Centralia Coal Mine Dam No 3b

About Centralia Coal Mine Dam No 3b

The primary purpose of Centralia Coal Mine Dam No 3b is tailings. Tailings dams contain waste material from mining operations — typically a slurry of finely ground rock left over after valuable minerals have been extracted. These structures require ongoing monitoring because tailings can contain heavy metals and other contaminants. The dam is owned by Transalta Centralia Mining Llc (public utility). It impounds the Tr-hanaford Creek near Centralia.

The dam stands 140 feet tall and stretches 1,700 feet across, creates a reservoir covering 115 acres, has a maximum storage capacity of 860 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1980, the structure is 46 years old.

This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 08/27/2020.

At 140 feet, this dam is taller than 99% of all dams in the United States.

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