The Taum Sauk Reservoir had a Niagra Falls style overflow on September 26 at the same spot that collapsed on December 14 — one day after the reservoir received an engineering award.
The St. Louis-Post Dispatch reports:
The Sept. 27 e-mail from Richard Cooper, superintendent of Ameren’s Taum Sauk Hydroelectric Plant, said the overtopping two days earlier had washed away rock at the base of the reservoir wall. Eroded trenches were a foot deep in some areas.
Cooper’s e-mail, sent to several Ameren supervisors, said employees described the incident as “Niagara Falls.”
“Overflowing the upper reservoir is obviously an absolute ‘NO-NO,’” Cooper’s e-mail said, noting that it would “cause eventual failure . . . Those kind of headlines we don’t need.”
The article notes Ameren the overflow to federal regulators.
The Post-Dispatch got the emails from Don Giljum, business manager for Operating Engineers Local 148, the union that represents Taum Sauk workers.
Dam expert Charles Morris, a civil engineer at the University of Missouri at Rolla, said any previous overtopping at Taum Sauk should have set off red flags.
“That structure was not designed to be overtopped. Period. If it did so, (Ameren) should have gone berserk,” Morris said. “If they knew about it, they were very negligent.”
Earlier articles had noted that the reservoir was leaking from the start and a liner had to be placed.
The Post-Dispatch quoted an Oct. 7 email from Cooper saying a gauge to monitor the reservoir was failing.
“This bend in the pipes gives us a false reading and causes the reservoir level to look lower than it actually is,” Cooper wrote. “Until these pipes can be re-attached we are lowering the pumpback shutdown setpoint to 1594 down from 1596. We want to give ourselves enough cushion so that we won’t pump over the reservoir walls.”
Further it notes:
At an elevation of 1,594 feet above sea level, employees thought the reservoir was within three feet of the crest, which is 1,597 feet.
But according to other Ameren data obtained by the Post-Dispatch, the instruments may have registered a 3-foot cushion that didn’t exist.
The data show the reservoir reaching an elevation of 1,594 feet at 5:08 a.m. on the morning of the failure. Four minutes later, pumping stopped — with water levels still at 1,594 feet. One minute after that, at 5:13 a.m., water levels dropped as the breach occurred.
The makes note of the USGS photographs UM-Rolla engineer Dave Hoffman who noted that gullies with grass growing below the reservoir indicated there had been breaches over time on the rim of the reservoir.
In a 2003 report, inspectors with a Chicago firm barely touched on the instrument problems, stating the instruments were “not well documented on drawings.” Yet FERC gave Ameren passing marks, even though inspectors found settlement and shifting of concrete panels around the northwest part of the kidney-shaped reservoir.
Also, Taum Sauk has never been monitored 24 hours a day. Most of Taum Sauk’s instruments are connected wirelessly to Ameren control stations in St. Louis and Osage.
In fact, Taum Sauk managers recently won an electrical engineering award that marveled at the way the plant was run via “remote control.”
That award was presented on Sept. 26, one day after employees discovered the “Niagara Falls” overtopping.