The event was distinctly different from the Dec. 14 reservoir failure that resulted in significant flooding," says Voss. In addition, contrary to news reports, the integrity of the reservoir structure was not weakened by the wave action."
He adds that in the days and weeks following the event, the plant was closely monitored and after the event, the company immediately took several remedial actions, including dropping the water levels by two feet to avoid overtopping the reservoir.
At every step of the way, on and after Sept. 25, our employees took steps they believed were sufficient to protect the facilitys safety," Voss says. In hindsight, those steps proved inadequate to avoid the Dec. 14 overtopping that resulted in significant damage to the Johnsons Shut-Ins state park and injury to a family of five.
Here are key findings from AmerenUEs initial investigation of the event:
"Contrary to media reports, the event did not cause the event of Dec. 14 and was not a result of pumping water over the top of the reservoir; instead, the water spilled on was the result of wave action due to high winds from Hurricane Rita and slightly elevated reservoir levels. In addition, the company has found no evidence to indicate that water had ever been pumped over the top of the upper reservoir prior to Dec. 14.
"Following the incident, the company reviewed instrumentation reports, discovered problems with the sensors indicating water levels in the upper reservoir and lowered set points for those water levels.
"AmerenUE did not report the wave action of to FERC because the company did not believe that this condition was a reportable incident.
FERC last inspected the facility in August 2005---before the wave action event on Sept. 25.
Voss also added that the company has always accepted full responsibility for the Dec. 14 breach. Since Dec. 14, company officials have enlisted the help of a number of experts and worked with local, state and federal agencies to determine the cause of the incident and the next steps for repairing the damage to the state park and the Black River. Some of the accomplishments of state and company representatives assigned to the project include:
With the Missouri Department of Natural Resources, Ameren staff and contractors have been working seven days a week to remove soil and trees from roadways, parking lots, trails and other areas of the park. Approximately 122,000 cubic yards of woody debris have been mulched. More than 6,000 cubic yards of sediment have been removed. Most of the paved areas within the park have been cleared.
The goal of much of the restoration effort is to prevent additional sediment from entering the Black River and any bodies of water feeding into the Black River. Crews have been lowering the water level of a six-acre pond formed at the base of the mountain by the force of the water coming down the mountain. This is being done to make sure that any future natural high water events do not wash silt into the East Fork of the Black River.
Crews have rebuilt walkways and are cleaning up campground buildings and other facilities and have replaced fencing around a cemetery.
To restore the highly valued "fen" - a forested wetlands with distinct features and vegetation--crews have been removing debris and sediment manually, literally by hand. Crews are evaluating use of vacuum devices to remove sediment from surfaces.
AmerenUE applied for, and was granted, permission to treat the lower reservoir with materials (alums) that will cause the fine clay particles that are suspended in the water to clump together and fall to the bottom of the reservoir. This will keep these particles from going into the East Fork of the Black River and further muddying that river. An implementation plan developed and filed with the Missouri Department of Natural Resources is being reviewed. The plan could be implemented as early as next week.
At a Dec. 14 media conference call, Ameren Chairman and CEO Gary Rainwater shared preliminary thoughts about the cause of the breach---an instrumentation failure causing water to be pumped over the top of the reservoir. However, he emphasized then and again stressed today that those statements were preliminary.
"We now need to allow representatives from several state and federal regulatory agencies to fully analyze the incident and complete their review before we can precisely establish the cause and determine the best course of action," he said. The FERC will issue a full report and share that publicly after it has been independently reviewed. That effort could take weeks. And while we do this exhaustive analysis, we do not think it is constructive for the company or others to speculate about the cause of this incident.
"Finally, there have been allegations in the media that the Federal Energy Regulatory Commission or some state agency should have acted to prevent the Taum Sauk disaster. We dont believe that any governmental agency was at fault in this incident. We have assumed responsibility for the effects of the breach and are moving as quickly as possible to repair the damage caused by the breach."
Rainwater requested continued patience on the part of the public as all regulatory agencies and the company work to complete this investigatory process.
On Dec. 14 the AmerenUE Taum Sauk Plant experienced a breach in the upper reservoir that caused flooding in the Johnson Shut-ins and resulted in the closing of one road. The plant??s 1.5-billion-gallon upper reservoir experienced a rupture in the northwest corner causing water to flow downward. The company implemented its emergency plan and assembled a multi-disciplinary team of experts, company officials and consultants to analyze the event and determine next steps.
Built in 1963, AmerenUEs Taum Sauk is a "pumped-storage" hydroelectric plant.
It stores water from the Black River in the upper reservoir, built atop 1,590- foot-high Proffit Mountain, and releases the water to generate electricity when power is needed. The plant employs 12. The water flows down a mile-long tunnel inside the mountain, turning turbine-generators to produce electricity. When power demand is low, the same turbines run in reverse to pump water back to the upper reservoir.
AmerenUE is a subsidiary of St. Louis-based Ameren Corporation. Ameren companies serve 2.3 million electric customers and 900,000 natural gas customers in a 64,000-square-mile area of Missouri and Illinois.