For the health of the people and the environment, the City Council should start planning to build an ocean outfall for its treated wastewater. That is the opinion of experts who have been looking at the future of the city’s sewage treatment.

Last month City Councillors, reporters and people from interested groups were invited to hear the results of studies done since ECan commissioners released their decisions on the Council’s plan to continue using the Avon- Heathcote Estuary as its wastewater outfall.

That decision – in effect telling the City Council to stop putting its treated wastewater into the Estuary as soon as possible – showed a big gap between what the Council and the commissioners thought was the state of the Estuary.

Two groups of expert scientists were asked to have another look at all the evidence that had been gathered so far and give the Council a second opinion. One group looked at public health issues, the other concentrated on the health of the Estuary environment. At last month’s briefing both groups said the commissioners are probably right – an ocean pipeline is a better longterm solution although they did not share the commissioners’ sense of desperate urgency.

The scientists who examined the Estuary’s health said taking away the wastewater outfall would, over time, result in a big drop in the amount of sea lettuce and other green algae growing there. Sea lettuce is a bother. It smells bad when it rots, is a nuisance to people in the area, and is thought to smother other estuary life.

They also said the Estuary would become a healthier place for fish and other marine life.

The expert group dealing with public health looked at evidence and also took into account new national guidelines for grading water quality. They said the Estuary beaches would improve if the ocean outfall was built, but to really lift their ratings the city would need also to deal with pollution – much of it bird and other animal droppings – being washed into the Estuary by the Avon and Heathcote rivers.

The Council has already approved plans for drastically reducing wet weather sewer overflows over the next five years as one major step to meet the targeted improvements.

It was impossible to say how much the city’s population might grow in the next 20 to 30 years and the best long-term solution was to clean up the wastewater as much as possible and put the outflow into the ocean, the experts said.

Neither team thought the Estuary’s health was in immediate danger. City wastewater had been pumped into it for most of last century and it was likely to be able to stand a few more years until the Council did the planning and building needed to replace its outfall.

Christchurch Mayor Garry Moore said people from the different interest groups had been able to sit in while the scientific groups did their work. It was important, he said, that the decision-making about the wastewater treatment was “open for everyone to see”.

“This is a 100-year issue we’re dealing with,” Mr Moore said. “They don’t come up every day, they’re usually incredibly expensive and we’ve got to get it right. We all have to live with the consequences of this thing.”

One idea behind the Council’s earlier decision to push for a continued Estuary outfall was its belief in sustainable development – the idea that the wastewater could one day be a resource, with the nutrients and water separated out and reused.

Mike Bourke, the Council’s Water and Waste Operations and Maintenance Manager, said building a pipeline to the ocean did not cut off those options forever. For now, however, the technologies were far too expensive.