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The plan was to build the largest coal-fired power plant the world had ever seen.

Construction began on the Kingston Steam Plant in 1951 — the Tennessee Valley Authority’s behemoth would supply electricity to Roane County, Tenn. After it was commissioned in 1955, tons of coal passed through the fires inside. Smoke billowed from its stacks. The only thing left to dispose of was the ash left behind.

The TVA built an 85-acre ash pond in 1954 to handle the remnants of the scorched fuel. But the growing hunger for electricity — and therefore coal — outgrew the original ash pond before 1958. So the TVA constructed a more expansive 275-acre pond along the banks of the Emory River.

More than two decades passed, but like the 85-acre pond before it, the new pond filled to capacity. This time the TVA dredged ash from the collec tion pond and began to erect elevated dredge cells with containment dikes to store the accumulating ash.

The elevated cells were built on a foundation of 35 to 40 feet of wet ash, according to an investigation conducted by the TVA. As the earthen dikes pushed higher, the footprint of the cell became progressively smaller. The added height of the pond put more load on the unstable wet ash foundation.