Green Square, between Sydney Airport and the city centre, is one of Australia’s largest urban renewal developments.
The City of Sydney is investing billions of dollars to transform Green Square from an industrial heartland into a vibrant, sustainable and connected hub. By 2030, the urban renewal will create 30,500 new residential dwellings housing an anticipated population of 61,000 people.
As Green Square sits on a floodplain, one of the first major infrastructure projects is to build a stormwater drain. The two-kilometre stormwater drain will carry floodwaters from South Sydney into Botany Bay. The project is in a heavily built up and densely populated area.
Enabling Urban Renewal
The City of Sydney and Sydney Water formed an alliance with WSP, Seymour Whyte Constructions, UGL Engineering and RPS Manidis Roberts to build the Green Square Stormwater Drain. The Drying Green (DG) Alliance developed an innovative design and construction solution that:
- Ensures community safety during floods
- Minimises the impact on the community during construction
- Enables the urban renewal at Green Square to proceed
The underground stormwater drain stretches from Epsom Road in Zetland to the existing stormwater system at Alexandra Canal in Alexandria. Our design team proposed a combination of micro-tunnelling and open trenching to install twin and triple 1800mm diameter reinforced concrete jacking class pipes in parallel. This innovation replaced the reference design that had used open trenched box culverts.
Collaborating to Solve Technical Issues
The DG Alliance worked in collaboration with Sydney Water and City of Sydney through a complex process of optioneering and hydraulic analysis to solve many technical and community interface issues. Our team completed computational fluid dynamics (CFD) modelling and physical modelling to address many of the technical issues.
Achieving Sustainable Outcomes
Micro-tunnelling uses a tunnelling machine to install pipes underground without disturbing the surface. This method reduces the impact on the residents and businesses during construction as well as reducing the environmental impact.
We designed the channel widening and replacement of a restrictive culvert with a bridge near the Alexandra Canal outfall, which has reduced local flooding in the area.
Overall, the new stormwater drain will increase the livability, accessibility and amenity of Green Square’s future town centre as well as significantly reducing the risk of flooding.