Christchurch City Council lodges variation to discharge consent

25 October 2005

Christchurch City Council has applied for a variation to its current Resource Consent to discharge wastewater into the Estuary.

In its application to Environment Canterbury (ECan), the council is seeking a level of ammonia discharge that its waste treatment plant can meet.

City Water and Waste Manager Mark Christison says the council informed ECan and the Discharge Audit Group earlier this year that it was breaching its ammonia mass loadings in its discharge from the plant into the estuary. Since then it has kept interested parties informed while conducting trials in a bid to reduce ammonia concentrations in the discharge.

The upgraded waste treatment plant has reduced the level of carbon and faecal coliform in the discharge, but none of the previous four upgrades have targeted reducing nutrient levels, including ammonia. Even tighter consent conditions for the plant’s discharge are due to apply from this month.

Ammonia reduction will not be necessary when the new Ocean Outfall is commissioned in 2009 due to high dilution rates that occur at the outfall diffusers about 3km off shore, Mr Christison says.

“Our only option is to apply for a variation to the present Estuary Resource Consent which recognises the plant capabilities,” he says

He says that modifying the plant to meet the present consent would require many millions of ratepayers’ money and would take at least two to three years to build. By that stage the ocean outfall will be close to being commissioned.

“We will continue evaluating our treatment processes in a bid to deliver the best discharge quality achievable within the technology limits of the current treatment plant,” Mr Christison says.

Fish surveys and enhanced sampling programmes will also continue in the estuary. The Council has been working with interested parties in finalising the formats of these testing regimes.

The consent is likely to be publicly notified.

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