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New tunnel system to flood proof Sydney’s newest town centre
TUNNELLING has started in Sydney on the first major flood prevention project since torrential rains devastated parts of Sydney and the Hunter Valley in April. The work will flood proof the Green Square Town Centre, the first new town centre built in central Sydney for more than a century.
A 2.4km-long underground drain, big enough to empty 300 bathtubs a second, is designed to dissipate flash floodwaters, like those that trapped drivers just 4km from Sydney Town Hall. 
Two months after rescuers in Zetland waded through chest deep waters to pull people from submerged vehicles, the City of Sydney and Sydney Water has started tunnelling on the biggest drain built in the city for decades.
Underground tunnelling machines will excavate the drain that will carry up to 30,000 litres of stormwater per second to Alexandra Canal.
The tunnel will take floodwaters away from Green Square – one of the fastest growing residential areas in NSW – and allow safe construction of the Green Square Town Centre.
Green Square Town Centre is located on what is known as the Waterloo Swamp flood plain between the city and Sydney's Kingsford Smith Airport, where heavy rain can cause hazardous flooding sometimes more than 2m deep.
Lord Mayor Clover Moore said the City had worked closely with Sydney Water on this vital project to transform Green Square, making it even more attractive to developers.
“The torrential storms in April were a graphic reminder of how vital this trunk drain is to make this area a great place for thousands of people to live and work safely,” Lord Mayor Moore said.
“This area was once Sydney’s industrial heartland, but now a lot of the industry has left and new jobs and residents are moving in and making this our fastest growing village,” Ms Moore said.
“At a cost of more than $90 million, this project is a key component of the City’s $440 million transformation plan for new infrastructure and community facilities to ensure the Green Square neighbourhood is a great place to live, work and enjoy.”
Developers building the Green Square Town Centre praised the City and Sydney Water for constructing the drain they said would transform one of the fastest growing residential areas in the state.
Ms Moore said tunnelling machines are traditionally given a woman’s name and the Green Square machine has been named ‘Mary Veronica’ in recognition of Mary Veronica Neilson. Mrs Neilson was the area’s first female alderman (1945–1948) and first female Mayor (1946 and 1947) when she served on Waterloo Municipal Council.
Mrs Nelson’s granddaughter, Janine Loyzaga, said her grandmother had worked hard to improve the community and would have been honoured to be part of this project.
“Mary Veronica was a woman of strong views and strong opinions, and a leader in community service in a time when it was still unusual for a woman to be any of those things. She would have been proud and appreciative to have her contributions to her community recognised,” Mrs Loyzaga said.
The tunnelling machine was be lowered into concrete-lined launch pits in late June, from where it began working below the water table, digging through Botany sands.
Controlled by computers above ground, the micro tunnelling machine will travel about 12-15m a day digging a hole 2.15m in diameter which is lined with concrete pipes.
Up to three micro tunnelling machines will be used together and in some areas three tunnels will be placed side by side to cope with huge volumes of water. Tunnelling is due to finish by the end of 2017.
To minimise disruption to traffic and the community, the tunnelling machines will work well below the surface avoiding the need to dig-up roads as is often required when laying stormwater pipes.
The stormwater drain will significantly reduce flooding in and around the Green Square area and particularly at Joynton Avenue and on Botany Rd, Zetland.
Much of the route from Link Rd to Alexandra Canal runs through or under property owned by the City. The route was chosen to minimise the impact on residents, businesses and the environment.
The Green Square Stormwater Drain Project is being delivered by the DG Alliance, a team consisting of Sydney Water, the City of Sydney, UGL Engineering, Seymour Whyte Constructions, Parsons Brinckerhoff Australia and RPS Manidis Roberts.
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