Green Square

Project Location

Zetland, NSW 2017
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Project Description

The Green Square Stormwater Drain Project is being delivered by the Drying Green Alliance (comprising client partners Sydney Water and City of Sydney, with UGL Engineering, Parsons Brinkerhoff, RPS Manidis Roberts and Seymour Whyte Constructions). Rob Carr was engaged as a subcontractor to the Drying Green Alliance, and delivered a new 2km stormwater drain that will reduce hazardous flooding in and around the new Green Square town centre area. In delivering the new stormwater drain system, Rob Carr microtunnelled nearly 4km of DN1800 concrete jacking pipe (550m of twin parallel lines and 964m of triple parallel lines), constructed five caissons (varying diameters between 10–12m, depths between 7–10m), constructed complex civil structures within the caissons and completed eight conventional shored shafts (up to 6m deep). The works were completed in extremely difficult conditions as the new town centre is located on a floodplain that was once a network of swamps, wetlands and creeks. This meant working in high water table ground that was classified as restricted and hazardous. The team also had to contend with other ground condition variables, such as brownfield sites full of buried industrial waste (e.g. timber, concrete, sand stone blocks and metal objects) that repeatedly stalled works, increased program pressures and added to constrained project site pressures (often next to live traffic or adjacent works). Rob Carr—as an affiliated company to Seymour Whyte Constructions (an Alliance Partner)—worked closely with the Alliance in 2014 during the Expression of Interest and design stage to submit a competitive bid for the project. During the Detailed Design phase, Rob Carr provided frequent input to the stormwater pipeline and box culvert components of the project. Rob Carr’s trenchless solution offered an alternative, value for money approach with significantly reduced environmental impacts (e.g. reduce requirements to excavate Asbestos Contaminated Materials) and lessened (comparatively) community disruptions. Of all the competitors for the bid, the Alliance was the only one to offer a mainly trenchless solution that provided close to $100 million in cost savings to the project. This and the many innovations on the project contributed to the project’s Civil Contractors Federation NSW Earth Awards 2018 (Category 4 – projects valued between $10 million–$30 million) win.


Status
Completed

Duration
March 2015 – May 2017

Client
Sydney Water / City of Sydney

Value range
>$25 million