More trouble for Ameren's Taum Sauk plant

ST. LOUIS (AP) -- A June fire caused $10 million in damage at a utility's reservoir in southeastern Missouri that was rebuilt after a catastrophic collapse in 2005, according to a memo made public this month.

The St. Louis Post-Dispatch reported Friday that Missouri Public Service Commission staff members learned about a fire at the Taum Sauk reservoir eight days later when they saw damage firsthand during a trip to the facility. The staff members, who were visiting Taum Sauk to discuss the rebuilding of the upper reservoir, filed a complaint against operator Ameren Missouri for failing to report the fire to state utility regulators.

Missouri utilities must report within one day accidents or events at power plants that involve serious injury, death or damage in excess of $200,000. Ameren classified the incident as an outage that did not require immediate notification.

Details about the complaint were highly redacted, so the incident and the extent of the damage at the reservoir became public in a Dec. 16 memo from commission staff to the commission. According to the report, the generating unit had an "extensive fire" on June 6 that melted some stationary parts. Fire crews were sent to the plant, but employees there already had extinguished the fire.

The Taum Sauk reservoir was rebuilt after it overflowed and collapsed in December 2005. It emptied in 12 minutes, and the wash of water swept away the home of a state park superintendent, critically injuring his three children. The reservoir is near Lesterville, about 110 miles southwest of St. Louis. It first started operation in 1963, and the rebuilt upper reservoir was completed in early 2010.

To produce power, water flows down the mountain and turns turbines. At night when electrical demand is low, the water is pumped back to the top of the mountain.

Ameren's vice president of power operations, Mark Birk, said an insulated copper winding inside the generator failed. He said generators were inspected during the rebuilding of the upper reservoir but that repairs did not appear to be imminent.

"Much like a light bulb, these windings will age and fail over time," Birk said. "It is difficult to predict when they will fail."

Ameren says repairs are being made and that it should return to service by late March. Commission staff members and Ameren are working to resolve the complaint, and a report on the status of those discussions is due Dec. 30.

St. Louis-based Ameren has about 1.2 million electric customers, mostly in eastern and central Missouri.

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Information from: St. Louis Post-Dispatch, http://www.stltoday.com