06 Mar 2023
New outfall project to see Turriff Lodge Wetland transformed
A new TasWater project beginning in March will see improved environmental outcomes for the Derwent River and the temporary closure of a popular walking area, as the Turriff Lodge Wetland becomes a new park.
The man-made wetland was built in the 1990s as a series of lagoons to provide additional treatment for effluent from the Turriff Lodge Sewage Treatment Plant. The wetland no longer provides any treatment benefit and will only worsen over time, so the area will instead be bypassed using a new underwater outfall. This will remove the effluent from the wetland and enable the area to be remediated.
This project has been discussed for many years, and a process of public consultation by the Derwent Valley Council in late 2020 found community support for the project.
The wetland walking track will be temporarily closed to the public for the duration of the works, from early March until late June 2023.
“We are re-establishing the old Turriff Lodge Sewerage Treatment Plant outfall back into service and making it compliant with modern standards,” TasWater General Manager Project Delivery Tony Willmott said.
“This will be a far superior method of discharging the treated effluent to the poorly performing wetland.”
“New Norfolk is a beautiful and rapidly growing town, and one of TasWater’s priorities is to improve the area’s public health and environmental outcomes.”
The new outfall will extend 14 metres into the river to a depth of six metres and a new diffuser will aid dilution and dispersal. This will improve the local water quality and provide better protections for public health and the local aquatic ecosystem.
Construction of the outfall will involve the use of a boat, divers and a barge for pile driving into the riverbed to anchor the new infrastructure into place. Once the new outfall is diverting effluent away from the wetland, work will start on filling the area. We expect this work to begin in April.
Transforming the wetland will involve removing the reeds and managing the many weeds on the site, as appropriate to each species, then allowing the area to gradually dry and drain, which may create a short-term increase in odour.
Rock, fill and topsoil will be brought in, before seeding the area with grass.
Filling the wetland will be a significant task, with approximately 14,000 cubic metres of fill to be transported to the site from the nearby Bryn Estyn Water Treatment Plant.
“A very small number of trees will need to be removed or pruned for this work to occur, but the vast majority of established trees will be kept in place, so they can continue to provide habitat for birds, be enjoyed by visitors and screen the sewage treatment plant from sight,” Tony said.
“Our environmental assessments have determined this work can be undertaken without risk to threatened species. We’re investing in an environmental management plan that will guide our activity to ensure we can limit our impacts on the local environment.”
“For example, we are taking steps to ensure any platypus in the area maintain uninterrupted access to the river.”
“We understand the importance of this foreshore area for locals and visitors to the Derwent Valley, so all work is being carried out within conditions set by the Environment Protection Authority, the Tasmania Parks and Wildlife Service, and the Derwent Valley Council,” Tony said.