A possible pump malfunction may have precipitated a pre-dawn Dec. 14 hydroelectric dam breach and flood near Lesterville, Mo., that injured three people and destroyed at least one home. The plant owner, state and federal authorities are investigating.
The Taum Sauk Reservoir, a 100-ft-high rock-filled, concrete-lined dam covering 55 acres and storing 1.5 billion gallons of water breached at 5:24 a.m. spilling about 1 billion gals of water. A 20-ft-high wave swept down the western side of Proffit Mountain to the Black River and finally into a lower 380-acre storage reservoir, a distance of about two miles. The flood destroyed the home of a park superintendent and injured his three children.
The reservoir is part of a 42-year old pumped-storage peaking plant owned by St Louis-based AmerenUE, a subsidiary of Ameren Corp. During peak demand water from Taum Sauk flows through a mile-long tunnel to generate electricity at the 450-Mw plant. The water is then stored in a lower 380-acre, 2.1-billion gal reservoir then pumped back during the night. In 2004 a polyethylene liner was installed at the upper dam to stem some small leaks.
Ameren officials think something went wrong with the pumping operation and it did not automatically shut off, leading to overtopping and a 600-ft-long breach. "We do not know for certain the cause of the failure," says Gary Rainwater, Ameren chairman, president and CEO. "But it looks like it may have been caused by an instrumentation failure at the reservoir. This is preliminary and we are in the process of bringing in experts to the site to give us a more precise determination."
Federal Energy Regulatory Commission and state Departments of Conversation and Natural Resources also are investigating.