According to the FERC filing, construction would begin in 2007, with the plant returning to service in 2009. FERC has indicated that the agency will seek public comment on this filing.
AmerenUE also stressed that the reservoir would be rebuilt following criteria used in current dam design and construction practice. The upper reservoir will be constructed with roller compacted concrete (RCC) based upon a design by Paul Rizzo & Associates; this design satisfies current guidelines established by the FERC.
'We would not be returning this plant to service if we were not absolutely certain that our design met, or exceeded, all modern safety criteria,' said Thomas R. Voss, AmerenUE president and chief executive officer. 'After much analysis, we are now confident that this plant can be returned to service and operated safely to restore a critical source of reliable power to our customers.'
Voss also noted that insurance is expected to cover the costs of the rebuild. He pointed to the plant's economic impact on the nearby community as a source of employment and significant local tax revenue. Taum Sauk Plant also plays a unique role in Ameren's system because of its ability to begin generating electricity in the unlikely event of a loss of grid power.
The decision comes more than a year after the 14 December 2005 breach in the upper reservoir that caused flooding in the Johnson's Shut-Ins State Park. Built in 1963, the hydroelectric plant stored water from the Black river in the upper reservoir, built atop the 484.6m high Proffit Mountain and released the water to generate electricity when power was needed.
The rebuilt dam would include such safety features as
* A crest elevation for the RCC dam design that will be in excess of the highest anticipated water surface, including rain events or high water levels.
* An overflow release structure, to protect against damage to the RCC structure in the unlikely event that redundant control systems fail and the upper reservoir overflows. While the design is not yet final, the overflow release structure is not ever expected to be used. This is because of the multilayered defense in depth that will exist through a combination of technical monitoring systems and daily operating procedures that will be independent of each other.
* Multiple, independent lines of defense - including continuous video camera monitoring of the upper reservoir water levels - to ensure that proper water levels are maintained in both the upper and lower reservoirs. There will also be separate instrumentation and monitoring systems that will be dedicated solely to dam safety.
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