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Turning water into gold

After years of starts and stops, a massive subterranean power station is taking shape at Goldisthal, Germany.

    Located on the Schwarza River in the southern part of the German state of Thuringia, Goldisthal is the site of one of the largest pump-fed power station projects in Europe. Construction began in 1997, and when the plant goes into service sometime in 2002 or 2003, its four underground turbines will produce 1060 megawatts of energy.
The goal of the ARGE PSW Goldisthal is to create a viable, dependable and environmentally clean source of electric power. By placing the turbines underground, the builders (VEAG of Berlin, Züblin and Walther Bau of Germany and Stuag of Austria) have been able to protect the landscape, avoiding the massive changes that would have been required if the machine buildings were on the surface. According to engineers, an added bonus is that the cavern power station will be more economical to operate.
    Besides the 1060 megawatts of power, the station will provide other benefits, including primary and secondary power regulation within the grid and instant backup power should another station go down. In addition, almost a thousand workers will bring value-added turnover into the area during the construction years, and there will be 50 permanent jobs at the completed site and an additional 80 in local service and maintenance companies. During periods of drought, the reservoir will provide a water reserve of 2.9 million cubic metres and increased flood control during wet periods. Unfortunately, because of the extreme fluctuation of the water levels in the upper and lower basins, the public will not be allowed to use either basin.
    Meticulous planning and execution have been required to create the 55-hectare upper basin, involving damming the river, drilling 4.7 kilometres of tunnels into the mountain and excavating huge amounts of rock. The location of the main turbine cavern, for example, had to be changed to avoid a geological fault. Despite the immensity of the project, it has proceeded in a straightforward fashion. According to VEAG, the project didn't surprise the world with any new technologies or tricks; it was simply a matter of blasting and drilling.

Massive cliff anchors, air-placed concrete and steel mats were used to secure exterior cliffs and some interior passages. The material excavated, more than 300,000 cubic metres, is being used for rock fill for the dams. The exact amount of concrete used will not be known until completion, but the on-site cement plant hustles daily to meet the demand. Once completed, the dams will be greened and landscaped and the administration buildings constructed in the local architectural style.
During and after the construction of the dam, VEAG will continually monitor the local flora and fauna and take active measures to prevent and correct imbalances and disruptions caused by the project. It has already established a foundation in cooperation with the German Association for the Protection of the Environment and Nature to promote environmentally oriented projects in the eastern part of Germany.

Bibos protect mammoth construction site underground

Water management is critical in any underground construction, but it has been especially so in the Goldisthal project. The 4.7 kilometres of tunnels go through several geological layers, causing greater than normal amounts of leakage water. In addition, tunnel boring is done by the "wet method" and the highly abrasive drilling water runs into sumps at the bottom to mix with leakage water and mud tracked into the tunnels by various vehicles. To ensure the smooth completion of the construction, this abrasive, muddy medium must be continuously pumped out of the sumps.
The ARGE PSW Goldisthal joint venture chose Flygt submersible pumps of the Bibo series for this task. Forty pumps from 2.2 kW to 8.0 kW have been in continuous operation since 1998. The heads are up to 40 metres and the capacities are up to 50 m³/h. Six Flygt Bibos 2151 (20 kW) with a head of around 40 metres and a total of 400 metres of hose are on order and will soon be added.