FERC seeks comment on new Taum Sauk breach report

The Federal Energy Regulatory Commission seeks public comment by June 24 on a consultant panel report on the Dec. 14, 2005, breach of the 408-MW Taum Sauk pumped-storage project.

In preparing its own 134-page report, the independent panel of consultants considered two earlier reports, one a forensic investigation by FERC dam safety staff, and the other a report by consultant Paul C. Rizzo Associates Inc. for project licensee AmerenUE.

“This marks the completion of the first stage of our investigation,” FERC Chairman Joseph Kelliher said upon issuing the report May 25. “Now that we have the facts before us, we will consider what further action is required.”

FERC said it would review the findings to determine their applicability to other pumped-storage projects under its jurisdiction. There are 22 FERC jurisdictional pumped-storage projects.

FERC’s dam safety director convened the panel to establish an independent as-sessment of the technical caus-es of the failure of the upper reser-voir dam, near Lesterville, Mo.

Report points to water level monitors

The report said the primary cause of the breach was overtopping of the dam due to improperly installed and maintained water level monitors. The panel also found emergency backup sensors proved ineffective because they were installed higher than the lowest points along the parapet, allowing overtopping to occur before shutdown.

The report said a secondary cause of failure was the use of marginally stable “dirty” rockfill — containing silt, sands, and gravels — in the construction of the mountaintop dam. The report said the “unforgiving containment structure” could not tolerate the additional pore pressures and erosive effects of overtopping.

The independent panel’s report is on FERC’s Internet site, www.ferc.gov. Comments should include the docket number, P-2277, and can be filed with FERC at 888 First St., N.E., Washington, DC 20426.

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