Katzenberg tunnel - environmental and approval constraints on the recycling of tunnel spoil material / Katzenbergtunnel - umwelttechnische und genehmigungsrechtliche Randbedingungen für die Verwertung von Tunnelausbruchmaterial

In connection with the construction of the Katzenberg tunnel on the new German Railways line from Karlsruhe to Basel, approx. 2.3 million m³ of mostly variable solid rock, some of which was seriously contaminated, was mechanically excavated (EPB shield) with the use of tenside additives, and was recycled with as little harm as possible to the environment. To do this, the recultivation of a limestone quarry was implemented as the technically and economically best and most environmentally acceptable solution. An estimation of hazards with a forecast of water percolation was used to demonstrate that the pollution of nature and environment, particularly concerning groundwater, could be kept to an acceptable level.
The legal situation regarding approvals was unusual, with the permit for the tipping of material excavated from the tunnel being the responsibility of the quarry operator, the geogenic pollution potential of the tunnel spoil mass being the responsibility of the client and for the construction additives used being the responsibility of the contractor. The preconditions for the recycling measures were created in close collaboration with the authority responsible for the approval and also through appropriate contract arrangements. The tunnel excavation spoil, partially with a slurry consistency, was stabilised on the construction site by adding lime, transported along a 2.5 km long conveyor to the quarry and tipped. The measures were accompanied by an environmental auditing programme, which included the drilling of boreholes into the mass of tipped spoil to demonstrate that the forecasts made had been largely met.