Minimum $9m for sewerage system

MASTERTON'S new sewage treatment system will cost a minimum of $9 million to build, or double that if the most expensive of four remaining options is finally decided on.
Acting on the recommendations of experts, the council has scrapped 10 options for its Homebush site, being mostly hi-tech ones involving such things as ultraviolet disinfection and chemical clarifiers and running to upwards of $36 million just to install.
Still in the mix are two options that would see the existing oxidation ponds retained and upgraded ? but not lined ? and two that would see new ponds built.
The most expensive remaining option would be new ponds with a wetland area that would discharge its treated waste partly as irrigation on to land and partly into the Ruamahanga River.
That scheme would cost $18.1 million to install.
Lining the existing ponds is a no-go should the council finally settle on an option using the old ponds, as consultants have determined this would cost a further $9 million.
Beca Carter consultant Chris Callander said the depth of the old ponds extends to below the water table, making lining them a difficult and expensive job.
He said in any event, widely touted leakage from the old ponds appears to have a negligible effect on the Ruamahanga River, but further tests to confirm this will be done over summer and before the council has to finally arrive at a decision on what scheme will be accepted.
Next month the council will have narrowed down the four remaining options to one preferred option, which will then go back out to public consultation.
By March a final decision has to be arrived at.
Should the council finally settle on the cheapest upgrade option ? the $9.18 million installation ? then yearly operating and maintenance costs are estimated at $320,000.
The all-up cost over the life of the upgrade, set at 25 years, would then be $13.27 million allowing for inflation.
At a briefing yesterday, Mr Callander told councillors and members of a task group looking at project options that people had a wrong perception of oxidation ponds.
It was widely believed that they were an outdated and old-fashioned method of dealing with waste.
"That's absolutely not true.
"Oxidation ponds remain a recognised and accepted technology for treating sewage and are very good at reducing bacteriological counts."
Mr Callander said the "key driver" behind the upgrade was to improve the quality of water to recreational standards at downstream Wardells Bridge.
He said an option using both the land and the river for disposing of the treated effluent was necessary.
A land-only option would mean the council would need far more land than the 93ha it has already acquired at Homebush.
"To irrigate at a rate of 2mm a day over land you would need 850ha and the cost of buying the land, and development, would be $36 million," he said.