A massive underground tank capable of handling 11,000 toilet flushes a minute is set to transform Launceston’s sewerage system and slash the amount of pollution flowing into the Tamar Estuary.
The $60 million, 10-megalitre facility at Ti Tree Bend has now taken shape, with its concrete walls and floors complete and the lid soon to be installed as part of the ambitious environmental project.
Once up and running, the tank will capture and treat sewer overflows that have historically spilled into the river during heavy rain.
“This won’t just have a great effect on the Tamar Estuary, it will also be enormous for the future of Launceston,” said Infrastructure Minister Kerry Vincent during a site visit.
The facility is expected to cut sewage overflows into the estuary by 60%, preventing around 387 megalitres of combined sewage and stormwater from entering the river each year. Of that, about 34 megalitres is straight sewage.
TasWater’s General Manager of Project Delivery Tony Wilmott said modelling shows the project will make a big dent in pollution levels.
“We’re expecting, through modelling, a 70% reduction in nutrients that enter the waterway each year,” Wilmott said.
The project is a remarkable feat of engineering, with the 60-metre-long, 40-metre-wide and 10-metre-deep concrete tank being built on former swampland that once served as a sewage lagoon.
To stabilise the site, engineers had to mix 28,000 cubic metres of soil down to a depth of seven metres, creating what Wilmott called “a very large concrete block” to keep groundwater at bay during construction.
The structure is anchored by piles driven 18 metres into the soil, designed not only to support the tank’s weight but prevent it from floating, as it sits two metres below the water table.
An equally impressive pipeline feeds the facility, running 45 metres beneath the Tamar River from the Margaret Street pump house.
“The pipeline that goes underneath the river to feed this … is an enormous engineering feat in its own right,” Minister Vincent said.
He said along with tackling current pollution problems, the project is designed with the city’s future in mind.
“An extra 10,000 homes will have the capability of feeding into this system as well as Legana, Prospect and other sewerage treatment plants as they are shut down and directed this way,” he said.
The tank marks the first stage of a broader overhaul of Launceston’s sewerage and stormwater systems, with completion on track for between mid and late September.
