In 2017, City West Water, the Victorian Government-owned retail water business in Metropolitan Melbourne, increased the capacity of its sewer network to keep up with the demand for essential infrastructure.
With the current sewer in Spencer St dating back more than 100 years and reaching capacity, City West Water opted to install a new secondary sewer main through a 700-metre tunnel with an access shaft at either end.
Tonkin + Taylor assisted with various services, including geotechnical, hydrogeological, and trenchless pipeline construction, which helped steer this sensitive project through an extensive site investigation and design stage.
The service focus included the access shafts for the small-diameter tunnel boring machine, which had to reach 12 metres below road level. Accordingly, Tonkin + Taylor advice addressed several constraints, such as groundwater issues, protecting adjacent structures and challenging ground conditions. Extensive areas of highly fractured basalt across the site demanded great skill in sampling, assessment, and advice regarding constructability issues.
At the same time, the busy inner-city project location meant that the Tonkin + Taylor team had to effectively navigate a multitude of stakeholders related to other underground utilities and above-ground interests alike. It also required that investigations were carried out at night to minimise the project’s impact on the road network and general disruption to the public.
