Costs are rising and deadlines slipping as the Dunedin City Council continues work on the stage two upgrade of the Tahuna wastewater treatment plant.
Dunedin City Council Tahuna upgrade project manager Brian Turner last week said the cost of the project had risen by at least $2.2 million, from $73.8 million to "about $76 million".
However, the project remained "on budget" despite the increase, as the completion cost was expected to rise with inflation and had been factored into the long-term council community plan, he said.
"It's going up because of inflation from year to year."
Design delays also meant the project was "a couple of months" behind schedule.
"It's just taken time to design changes that we want. There's been a lot of work. We do need to try and make up some of that time if we can. There's various ways of doing that," he said.
One way might be to increase the workforce when construction of the stage two facilities began, although that would need to be discussed with the contractor - and with an eye on the budget.
"One of the constraints will be not to put the price up."
The stage two upgrade aimed to improve the quality of wastewater treatment at the plant, and the processing of solid materials generated by the wastewater treatment process.
It required the use of new ultraviolet light disinfection, digestion systems and drying techniques, and followed the completion last year of a $37 million, 1.1km outfall pipe at Tahuna.
The stage two upgrade had been expected to cost $67.2 million before steady budget increases, but annual operating costs were expected to be offset by using captured methane from the plant's processes as an alternative energy source.
Councillors this year voted to defer spending on the solids side of the project for two years, while consideration was given to options for dealing with the sludge generated.
Work on the wastewater side of the project was still in the design phase, but that process was "largely completed".
A short-list of potential contractors were preparing prices, and tenders were expected to be received, and a decision made, by the end of September, Mr Turner said.
