$80 million gets washed out to sea in Sydney’s massive stormwater drain

An archive photograph from the NSW State Library shows people crossing a flooded street in Alexandria. Photo: Supplied Water surges through the area: The big wet that’s all about to change thanks to a massive new drain. Photo: Supplied
Nanjing Night Net

The dream of a grand canal connecting Botany Bay with Circular Quay has gone down the drain – an $80 million stormwater drain that will prevent the new town of Green Square from being flooded. Ever since the area was settled nearly 200 years ago, residents of Alexandria and Zetland have battled floods that regularly occurred on the low-lying swampland only 4 kilometres south of Town Hall. Early residents complained of the threat of typhus as rising waters washed cesspits into farms and homes.  It was the grand vision of 19th century city planners that Alexandra Canal, which funnels 48 per cent of the city’s stormwater out to Botany Bay, would be extended to create a grand waterway from Botany Bay to Sydney Harbour that would also alleviate the area’s perennial flooding.  Now that dream is being realised, but not quite in the way those early planners imagined. A massive, 2.4 kilometre underground stormwater drain costing a reported $80 million, which will connect with the Alexandra Canal, will finally be built. To prevent floods costing lives in what will soon be a densely populated urban centre, the culvert will be nearly two metres high in some parts. It will be wide enough for two cars to drive side by side in the area where the waters converge as the drain meets the Alexandra Canal.

A range of studies originally considered building detention ponds near the future aquatic centre and close to the Drying Green – named because it was where tanners once dried their hides. But a lethal combination of floods and tides meant they would only make a “marginal difference” in a once-in-100-years flood.

”You need to cope with a flood of over two metres with flowing water. That’s very dangerous,” City of Sydney chief operating officer Kim Woodbury said. Without the new stormwater drain, a bad flood would have caused water to flow down Green Square’s town plaza – where an underground library will be located – and the town centre would have to be built on stilts. “And we wouldn’t have got approval for that,” Mr Woodbury said. The massive drain is a joint project by the City of Sydney with Sydney Water. A review of the stormwater drain’s environmental factors is now on display and requests for proposals have been sought from construction companies. Work is expected to start in March next year. A once-in-100-years flood in 2012 washed cars down Joynton Street, Zetland, resulting in the rescue of 20 passengers. Flood waters spread nearly 500 metres to reach a depth of two metres at their worst. “One car was floating down, then another car came in, and another and another, and they kept coming in,” said Robert McFarland, a State Emergency Service volunteer, who was commended for his bravery that night when he rescued 10 people from six cars.

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