Tamar estuary milestone reached as final section of sewage pipeline goes in

The three-kilometre-long, one-metre-wide pipeline will increase the capacity to transfer sewage and storm-water, travelling 40 metres under the riverbed of the Tamar River.

TasWater general manager Tony Willmott said the pipeline would ensure that 387 mega-litres of sewage and storm water during rainfall events did not make its way into the waterway.

"That's 34 mega-litres of sewerage, which is straight from the network, that will now make its way to Ti-Tree Bend [sewage treatment plant] to be treated prior to being discharged to the river," Mr Willmott said.

"It's a fantastic outcome for the river.

"We've had 18 local contractors involved, along with pipeline drillers from Queensland who have brought their specialist equipment into the state to undertake this job for us."

Mr Willmott said the finishing touches were being put in place ahead of the pull-through of the last section of the new pipeline.

It will connect the Margaret Street Pump Station with the Ti-Tree Bend Sewage Treatment Plant.

"The pipeline runs as far below the riverbed as the Silos Hotel is tall, and working this deep underground makes this job one of the most complex we've ever undertaken," Mr Willmott said.

Infrastructure Minister Michael Ferguson said the health of the community and environment depended on the health of the river itself.

"That's what this project is really all about - the collaboration between the [three] levels of government under the 2019 Launceston City deal has enabled these milestones to be achieved," Mr Ferguson said.

"This is a wonderful part of the delivery - it'll mean a healthier river, a safer river and it means of course jobs during construction."

Labor Senator for Tasmania Helen Polley said the issues around water and sewerage had been an issue for decades.

"It is essential that we invest in this infrastructure because water and sewerage is the primary benefit to ratepayers and taxpayers everywhere," Ms Polley said.

"As always, it's really important that we demonstrate how effective we can be when the three tiers of government work together to deliver a project like this."