There are several reasons for the selection of the tunnel route. We aim to build as short a tunnel as possible, with as little impact as possible on people living along the tunnel route.
To be built beneath city land
The tunnel is mainly being built beneath parkland and streets so as to disrupt private property owners as little as possible. A total of about 150 private properties are located directly above the tunnel route.
The tunnel will be constructed along way beneath existing tunnels and lines so as not to affect public transport, the power grid and water pipes, for example.
Must pass Eolshäll
One prerequisite for the tunnel construction is that it must pass the Eolshäll pumping station so that it can connect the wastewater tunnel from Skärholmen.
Overflow points to be removed
Untreated wastewater is released into Lake Mälaren as an emergency measure – overflow discharge – during periods of heavy rainfall, for example. The tunnel route has been selected so that the overflow points along the route can be removed. The amount of untreated wastewater released into Lake Mälaren will decline sharply when the tunnel is complete.
The tunnel will mostly pass through rock and as little as possible through clay areas so as to avoid subsidence. The tunnel route also needs to be adapted in order to pass deformation and crack zones in optimum positions.
As short as possible
After having taken into account the motives above, the tunnel route has been selected so that it is as short as possible, for financial reasons.