Ocean Outfall project reaches milestone

5 September 2006

The Christchurch City Council has awarded New Zealand based company McConnell Dowell Constructors Ltd, the contract for the construction of the City’s ocean outfall pipeline.

Five short-listed tenderers were asked to consider two methods of construction: dig and lay (conventional pipe laying) and micro-tunnelling technology.

McConnell Dowell’s tender winning solution will use micro-tunnelling technology for the landward section of the pipe route - from the oxidation ponds across the estuary and South Brighton Spit, and through the surf zone. This means disruption to the surrounding area will be minimised. Beyond the surf zone, the pipeline will be sunk into a pre-dredged trench.  (see attached for indicative pipeline route)

“This is an outstanding solution. Not only is it the best financially for the City, it is the most environmentally sound and least disruptive solution for the local community and recreational users in the vicinity of the pipeline route,” says Mayor Garry Moore.

“This is a major milestone - we’re at the start of the final, even if long, stage in this massive project. The construction of the ocean outfall pipeline is one of the biggest and most important projects the Council is currently undertaking. Ironically, once it’s completed there will be little to see, yet it’s a project that has real benefits for the community.”  

The total expected cost of the project of $87.224 million is within 4 per cent of the estimated budget (inflation adjusted) of $83.856m.

The Council’s City Water and Waste Unit Manager, Mark Christison says to have tendered costs so close to what was budgeted is an excellent result given the size and complexity of the project and the recent construction market conditions.

McConnell Dowell recently completed the construction of the Waimakariri ocean outfall and currently is building the Clandeboye (near Temuka) and Tahuna (Dunedin) outfalls. Mr Christison says, “The company has a strong track record in this type of work and a sound local knowledge of Pegasus Bay.”

Preparation work, away from the construction area, will start immediately. Construction on-site is expected to start in mid-December at the City’s Wastewater Treatment Plant.

Instead of the city’s treated wastewater being discharged into the Avon-Heathcote Estuary, the underground pipeline will take it from the oxidation ponds to 3km out into Pegasus Bay.

Mr Christison says it is possible that the project would be completed at the end of 2008, nine months ahead of the schedule to meet the Environment Court deadline to remove wastewater discharge from the Estuary of September 2009.

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