STU Committee to consider report on ocean outfall pipe length and UV

The Christchurch City Council is expected to decide this month on the length of the planned Ocean Outfall pipeline and whether the city’s wastewater treatment system needs to include an artificial ultra-violet (UV) disinfection plant.

A report going to the Sustainable Transport and Utilities (STU) Committee meeting on 13 July, considers the results of a public consultation process held earlier this year, studies of ocean current modelling and ecology, and cost considerations.

Mike Stockwell, the Council’s water and waste manager, says the staff recommendation is for a 3km pipeline and no artificial UV disinfection plant. “We are, however, also recommending that provision be made for an artificial UV plant so it can easily be added at a later date if water quality outcomes change in the future.”

Mr Stockwell says that the recommendation has been made by balancing the technical evidence and the wishes of the community.

“Technically, a 2km pipeline without artificial UV easily meets safe swimming and shellfish gathering standards at the beach. However, community opinion, based on a representative survey of 600 people, favours a 3km pipeline without UV.”

“Participants in the representative survey were required to read the consultation document and represented a cross-section of the city’s residents,” Mr Stockwell says.

Recent results from the treatment plant and oxidation pond upgrades combined with the ocean current modelling are very encouraging. “The ocean current modelling results confirm that a 2km outfall pipeline will easily achieve safe outcomes in the ocean, such as safe to eat shellfish and safe to swim,” says Mr Stockwell.

“It’s important that people understand that work either completed or under way at the Christchurch Wastewater Treatment Plant and throughout the city’s sewerage system is already producing a very high standard of treated wastewater,” Mr Stockwell says.

The Council is expected to make a decision about the pipe length and whether to include a UV plant at its meeting on 29 July.

Background

In 2001, the City Council applied for a 15-year extension to continue to discharge the city's treated wastewater into the Avon-Heathcote Estuary. That application was based on upgrades to the Christchurch Wastewater Treatment Plant.

Following appeals, however, Environment Canterbury said the Estuary discharge could only continue until 2009. The Council needed to find an alternative and, in October 2002, it began preparing an Assessment of Environmental Effects for an Ocean Outfall through a pipeline of no less than 2km.

It is expected that the Ocean Outfall project will be completed around 2009, however this depends on how long the planning and consents process takes.

Pipe route

After considerable consultation with the South Brighton community and advice from independent experts, the City Council on 11 December 2003 approved Jellicoe Street as the pipe route for the Ocean Outfall.

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