Effluent consent granted, but growth capacity a concern

The Otematata sewage treatment plant will have to be better managed by the Waitaki District Council under a new resource consent issued by Environment Canterbury, after problems with disposing of effluent.

The council applied for a new consent, which has been granted for 28 years to replace the previous one, because it wanted to change the way treated effluent was disposed of.

The application was heard by an Environment Canterbury (ECan) hearings panel of Emma Christmas (chairwoman) and former ECan councillor Bronwen Murray in Oamaru on April 8.

However, while approving the consent, the panel expressed doubts about whether the new system would be able to cope with the growth of Otematata.

Otematata had a permanent population of 189 people, but 448 ratepayers, the majority of whom owned holiday homes.

The scheme, between State Highway 83 and the Otematata boat harbour at the head of Lake Aviemore, was built in the 1960s when Otematata was created for Benmore dam workers. It was designed to be easy to manage, maintain and operate.

However, the present disposal system of spraying treated effluent on land was not successful, leading to breaches in conditions imposed in the resource consent.

Discharges were greater than expected, effluent ponded throughout the year, aggravated by frozen ground in winter, and there had been problems with the ultraviolet treatment unit.

When effluent could not be disposed of, it went to the Otematata River.

The council proposed to change the disposal system from spraying to soak trenches. Perforated pipes would be buried in trenches for the treated effluent to flow into the ground.

It also wanted the volume of the discharge to be increased.

However, the panel was not happy with evidence produced by the council during the hearing, particularly regarding existing volumes and future growth. It asked for further information after the hearing was completed.

The amended trench design by the council was likely to meet the peak demand in summer, when holiday-makers were in Otematata, next year, but there was little leeway for future growth.

The panel doubted the council would not breach conditions of the consent or allow spills into the Otematata River.

"We are therefore cautious of accepting assurances provided by the applicant," the panel said.

Despite that, the panel decided to grant the consent, but has imposed additional conditions to cover its concerns.

- david.bruce@odt.co.nz

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