Scope outline for the contract E80 Southern wastewater tunnel

• 5.5 km main tunnel from S15 Turbinen to S01 by Sjölunda wastewater treatment plant, with an internal diameter of about 5 meters
• 2.5 km of pipe jacking tunnels with an internal diameter of about 2 meters
• 11 shafts
• 5 connection tunnels between shafts and the main tunnel
• 9 connection chambers at ground level for connection to the existing pipe network
• 3 short trenchless connections at S12 Skruvgatan, S14 Carlsgatan, and S16 Värnhemstorget
• 9 ventilation facilities at the shafts

Shafts

Shaft S01 will serve as the launch shaft for excavation of the main tunnel and for spoil removal, and will subsequently house the Sjölunda pumping station. The remaining shafts are connection shafts where the existing pipe network is connected to the tunnel system, except for S20, which is constructed solely to enable excavation of one of the microtunnels. The shafts will also provide the possibility to monitor airflow.

Tunnels

Two bored microtunnels will be connected to the main tunnel. The tunnels are designed for gravity flow, lined internally with concrete, and constructed as watertight structures. 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 tunnels are expected to be excavated in limestone. The geological profile is shown in the image below.