This massive mountaintop project relies on the ability to pour concrete even in cold weather, and that’s where Ware’s equipment plugged the gap for the Taum Sauk Dam.

It takes a lot to “wow” Greg Reynolds, who has been traveling around the country helping Ware customers for 18 years. However, the Taum Sauk reservoir built into the top of a mountain impressed him.

The Taum Sauk plant is a pumped-storage hydroelectric plant, operated by the AmerenUE electric company. Hydroelectric power generation is used by some power plants to store excess electrical power during low demand periods for release as demand rises.

The Taum Sauk was designed to help meet peak power demands during the day from AmerenUE customers. The generators and turbines at river level are reversible, and at night, the excess electricity available on the power grid was used to pump water back to the mountaintop.

On the morning of December 14, 2005, the Taum Sauk Dam failed, releasing a billion gallons of water in twelve minutes and sending a 20-ft crest of water down the Black River.

The dam, located in the St. Francois mountain region of the Missouri Ozarks approximately 90 miles south of St. Louis, is being replaced with a roller compacted concrete dam and construction is just over 50% complete three years later.

Ware is assisting in the rebuild, providing two 250-hp boilers to heat water to enable the company to pour concrete in the cold weather.

Reynolds marvels at the amount of concrete that is being poured as part of this project. The rebuild calls for more than 3 million cubic yards of concrete, of which 2.7 million cubic yards is roller-compacted concrete (RCC) and will be used for the core of the dam.

The boilers help produce seven cubic yards of concrete every 47 seconds — that is the equivalent of one concrete truck full of concrete in less than one minute.

Because the project required such a large amount of concrete, it was necessary to have concrete batch plants on site. Four batch plants are on site — three that hold the RCC mix and one holding the conventional concrete mix.

HISTORY OF THE TAUM SAUK PLANT

The Taum Sauk plant is unique because it is a pure pump-back operation, meaning that unlike most other pumped storage sites, there is no natural waterflow available to aid in power generation. It was among the largest such projects when it was built in the early 1960s. The two original reversible pump-turbine units were each capable of generating 175 MW of power. They were upgraded in 1999 to units capable of 225 MW each.

The reservoir had been lined with a membrane in 2004 to minimize water leakage; prior to that, it had been losing water for some time. When fine material is washed out of a reservoir structure, it is known as “piping.” When piping occurs, the reservoir structure can settle in or slump, which means water may start flowing over the top.

When the failure occurred in 2005, a triangular section on the northwest side of the upper reservoir failed. According to AmerenUE, a computer software problem caused the reservoir to continue filling even though it was already at its normal level. In addition, there was minor leakage through the dam walls over a prolonged period that had carried away fine material in the walls, weakening the reservoir’s holding walls. Piping ultimately creates voids in reservoir walls and causes the walls to slump and fail. The failure of the reservoir occurred as it was being filled to capacity.

No fatalities were reported, although there were several injuries. The dam of the lower reservoir held, trapping much of the deluge. If it had given way, then towns downstream, including Lesterville and Centerville, would have been in grave danger.

The rebuild is due to be completed in 2011. TB

Contact Ware (Louisville, KY) at 800-228-8861, or visit the company's website at www.wareinc.com. Ameren Corporation NYSE: AEE was created December 31, 1997 by the merger of Missouri’s Union Electric Company (formerly NYSE: UEP) and the neighboring Central Illinois Public Service Company (CIPSCO Inc. holding, formerly NYSE: CIP).[1] It is now a holding company for several power companies and energy companies. The company is based in St. LouisAmeren is a portmanteau for “American” and “Energy.”˙