CBD Sewer Augmentation Stage 2, Lonsdale Street

Melbourne’s sewer network is more than a century old and a range of sewer works have been tabled by the Victorian State Government in order to prevent the prospect of an outdated and unusable system. Rob Carr was appointed by CWW in June 2019 to deliver the second instalment of a four stage strategy, to install a secondary 900m long DN1400 GRP sewer line under Lonsdale Street in the heart of Melbourne’s CBD.

Overall, the project involved the construction of a 900m tunnel, completed in two shots, 550m and 350m respectively using a 1500mm outside diameter glassfibre reinforced plastic pipe. Both drives were launched from a 23m deep 6m ID underpinned segment caisson shaft on Lonsdale Street located between King and William Streets in Melbourne’s CBD. The first 550m drive was headed towards a 9m deep concrete secant piled receiving shaft at the intersection of Lonsdale Street and Elizabeth Street. Piling was necessitated to cater for the bespoke shape given proximity to a heritage building, building hoardings, existing services and limited real estate on the road. It was important to maintain a traffic lane wide enough to allow for adequate flow of traffic in the area. The second 350m drive headed towards the intersection of Lonsdale Street and Spencer Street into a pre built shaft, which required excavation and modificaiton to allow for the MTBM entry.

Other works completed on the project included shorter DN700 lines aiding connection to the existing infrastructure, 3m diameter precast GRP manholes, testing and live connection works to same. The work was undertaken directly along Lonsdale Street, which required intricate community and stakeholder management, detailed traffic control, and careful logistical planning to ensure minimal disruption to the surrounding area.