The state capital of Hanover is renovating the tunnel system of the middle and north tunnels of the Ahlem asphalt tunnels. The securing is carried out by backfilling the central and northern tunnels. During the backfilling work, mine water is produced, which must be properly discharged, unless it can be used as feed water for the building material to be introduced in the course of the work.

The expected cavity volume of the central tunnel, which is to be secured by the introduction of building material, is approx. 40,000 m³. A maximum of the same order of magnitude is to be expected with mine water to be lifted.

The expected cavity volume of the north tunnel, which is to be secured by the introduction of building material, is approx. 25,000 m³. A maximum of the same order of magnitude is to be expected with mine water to be lifted.