CHATTANOOGA, TN (Times Free Press) -- TVA's pumped storage facility on Raccoon Mountain hasn't worked since March, the result of four cracked rotors.

Officials with Tennessee Valley Authority said Thursday the problem is a design flaw in the 34-year-old, $310 million plant.

The utility took the entire plant offline as soon as a contractor's alert and its own checks found the rotor cracks in one after another of all four generators there.

But the plant's outage was kept quiet until last Friday, when TVA President and CEO Tom Kilgore told financial analysts that the utility had brought two of its idled coal units back this summer to make up for Raccoon Mountain's lost peak-power generation.

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