$200m Tahuna project at an end

Twenty years of work and the spending of $200 million of ratepayers' money was acknowledged yesterday with the official opening of the Tahuna wastewater treatment plant.

The plant's upgrade is the final stage in a 20-year project to improve Dunedin's wastewater system so less waste goes into the ocean and waterways. The project has resulted in the closure of smaller treatment plants around the city that discharged into Otago Harbour and waterways such as the Taieri River.

All wastewater is now sent to upgraded treatment plants at Green Island and Tahuna, where the most money - $97 million - has been spent, upgrading systems and installing further filtering and treatment processes. A further $14.5 million has been allocated for a biosolids project.

Treated water is now discharged at sea via ocean outfalls.

Separated sludge biosolids are disposed of at the Green Island landfill and in future the sludge will probably also be incinerated at the landfill. The upgrades were prompted by the introduction of the Resource Management Act and increasing public awareness of environmental issues in the early 1990s.

Project manager Brian Turner said the work done since the wastewater upgrade strategy was adopted in 1991-92 included new ocean outfalls, buildings, screens, electricity generators, kilometres of new pipes and the installation of modern treatment techniques such as biological trickle filters, wooden biofilters for odour control and ultraviolet treatment equipment at Tahuna.

Contractors handed over the upgraded Tahuna plant to the council in January.

After a testing phase, it was officially opened yesterday with a ribbon-cutting and plaque unveiling ceremony attended by about 50 contractors, staff and councillors.

Opening the plant, Dunedin Mayor Dave Cull said $200 million was a significant investment on the part of Dunedin ratepayers by any measure. He said the project involved dozens of contractors, councillors and staff.

''It's been an enormous, long and expensive effort, but it has been a team effort and it has been handled extremely well.''

Infrastructure services committee chairman Cr Andrew Noone said he had been involved with the upgrade since 1998 and had cut his political teeth on wastewater issues, including sitting through many a discussion and debate, some of which were at times ''testy''.

The strategy had been reviewed several times and adjustments made along the way due to technology or the community or council's desires to ensure it stayed on the best track.

Although dealing with wastewater was not glamorous, having a sustainable treatment process was critically important to the community, he said.

- debbie.porteous@odt.co.nz