The €98.3m (US$107m) contract is part of a €280m investment by EnBW Energie Baden-Württemberg to convert and expand the Rudolf Fettweis Plant in Forbach, in the Black Forest.
Lot 2 includes construction of mined caverns, water reservoirs and tunnels, the shell of the power plant cavern, construction of two pressure shafts, and foundation engineering work. Before the new power plant can go into operation in 2027, the Porr team will have to blast and excavate huge cavities and tunnels in the rock. An estimated 450,000m3 of rock excavation material will be produced.
The tunnel system has a total length of 5.2km. In addition, about 510m of shafts will be constructed using the raise-boring method. The volume of the underground water reservoirs is 200 million litres. The main tunnel alone will have a length of 946m and a cross-section of up to 71.72m2. In addition, there will be six side tunnels as well as access tunnels, supply tunnels and tunnels for energy transmission.
Construction will start in autumn this year.
Porr has experience in building pumped storage power plants, such as Limberg III in Kaprun.
“Pumped storage power plants are a particularly effective solution for generating alternative energy. They are therefore an important building block for the energy transition,” said Karl-Heinz Strauss, CEO of Porr AG.
The heritage-protected Forbach run-of-river power plant was commissioned in 1914; converting it to a pumped storage power plant will significantly increase its efficiency. Until now, after the water from the Schwarzenbach and Murg dams passed the turbines, it flowed into an equalisation basin and then into the Murg. The new underground sub-basin will serve as an indirect power reservoir and from there the water can be circulated as often as required.
