Scope outline for the contract E70 Norhtern wastewater tunnel

• 10.5 km main tunnel from S37 Källby to S01 Sjölunda pumping station, with an internal diameter of approximately 3 meters
• 4 shafts
• 3 connection chambers at ground level for connection to the existing pipe network
• 4 ventilation facilities at the shafts

Shafts

Shaft S32 will serve as the launch shaft for tunnel boring, first southward towards S01 and then northward towards S37, as well as for spoil removal. The remaining shafts are connection shafts where the existing sewer network is connected to the tunnel system. The shafts will also enable monitoring of airflow.

Tunnel

The tunnel is designed for gravity flow, lined internally with concrete, and constructed as a watertight structure. Concrete in wastewater tunnels is exposed to an aggressive environment with moisture, chemicals, and microbiological processes. In particular, sulfuric acid formed in wastewater systems can cause chemical deterioration of the concrete. The required technical service life is 100 years.

Geology

The tunnel is bored through both limestone and consolidated soil layers, known as Alnarp sediments. The geological profile is shown in the image below.