Taum Sauk Pumped Storage Project

About this Project

On June 24, 2008, Union Electric Company filed, an application for a new license to continue operation and maintenance of its Taum Sauk Pumped Storage Project. The 442.5-megawatt Taum Sauk Project is located on the East Fork of the Black River and Taum Sauk Creek in Reynolds County, Missouri. The project does not occupy federal land. As discussed below, this order issues a new license for the project. Company: Ameren Missouri 

Incident Description

December 20, 2007 - FERC rules on rehearing of the August 15, 2007 letter order authorizing licensee to start reconstruction and repair of the project's upper reservoir Decision

August 15, 2007 - Construction, with Conditions, authorized for Taum Sauk Upper Reservoir Reconstruction

August 14, 2007 - FERC staff issues Final Environmental Assessment 

On December 14, 2005, at approximately 5:20 AM CST the northwest corner of the Taum Sauk Pumped Storage Project No. 2277 upper reservoir rim dike failed to result in a release of the upper reservoir. The reservoir was reported to have drained in about ½ hour. Approximately 4,300 Acre-feet of storage was released. The breach flow passed into East Fork of Black River (the river upstream of the lower Taum Sauk Dam) through a State Park and campground area and into the lower reservoir. The Lower Taum Sauk Dam was reported to be overtopped and did not sustain damage. Upon leaving the Lower Taum Sauk Dam area, the high flows proceeded downstream of the Black River to the town of Lesterville, MO, located about 3.5 miles downstream from the Lower Dam. The incremental rise in the river level was about 2 feet which remained within the banks of the river.

• The Stipulation and Consent Agreement Between FERC and Ameren, October 2006 - Appendix A: Dam Safety Program
• Close of Comment Period for Taum Sauk Independent Panel of Consultants Report, July 20, 2006
• FERC Independent Panel of Consultants (IPOC) Report, May 25, 2006
• FERC Staff Report, April 28, 2006
• AmerenUE Consultant's Report, April 7, 2006

Project Description

The Taum Sauk project is located in Reynolds County in south-eastern Missouri, about 100 miles south of St. Louis. The project was completed in 1963 as a pumped-storage project, with an upper and a lower reservoir. The lower reservoir operated as a run-of-river reservoir with outflow being maintained at approximately equal to natural inflow provides storage for water to be pumped to the upper reservoir at night or during periods of low power demand. The water volume used to generate electricity is cycled between the lower and upper reservoirs, so the water elevations of the lower and upper reservoirs fluctuate depending on the pumping/generating modes of operation and time of day. The project structures include a concrete faced rockfill dam (dike), that encircles and forms the upper reservoir; a concrete gravity dam impounding the lower reservoir (the lower dam was designed as a spillway with no spillway gates so that floodwaters could safety pass over the dam); a reversible turbine powerhouse; a gravel trap dam located upstream of the outlet canal in the lower reservoir, and a small dike that impounds the seepage collection pond at the toe of the upper reservoir.

The Upper Reservoir is impounded by a kidney-shaped rim dike at the top of a planed-off mountain. The rockfill ring dike has a reinforced concrete liner to reduce seepage through the rockfill and has a maximum section approximately 94 feet high and is topped by a 10-foot high concrete parapet wall. The reservoir bottom has an asphaltic liner that ties into the concrete liner which is on the inside slope of the rockfill dam. The surface area of the reservoir is 54.5 acres with a total storage of 4,350 acre-feet and live storage of 2,560 acre-feet used for the production of power.

The turbine/generator sets are designed to operate in reverse to pump water to the upper reservoir at night. During the daylight peak-demand hours, the turbine/generator sets operate in normal gravity-feed mode to generate electricity.

The upper dam underwent maintenance work during the 2004 construction season. The upstream face of the upper dam was lined with a geomembrane. The purpose of this work was to minimize the leakage through the rockfill dam. This work resulted in a significant decrease in the amount of leakage from the upper reservoir.

FERC dam safety inspectors performed site inspections on December 14 and 15, 2005, where they made an immediate safety evaluation of the lower dam. The lower dam was found to be safe following the incident and had very little water flowing over it as of December 14. FERC will conduct a complete investigation of the rim dike breach.

Action Plan

A breach of the Upper Reservoir rim dike of the Taum Sauk Pumped Storage Project occurred on December 14, 2005, releasing the upper reservoir. FERC staff initiated an immediate evaluation and analysis to first establish the reason for the dike breach and second, determine the appropriate repair to re-establish the project. In addition to an investigation by a team of FERC engineers, an independent panel of consultants will be convened to evaluate and oversee both the forensic evaluation and the design of the project repair. The scope of the action plan for the investigation is as follows:

• Staff engineers were immediately dispatched to the site to ensure the safety of the lower dam and obtain initial information concerning the breach of the upper reservoir embankment dam.
• By letter dated December 15, 2005, the licensee, Ameren UE, was directed to submit a detailed report in accordance with Paragraph 12.10(a) of the Commission's regulations, which includes the details of the incident and information needed to assess the cause of the incident and the appropriate remedial action.
• A FERC project team has been convened to perform a forensic evaluation of the incident and to review the investigations, analysis, design, and construction required to re-establish the upper reservoir, and to address corresponding environmental concerns.
• FERC has established an independent panel of expert engineering consultants to perform a forensic evaluation of the incident and to review the investigation, analysis, design, and construction required to re-establish the upper reservoir.
• FERC will fully coordinate with the State of Missouri dam safety and environmental agencies during the forensic investigation and the design activities of any remedial measures to re-establish the upper reservoir.
• FERC will evaluate the licensee's compliance with all applicable requirements.
• Review the design report, construction plans and specifications, and construction records.
• A forensic evaluation of the breach of the reservoir rim dike and the project operation will be performed, including an evaluation by engineering consultants to determine the specific failure mode.
• A foundation exploratory program will be required to obtain data and information for remedial action.
• The forensic evaluation will include a critical review of the effectiveness of the Emergency Action Plan (EAP).
• Ameren UE will be required to convene an Independent Board of Consultants to oversee the investigations, analyses, design, and construction of the remedial measures needed to re-establish the upper reservoir.
• The results will be shared with the Interagency Committee on Dam Safety (ICODS) whose members include Federal agencies that own, operate or regulate dams as well as the National Dam Safety Review Board which provide grants for State dam safety programs.

Notice of availability of final environmental assessment