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Taum Sauk Reconstruction
 Built
in 1963, the Taum Sauk Plant, located in Missouri approximately
90 miles south of St. Louis, is a pumped-storage hydroelectric plant.
It stores water from the Black River in the upper reservoir, built
atop the 1,590-foot-high Proffit Mountain, and releases the water
to generate electricity.After a catastrophic failure on December
14, 2005 releasing 1.2 billion gallons of water and flooding the
Johnsons Shut-Ins state park near Lesterville, Missouri, the owner
hired Paul C. Rizzo Associates, Inc. (Rizzo) to investigate the
cause of the upper reservoir earthen dam failure.
 Rizzo
determined that substandard construction and instrumentation problems
were partly responsible for the failure. A repair of the existing
dike was not technically feasible due to flaws in the original construction.
Reopening the plant required a complete re-build of the upper reservoir.
In August 2007, the US Federal Regulatory Commission
(FERC) issued a conditional approval for AmerenUE, owner of Taum
Sauk Reservoir, to start preparing to rebuild the upper reservoir.
Rizzo evaluated several alternates for a re-build and selected a
symmetrical (0.6H to 1.0 V upstream and downstream) roller-compacted
concrete (RCC) dam with conventional concrete facing. The existing
rockfill dike material will be processed and utilized to create
aggregate for the RCC. The RCC mixture is estimated to contain 100
pounds of cement and 100 pounds of fly ash per cubic yard. The fly
ash will be excavated and processed from an existing AmerenUE facility.
In addition to cost savings by not having to purchase commercial
fly ash, this will create additional landfill space for use by AmerenUE.
The project is being built by Ozark/ASI constructors/Fred Webber
joint venture. An RCC test section to evaluate RCC mix proportions,
treatments at lift joints, forming for and placement of conventional
concrete facing, control joints, and contractor methods of placing
and compacting RCC was completed in August 2007. Testing of manufactured
specimens and specimens obtained from the test section are underway.
It is anticipated that RCC placement would start in October 2007
and the project would take two years to complete. Approximately
2.6 million cubic yards of RCC and 300,000 cubic yards of conventional
concrete are needed to rebuild the dike.
Additional information related to the project can be found at:
• Owner’s
website
• Designer’s
website
• International
Water Power Magazine website
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