A look back at the early spring: After demolishing the heads and lock chambers at the Ruhlsdorf, Leesenbrück and Grafenbrück locks, the sludge was removed from the excavation pits a few weeks later. For this purpose, divers were deployed even in frosty temperatures to pump the large quantities of fine sediment into sedimentation basins using suction trunks in laborious manual work. Visibility under water is not even 20 to 30 centimetres.
This was followed by the installation of so-called micro-grouted piles in a grid of 2 x 2 meters to anchor the underwater concrete base. These are boreholes that reach between 8 and 13 meters deep under the future underwater concrete base. Steel rods with a diameter of 5 centimetres are then inserted into these boreholes, grouted with a cement slurry and later secure the excavation base against floating after draining.
