"Best bang for the buck" to improve environmental performance was one of the parameters behind changes proposed for the Otematata sewage treatment scheme by the Waitaki District Council.
"As decision-makers, we need to ensure the solutions and conditions imposed on this community are affordable and practicable," the council's assets manager Neil Jorgensen told an Environment Canterbury (ECan) hearings panel in Oamaru yesterday.
The panel of Emma Christmas (chairwoman) and ECan councillor Bronwen Murray was considering a resource consent application for changes to the Otematata scheme to ensure it met environmental standards.
Mr Jorgensen said Otematata had a normal population of 189 people, but 448 ratepayers, the majority owning holiday homes.
The scheme between State Highway 83 and the Otematata boat harbour at the head of Lake Aviemore was built when Otematata was created to build the Benmore dam in the 1960s. It was designed to be easy to manage, maintain and operate.
It was entirely gravity-fed, reducing costs and making it viable long-term. Weighing up ongoing operational costs while mitigating environmental effects and subsequent affordability were key concerns.
Mr Jorgensen said the current disposal to land by spray irrigation failed to adequately deal with environmental issues and breached conditions imposed in the consent issued in 2003. The main issue was ponding of treated effluent in the disposal area, particularly when the ground froze during the winter. The trench disposal system would resolve that and would be an improvement on what was happening now.
Mr Jorgensen encouraged the panel to to take into account the environmental effects versus the size of the community that had to pay for any improvements and ongoing costs.
Environmental engineer Humphrey Archer said the existing system had provided reliable and low-cost treatment.
The proposed upgrading to an infiltration trench would eliminate the potential for ponding on the ground from the present spray irrigation disposal.
The new system would not cause significant adverse effects on Lake Aviemore. It would improve water quality in the Otematata River by reducing emergency discharges from the scheme to it.
The panel also heard an application from the Waitaki council to renew the resource consents for the Kurow sewage treatment plant for another 35 years.
Mr Jorgensen said Kurow had the same problems as Otematata - a small rural community facing costs for its infrastructure, repeating the "best bang for the buck" approach.
Already renewing the sewage plant consent with no changes to the present system had cost the council about $100,000.
The council had looked at alternative sewage treatment systems, but the large capital cost for Kurow residents when compared with environmental gains did not stack up, he said.
The plant, between State Highway 83 and the Waitaki River, has an oxidation pond discharging to a wetland then via seepage to groundwater.
Environmental consultant Tom Heller said investigations showed the treatment plant was having no more than minor effect on groundwater within 50m of the wetland or on surface water within 200m.
Expensive plant modification or upgrades were unlikely to result in any discernible differences on groundwater downstream of the plant, he said.
In both cases, the panel reserved its decisions.
- david.bruce@odt.co.nz .nz
