

14

Drainage Area

0.1

Nid Storage

90

Structural Height

12

Hazard Potential

Low

Foundations

Soil

Nid Height

14
       
Seasonal Comparison

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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.