I know this area well. I have camped and floated the rivers for many years there. The damage was in a small area, but some of the best places were damaged badly.
http://www.stltoday.com/stltoday/news/stories.nsf/missouristatenews/story/0A4A827BA5C98DB2862570D7004F9A49?OpenDocumentThe Taum Sauk Hydroelectric Plant consists of a 50-acre lake built atop Proffit Mountain that is connected by a mile-long tunnel to a 300-acre lake at the base of the hill. The upper lake is about 700 feet higher in elevation than the lower one. AmerenUE drains the upper reservoir through generating turbines during times of peak electrical demand, then pumps the water back uphill when demand for electricity is lower.
The Proffit Mountain upper reservoir, at 1,590 feet in elevation, is just west of Taum Sauk Mountain, the highest point in Missouri.
Reservoir, generator built in 1963
Union Electric Co., forerunner to AmerenUE, built the system to great fanfare in 1963, mainly to meet the rapidly increasing popularity of air-conditioning in homes and buildings.
The upper reservoir was built by digging 10 feet into the mountaintop and then ringing the bowl with a crush-rock berm, or thick wall, that is about 80 feet tall. When filled, holds 1.5 billion gallons at a maximum depth of about 90 feet.
The interior, or bowl, of the reservoir is lined with asphalt on the bottom and concrete along the rock berm. Rainwater said the company installed a plastic liner to the interior two years ago to stop minor leaks. He said the rock berm never had been breached before.
But when it did, water cascaded about a mile down the western slope of the mountain and into the east fork of the Black River, about a quarter mile upstream from the Shut-Ins campground.
The flood then roared through the park and downstream about two miles into AmerenUE’s lower reservoir. Rainwater said the flow topped the lower reservoir’s dam by only one foot, which he called manageable. The Black continues flowing southward toward Lesterville.
Flooding could have been much worse
Reservoir emptied in about 12 minutes
The Shut-Ins is on the east fork of the Black River, about a mile downhill from the AmerenUE upper reservoir. The Shut-Ins is a series of rock formations through which the east fork bubbles and cascades. It is a popular swimming attraction, especially for young people, during the summer months.
Rainwater of AmerenUE told reporters that a monitor at the company’s station at the Lake of the Ozarks, where the company generates electricity through Bagnell Dam, indicated that the upper reservoir had been refilled by 5:12 a.m., but had fallen back to low level by 5:24 a.m.
“It had emptied in about 12 minutes,” he said during a news conference at company headquarters near downtown. “We don’t know what could have caused it.”
The breach in the northwestern wall dropped the water level in the upper reservoir by about 70 feet, he said.
The Federal Energy Regulatory Commission last inspected the Taum Sauk upper and lower reservoirs on Aug. 25 and found "the project was properly maintained and operating consistent with the license," said J. Mark Robinson, director of the agency's office of energy projects.
Inspectors review the structures, observing the concrete and looking for any cracking or seepage.
The Taum Sauk dams are considered "high-hazard potential" structures because their failure could lead to loss of life or property.
