MAXIMA is a €1bn wastewater project in Malmö, Sweden, which will see the construction of a new 5km-long wastewater tunnel together with two shorter connection tunnels, 11 shafts, a major pumping plant and a treatment plant. Named after an early Roman wastewater system, Cloaca Maxima – which translates as ’Greatest Sewer’ – this will be one of south Sweden’s biggest infrastructure projects.
Client VA SYD, which brings together several municipalities that will be served by MAXIMA, is due to submit its environmental application for the project by the end of May, with the approval process taking approximately two years. In the meantime, VA SYD is keen to talk to contractors about the scheme and how tenders might be procured. It has yet to decide how the project will be divided up and what form of contract will be used.
“It is about finding the right chemistry between the client and contractor and putting the risks where they can be best managed,” says VA SYD programme director Gitte Isacsson. “We are looking for companies that can work in cooperation, looking at solutions in a constructive and open-minded way.”
The area’s existing sewage systems were built in the 1950s and are now over capacity. This means that there are frequent overflows of combined wastewater and stormwater into canals and the harbour, even after relatively small amounts of rainfall. Furthermore, the population of this area – which is linked to Copenhagen by the Öresund Bridge – is growing fast.
“With the existing system, we are polluting our water and that needs to stop,” says Magdalena Beck, representing the city of Malmö. “This is most of all about our children and their future.”
The main tunnel will be 5m in diameter and will run through Copenhagen and Bryozoan limestone. The client’s designer Sweco, with specialist Austrian tunnelling subconsultant iC, is suggesting that an earth pressure balance (EPB) tunnel boring machine will be best for the job due to the high groundwater table and faulted rock.
EPBs were used to drive the twin tubes for Malmö’s Citytunnel railway project. “The two TBMs for the railway were completed in the same geological conditions, so we have a good reference project,” says Gitte Isacsson who worked on the Citytunnel project. “We completed that one year ahead of schedule and €100m below budget.”
The two shorter tunnels, each 1km long and 2.2m in diameter, will be pipejacked. Pressurised pipes will bring water from the various municipalities via drop shafts, travelling by gravity to the main 42m-diameter, 30m-deep shaft where it will be pumped up to a new treatment plant. The construction of the treatment plant at Sjölunda will be a logistical challenge, says Gitte Isacsson, since the existing treatment plant must remain fully operational throughout construction.
With the environmental application made, the next milestone will be the formal decision to go ahead with the project, expected at the end of 2023. The new system should be in operation by 2032.