A new sewage pipeline has been installed across Kangaroo Bay, which connects the main sewage line to the Rosny Point Sewage Treatment Plant, replacing the existing undersea concrete and steel pipe constructed in the 1960s.
In February 2018, TasWater brought forward the planned replacement of the old pipe, making it a project of top priority following several breaks which allowed effluent to enter Kangaroo Bay.
During the extensive planning and design stage, TasWater carried out public consultation over the pipeline route including around the Kangaroo Bay foreshore. Overwhelmingly, the community supported the undersea option.
The 350m long pipe has been built out of high density polyethylene, with each 12m length of plastic welded together and connected to 81 equi-spaced concrete blocks, which will anchor the new pipe to the sea bed of Kangaroo Bay.
Constructed at a waterfront facility at Margate it was towed, concrete pads and all, by a tug boat across North West Bay and up the River Derwent to Kangaroo Bay prior to installation.
Buoyed by floatation pipes connected alongside the main pipe, it was positioned to link up to the existing sewer pipes. After the flotation pipes were filled with sea water, it sank and now rests on the bottom of the bay.
The old pipe, however, will largely remain in place as to remove it would disturb too much river floor silt. The old pipe has now become part of the local marine ecosystem of Kangaroo Bay.
Careful investigation has been undertaken to ensure the new pipeline and the concrete anchor blocks will not disturb any of the sea life in the area.
Connection of the new pipe to the existing sewer lines on shore will take place over a period of two weeks when the old undersea pipe is taken out of service.