The Ocean Outfall is the biggest construction project Christchurch City Council has undertaken.

The $87.2m project will take the city's treated wastewater from the oxidation ponds at the Wastewater Treatment Plant and transport it by underground pipe 3km out into Pegasus Bay instead of discharging it into the Avon-Heathcote Estuary.

The project is on track to be completed by the end of 2008. This is nine months ahead of the Environment Court deadline of September 2009 to cease wastewater discharge into the Estuary.

What's currently happening

The tunnelling machine, known affectionately as Dora the Bora, being used to construct the city’s Ocean Outfall pipeline, has completed the first two sections of the tunnelled 'landward' section of the pipeline.

The first tunnel was completed on 31 August 2007 when she reached the edge of the oxidation ponds at the Christchurch Wastewater Treatment Plant.

At 868 metres, the tunnel from South New Brighton Park and under the Avon-Heathcote Estuary, is the longest of the three tunnels that will be constructed.

The second tunnel, covering a distance of 595m from South New Brighton Park along Jellicoe Street toward the sand dunes, was completed on 21 November 2007.

Work is now underway preparing for the third and final drive from the shaft in the dunes to a point out past the surf zone where the reinforced concrete tunnelled pipeline will be connected to the polyethylene marine pipeline.

The dredge started excavating the trench for the marine pipeline on 19 November, and the first pipe section is expected to be floated around from Lyttelton Harbour and sunk into the trench at the end of November subject to weather.

Three of the seven marine pipestrings have already been assembled at Lyttelton and are stored on the sea-bed at Diamond Harbour ready to be refloated and towed around to the site off South Brighton.