In July last year, Porr was awarded Lot 2 for the project at the Rudolf Fettweis plant in Forbach, in the Black Forest. The contract 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.

Porr project manager Torsten Schmuck said in order for the mining work to start on time, several challenges needed to be overcome.

“We have to plan and organise up to four parallel tunnelling operations in a complex tunnel, shaft and cavern system. Occupational safety is also very important. We are therefore setting up a rescue team with our own construction site staff that can act safely and quickly in the event of danger on the mountain. The permits for residential and explosives storage facilities as well as water law permits also involve considerable effort,” said Schmuck.

On the factory site (construction site 1), Porr is securing a slope under the B462 federal road with shotcrete and soil nails. The main access tunnel to the cavern will be constructed from this site.

In the slope areas north and south of the rubble tunnel (construction site 2), safety nets and safety fences are being installed. The material resulting from the work in the mountain will later be transported away through this tunnel.

Porr’s €98.3m (US$107m) contract is part of a €280m investment by EnBW Energie Baden-Württemberg. The heritage-protected Forbach run-of-river power plant was commissioned in 1914 and converting it to a pumped storage power plant will significantly increase its efficiency.