Melbourne is the second-largest city in Australia with approx. four million inhabitants. To increase the capacity of the municipal sewage systems in the northern suburbs, "Melbourne Water" and "Yarra Valley Water" started the "Northern Sewerage Project (NSP)". The project not only took into account urban growth, but also the protection of nearby rivers against wastewater contaminations after heavy rains.
The centerpiece of the NSP includes two tunnels with a total length of 12.5 kilometers that were driven simultaneously. In 2008 Herrenknecht delivered two EPB Shields for the construction of the first section. After best monthly performances of up to 436 meters, the machines achieved breakthrough in 2009 and 2010. On their underground journey, they mastered heterogeneous ground conditions comprising loam and basalt with rock strengths of up to 200MPa, a groundwater pressure of two bar as well as a trouble-free crossing beneath the busy Tullamarine Highway. To reduce the construction noise in the densely populated suburb, the launch shafts have been equipped with noise protection structures.
