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Ameren workers say computers showed nothing unusual at Taum Sauk


Jefferson City, Mo. – Two former employees of AmerenUE who had the job of monitoring a mountaintop hydroelectric plant said computer readings showed nothing unusual about its water level on an early December 2005 morning, even though water was running over the top of its reservoir.

Attorneys quizzed the man who ordered the power plant to operate and the one who actually manned its computerized controls on Monday. It came during the start of three weeks of hearings by the Missouri Public Service Commission into the collapse of the Taum Sauk reservoir.

Utility regulators are looking into whether the reservoir failure, which washed out Johnson Shut-Ins State Park and seriously injured the park superintendent's family, highlighted a pattern of safety problems at the St. Louis-based utility.

Ameren already has agreed to pay $15 million under a settlement with federal energy regulators. A state Highway Patrol investigation led to no criminal charges from Attorney General Jay Nixon, who instead is pursuing civil damages in state court. The PSC's investigation is separate from the others, though Ameren attorneys have complained it's redundant.

James Bolding, then a power plant dispatcher at Ameren's St. Louis office, said he gave the orders to pump water up to the Taum Sauk reservoir and then ordered it to stop slightly below the targeted water level around 5 a.m. on Dec. 14, 2005. The intent was to drain the reservoir at 6 a.m. and sell the electricity it produced.

There was nothing to indicate anything unusual about the reservoir's water level, which was displayed on a 3-foot-by-5-foot plasma screen in his office, said Bolding, who now works for Ameren's energy marketing subsidiary.

But just after 5 a.m., a 600-foot-wide section of the reservoir wall gave way, after water flowing over its top eroded the wall's base.

Keith Mentel, who was operating the Taum Sauk plant from a control center in a Lake of the Ozarks dam more than 100 miles away, said he alerted the onsite Taum Sauk superintendent to a problem after his computers showed the plant had lost permission to generate power and the water level at the base of the mountain had risen. Only after that did Ameren discover the reservoir had breached.

Some Ameren employees had known for more than two months that some of the reservoir's water-level gauges had broken free from the reservoir wall and were floating with the water, resulting in inaccurate readings.

But Mentel testified Monday that he was unaware the water level readings were inaccurate. He said he also was unaware that separate safety sensors which were supposed to automatically shut down the pumps if the water rose too high had been placed so high as to be rendered ineffective. And Mental said he was unaware certain parts of the reservoir wall were lower than others.

All those things would have been important to know, said Mentel, who retired Aug. 1 after working about 37 years for the utility.

Asked what he believed caused the reservoir failure, Mentel replied: "Basically, I had false indications that morning" about the reservoir's water level.

To compensate for what he described as a "slight error" in the water level readings, Bolding said Ameren had lowered its targeted height for filling the reservoir by 2 feet. On the morning of the failure, Bolding said he ordered the reservoir filling to stop even an inch or so lower than that.

"I felt confident in our routine of filling and lowering the level, and not getting any calls (from plant operators) that water was overflowing, that it was well within the boundaries," Bolding testified during the PSC's administrative hearing.

Like Mentel, Bolding said he was unaware that separate safety sensors had been set too high. Even so, Bolding said he was not relying on those safety probes when giving his directions to raise and lower the reservoir.