Tunneling leaves the surface intact
In fact, there is little traditional about the sewer upgrade, although the aim is the same: to reduce overflows along the 4.3-km sewer route. To expand sewage capacity, most municipalities dig deep sewer pipe trenches. In Hvidovre, however, boreholes are limited, because Ramboll’s specialists have used another method entirely, drilling tunnels through the fissured limestone and other layers instead.
This spring, the tunnelling machine will excavate 970 metres in a single go, one of the longest stretches ever undertaken in Denmark. The tunnelling method will enable Hvidovre residents to enjoy a park and other areas unmarred by a 970-metre-long trench. Neither will the infrastructure be affected, as most of the tunnelling is being done under existing transport corridors, including several residential streets, a four-lane motorway and a railway.
A cheaper and better combination
The new pipeline has a diameter of up to 2.5 metres. Even pipes that big cannot prevent floods in Hvidovre, but nine other municipalities along the Harrestrup stream system are joining forces with Hvidovre on an innovative climate adaption project that will further strengthen the area’s resilience to flooding. The 10 municipalities share a vision where the almost 30-km system of streams with mostly paved edges returns to a natural state with greener banks, clear water and fish – and where sewage sludge only threatens to overflow into the system or nearby basements after exceptionally violent cloudbursts.
“It is unique both in Denmark and Internationally for so many municipalities to be working together on a climate adaptation project like this that also holds big recreational benefits,” says Henrik Søgård Olsen from Ramboll.
The head of Copenhagen’s Climate Unit, Lykke Leonardsen, agrees that the projects are innovative and gives the municipalities and their citizens more for less:
“All our calculations on climate adaptation show that it is cheaper and better for citizens to combine traditional sewer solutions with surface greening initiatives like stormwater storage in parks, recreational schemes and other urban development. In popular terms, you get benefits in two areas, but only pay for one,” says Lykke Leonardsen.