The University of New South Wales (UNSW) and surrounding areas in Sydney will soon have access to additional water with the expansion of the university’s rainwater capture project and the installation of a second percolation chamber below the Kensington campus.

The additional pit will help drain stormwater from 90 per cent of the campus into the Botany Sands Aquifer which lies beneath the university.

As well as replenishing the aquifer, which is used as an additional water supply by local residents and industry, the percolation system takes pressure off Kensington’s stormwater pipes by channelling the water into the aquifer rather than the council’s stormwater system.

The original stormwater retention chamber was installed in 2007 under the Village Green oval and is one of Sydney’s largest percolation pits. The second chamber built near UNSW’s Roundhouse venue will take advantage of stormwater flows which are not captured by the system under the Village Green.

The estimated collected stormwater per year is equivalent to 20 Olympic swimming pools. Bore water is then extracted from the aquifer and reused to supply 43 per cent of the total campus water demand. Claude Pelosi, UNSW Engineering Services Senior Manager, said, “This system is a win for water sustainability, the environment, and the university’s bottom line.”

“Instead of using drinking water to flush our toilets, we substitute bore water in as many contexts as possible. This includes the university pool which is 100 per cent treated bore water, toilets, all irrigation, laboratory uses and air-conditioning.”

The changes to water usage and conservation on the Kensington campus over the past eleven years have seen a 45 per cent drop in consumption of potable water which is assisted with other water saving initiatives like low flow taps, low flush toilets and use of water efficient cooling towers. This is despite a ten per cent building growth on the site.

Mr Pelosi said that by returning water to the aquifer, UNSW is essentially using it as a giant rainwater tank.

“With over 60,000 students and 6000 staff, the university is like a small city. With a larger percolation system, we’re able to capture more rainwater, replenish the aquifer and reduce pressure on the region’s drinking water resources,” Mr Pelosi said.

William Syddall, UNSW Environmental Sustainability Senior Manager, said, “UNSW has an important role to play in not only researching and teaching about sustainability issues but demonstrating sound practices on our campuses. The expansion of our landmark aquifer recharge project allows UNSW to further reduce potable water usage despite an increase in student numbers and total building area.”

The new chamber will be 30m long, 10m wide and 4m deep. It will increase rainwater capture by 20 per cent compared to the original pit built in 2007. A milk-crate-like structure is used to create an empty space where stormwater is collected. The water is then allowed to seep slowly through the sandy soil and into the aquifer.

In a year of normal rain, the system would return 30mL of stormwater to the aquifer. The new tank will be operational in early 2019. 

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