The Council recently announced its preferred option for wastewater, a 15 year programme which includes:

• Completing the present capacity upgrade of the treatment plant to significantly improve standards of treatment
• Extensive modification of the oxidation ponds
• New, improved disinfection treatment to ensure all parts of the Estuary are safe to swim
• Building a submerged rock filter to discharge treated wastewater to the Estuary.

Liquid wastes manager Walter Lewthwaite says the plan gives the Council the flexibility to adopt new treatment technologies as and when they are proven.

"What the Council is doing is choosing to concentrate its investment in the treatment of the wastewater rather than in the construction of an ocean pipeline, which is an option favoured by some.

“The Council favours developing a treatment system so thorough that how the treated wastewater is discharged becomes a relatively minor consideration. “If the treatment is good enough it will make very little difference whether it is discharged via the Estuary or direct to the ocean in a pipeline.

“With the treatment methods proposed, neither will have a significant impact on the environment," he said.

Creation of an ecological wetland reserve — the “Green Edge” — is also an important part of the plan.

Situated along the west side of the Estuary, this will include restored saltmarsh landscape, habitat for birdlife and the establishment of coastal forest and shrubland.

Feedback on the Council's plans for the future of Christchurch wastewater is needed before 2 October.