In December 2005, a 700-foot section of the dam surrounding the Taum Sauk upper reservoir failed and released 1.4 billion gallons of water down Proffit Mountain and into Johnson's Shut-Ins State Park in Annapolis, Mo. After a period of investigation and planning, AmerenUE formed a team for the dam rebuild.
Because much of the old dam remained in place, it was decided rock from the original construction could be used as aggregate for the newly designed roller-compacted concrete (RCC) dam. Five batch plants were set up; two inside and three outside the old dam.
Four produced the RCC mix and one produced conventional concrete. All five batch plants ran simultaneously, and each plant averaged about 10,000 to 12,000 yards of concrete per day.
As work continued on the excavation, rock from the existing dam was hauled to a crushing operation that processed the material into two stockpiles. This was used in the RCC mix. About 6 million tons of the existing rock was recrushed and used, resulting in minimal waste and eliminating the need to haul any materials from the site.
Fly ash was recovered from a waste pond at a coal-fired power plant owned by AmerenUE for use in the new RCC mix, thereby creating a renewable resource from the waste product. One hundred pounds of fly ash was used in every cubic yard of RCC, resulting in the use of 160,000 tons of fly ash.
Eventually, 2.8 million cubic yards of RCC, 160,000 tons of fly ash, and 300,000 cubic yards of conventional concrete were used to rebuild the dam.
Owner: Ameren Services, Sunset Hills, Mo.
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