The Green Square Stormwater Drain is a new stormwater drainage system built in partnership with Sydney Water and the City of Sydney. Located about 3.5 km south of the city centre, Green Square is one of the City of Sydney’s key urban renewal precincts earmarked for development, which will accommodate about 40,000 new residents and 22,000 new workers by 2030. The Drying Green Alliance is a joint venture formed between Seymour Whyte Constructions (with Rob Carr Pty Ltd), UGL Engineering, Parsons Brinckerhoff and RPS Manidis Roberts to deliver the project.
The project provides for a 2.4km stormwater drain to carry flow from the entire catchment upstream of Joynton Ave and discharge into Alexandra Canal significantly reducing the impact of major weather in the area. Rob Carr was intimately involved with the project through an early contractor involvement process which required the development of detail design, key stakeholder engagement, service interfacing through to the detailed TOC estimate.
Rob Carr ultimately constructed 4km of DN1800 concrete pipeline via microtunnelling in twin and triple parallel formation over a 1.3km section in high water table ground consisting of sand, clays and fill material classified as restricted and hazardous. A critical portion of the work involved Rob Carr proposing an innovative redesign of a section of works to avoid prolonged authority approvals for relocation of existing assets in the area. In this section, Rob Carr constructed 3 tunnels in parallel no more than 800mm apart on a curved alignment. Rob Carr also constructed 5 deep caissons up to 12m in diameter for TBM access and permanent concrete structure installation among other works.