The district council has applied to the Otago Regional Council for resource consents to discharge treated wastewater into the Kawarau arm of Lake Dunstan, to discharge contaminants to air and sludge or biosolids to land from the Cromwell and Bannockburn wastewater treatment and disposal systems.
Following a hearing in Cromwell yesterday, regional councillors Bryan Scott and Louise Croot reserved their decision on the matter.
The district council was granted an interim consent last year to continue to discharge wastewater into the lake but was told by the regional council no further short-term consents would be approved.
Dye-testing of an effluent plume in the Kawarau arm last year highlighted an unacceptable risk to the environment and public health and the district council was forced to find a solution quickly.
Cromwell Community Board chairman, Central Otago deputy mayor and district councillor Neil Gillespie gave evidence about the two short-listed options for upgrading the treatment plant.
One option was an advanced biological treatment system costing $16.7 million ''that would deal with public health and nutrient concerns in one hit'' and would add $543 to each Cromwell ratepayer's annual wastewater rate from 2017.
The second option, costing $9 million, was a staged approach that dealt with public health concerns first and then environmental objectives further down the track.
It would add $253 to each Cromwell ratepayer's annual wastewater rate from 2017.
''It is critical that Cromwell gets it right and does not rush into a solution especially in the current environment of rate-capping and recent annual double-digit rate increases,'' Mr Gillespie said.
''The balance of environmental effects and affordability will be critical.''
Cr Scott said although work was ''not happening as quickly as we would like'', he was pleased to see the district council come up with a time frame for the project.
"I see this as a formal commitment ... it's time to deliver.''
District council infrastructure services manager Jon Kingsford hoped the consent process would be completed by June next year.
Discussions would then be held about sludge removal and disposal options.
Between June 2014 and June 2015, the council would seek designs for the new plant and then it would tender the work.
Construction was likely to begin in mid-2016.
The plant could be in operation by July 2018.
The regional council's resource management director Selva Selvarajah has recommended consent be granted, subject to conditions.
The Cromwell and Districts Community Trust, and John Morton, on behalf of landowners near the wastewater plant, made submissions listing concerns about the disposal of sludge and the impact of discharging wastewater into the lake.
