How the southern wastewater tunnel is built – step by step
The southern wastewater tunnel will run from Turbinen in Malmö to the Sjölunda wastewater treatment plant, with microtunnels connecting from Värnhemstorget and Spillepengen. The tunnels will handle wastewater from the city of Malmö as well as parts of Svedala municipality.
The tunnels will be built in four stages – here’s how it works and how the surroundings are affected:
1.Preparing the ground
How it works
The ground where the shafts will be constructed must be carefully prepared before construction can begin. The area is first fenced off and measures are taken to ensure that traffic flows around the site function properly. The work area is cleared, any utilities that need to be relocated are moved, and preliminary excavation is carried out to a depth of a few meters to check for obstacles, contaminated soil, or anything else that could risk delaying construction.
When does this happen?
When tunneling, the boring machine needs to be lowered into a special launch shaft, which is often built first and is larger than the other shafts. For the southern tunnel, the launch shaft will be located where the Sjölunda pumping station will later be built, and ground works are planned to begin here no earlier than the end of 2027. This will be followed by preparing work areas for the remaining shafts, including those for the microtunnels from Spillepengen and Värnhemstorget.
Impact on the sourroundings
During daytime, some construction noise may occur near the work areas. Traffic on connecting major roads may periodically increase throughout the construction period due to transport to and from the site, and minor traffic disruptions may occur. No road closures are planned.
2.Construction of shafts
How it works
The launch shaft Sjölunda pumping station is built first, followed by the remaining shafts along the southern tunnel, including those for the two connecting microtunnels from Spillepengen and Värnhemstorget. The work begins by constructing a support structure forming the shaft wall, using either diaphragm wall technology or secant piles. Once the shaft wall is sealed, the shaft is excavated down to the required level.
When and for how long?
The plan is to begin constructing the launch shaft Sjölunda pumping station no earlier than 2028, followed by the other shafts. Each shaft takes around 6–12 months to build, and activity will continue at each shaft throughout the entire tunneling period.
Impact on surroundings
Work at the shafts is carried out in different phases throughout the construction period. During active phases, noise and vibrations may occur near the shafts, along with transport to and from the site. The total duration of work at each shaft is 2–4 years, and the noisiest activities last for 3–6 months per shaft depending on its size. At the launch shaft Sjölunda pumping station, activities will continue throughout the entire construction period.
The most noise-intensive activities will take place during daytime (07:00–19:00), but some work may need to be carried out in the evening or at night. With protective measures in place, noise levels will in most cases comply with the Swedish Environmental Protection Agency’s requirements. Before noisy activities are carried out, VA SYD will inform nearby residents. Updated information will also always be available on VA SYD’s website under “Operational Information.”
3.Tunnel boring
How it works
Main tunnel: At the launch shaft Sjölunda pumping station, the tunnel boring machine is lowered, and the tunnel is bored under Malmö via shafts at Flintrännegatan, Kosterögatan, Skruvgatan, Frihamnsallén, and Carlsgatan, and finally to Turbinen, where the machine is retrieved.
Microtunnels: A smaller tunnel boring machine is lowered into the shaft at Borrgatan and bores toward the Sjölunda pumping station shaft. It is then retrieved and transported back to Borrgatan, where it is lowered again and bores to the Spillepengen shaft. The machine is retrieved and transported to the Rosendal shaft, where it is lowered and bores to the Skruvgatan shaft, where the microtunnel connects to the southern tunnel. The machine is then retrieved and transported back to Rosendal, lowered again, and bores to the Värnhemstorget shaft, where it is retrieved. The order of these stages may vary depending on detailed planning.
All excavated material is moved backward through the tunnel to the launch shaft, where it is brought to the surface and transported away for handling in accordance with regulations.
When and for how long?
Tunnel boring is planned to begin no earlier than 2029 and will continue through 2031.
Impact on surroundings
Since the tunnels are bored at a depth of 20–35 meters using well-established methods, the assessment is that no existing buildings above the tunnel route will be affected, either during construction or afterward.
Residents directly above the tunnel route may hear a low, rumbling structural sound* for about one week as the tunnel boring machine passes approximately far down below ground. The machine advances about 15–20 meters per day. Once it has passed the building, no further disturbance will occur, neither during construction nor operation.
*Structural sound refers to noise from an activity (such as tunnel boring) that travels through solid materials (like hard soil or rock) into a building’s structure, creating a low-frequency sound.
4.Completion of construction
How it works
Once the tunnels are complete and the shafts have served their purpose, around 2031, these will be closed and left dormant for a couple of years while awaiting completion of the Sjölunda pumping station and wastewater treatment plant. The existing pipe network will then be connected, around 2035. What remains above ground may be a small building or a hatch providing access for service and maintenance.
Impact on surroundings
Some noise may occur, along with increased traffic from transport to and from the work site. No road closures are planned, but short-term closures may occur, for example when connecting to existing pipe networks.