STORMWATER DRAIN KEEPS GREEN SQUARE DRY
27 Feb 2020
Another milestone in the growth of Sydney’s Green Square is the completion of a stormwater system that addresses the site’s challenges as a floodplain once made up of wetlands.
In November 2019, City of Sydney officially opened the Green Square stormwater trunk drain. This two-kilometre trunk drain is a critical piece of infrastructure, installed due to the fact that Green Square is located on a floodplain that used to be a network of wetlands and creeks. Intensive urbanisation has increased paved areas in the precinct, drastically reducing natural drainage for stormwater on the site.
After researching multiple options, the City of Sydney and Sydney Water decided to construct an underground drain from Epsom Road in Zetland to Alexandra Canal, through the new Green Square town centre.
Without this trunk drain to reduce the risk of flooding in the area, Council’s plans for the urban renewal of Green Square – including the City’s $1.3 billion investment in infrastructure – would not have been possible. 
Micro-tunnelling was used to install huge 1.8m diameter pipes laid up to depths of 12 metres underground. Like keyhole surgery for the construction world, micro-tunnelling drastically reduces disruption to existing infrastructure and life above ground.
Complex computer and physical modelling was used to navigate over 1500 pipes and pits to ensure the system worked.
The new drain also diverts stormwater to a new recycled water treatment plant, which delivers up to 320 million litres of recycled stormwater each year to new buildings and open spaces in the town centre. The stormwater is treated in two large gross pollutant traps, resulting in improved water runoff quality.
The $140 million trunk drain project was delivered by the Drying Green Alliance, formed by the City of Sydney and Sydney Water, which includes state government, construction contractors and designers.
Via City of Sydney
