Right:
More than half of the excavation at Forbach has been completed by Porr and the project is to finish at the end of 2027 PHOTO CREDIT:
ENBW, ARTIS ULI DECK
construction might start in early 2024 for a planned
finish of late 2027. Soon after obtaining the planning approval, in May
2023 the owner gave the go-ahead - looking for works preparations and procurement, and wanting the same completion deadline to be met. The total cost of the project was put at approximately €280 million (US$304 million, £246 million - 2023 currencies). First excavation started in April 2024, although it was
not until June that the ceremonial handover of the statute of St Barbara took place and blasting began for the main access tunnel on the Forbach project. Much of the project involves tunnelling to create
new water conveyance tunnels, caverns for a new underground powerhouse, and also storage caverns for water - which the owner says is unique in German hydro. The arrangement of the new tunnels is, upstream,
to take water from two different reservoirs and convey the flows, separately, for operational reasons, to opposite ends of the new powerhouse cavern. The reservoirs to be tapped are the Kirschbaumwasen and Schwarzenbach, respectively. The powerhouse cavern will take their separate
inflows and, with generation equipment dedicated to each, produce electricity. The Kirschbaumwasen inflows will pass specifically and only to three new dedicated Francis turbines in one section of the new powerhouse cavern; the Schwarzenbach inflows will pass, again down that dedicated route, specifically and only to its own part of the powerhouse, to a new pump-turbine. Flows from all equipment will discharge into the
tailrace tunnels. Then, downstream of the powerhouse, the outflow waters will pass through further tunnels and also storage caverns, eventually to be discharged into the river. However, the discharge will be delayed as the caverns
Centre: The project includes excavation of a large powerhouse cavern. Here, anchors are drilled for the rails of the cavern’s high, permanent travelling crane PHOTO CREDIT: PORR
Above: The hydro site is more than 100-years old and underground works are key to the power facility’s next stage of life in the landscape PHOTO CREDIT: ENBW, ARTIS ULI DECK
12 | June 2025
are to hold sufficient water to act an effective ‘lower reservoir’ to Schwarzenbach reservoir, which will be the ‘upper reservoir’ in a pumped storage pairing. The Schwarzenbach pump-turbine will push the flows back up through the dedicated connecting tunnel, at suitable times.
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