Light at the end of the tunnel

BREAK THROUGH: Auckland Regional Council chairman Mike Lee, left, Auckland mayor John Banks, MP Rodney Hide and Watercare chief executive Mark Ford don hard hats to watch Project Hobson???s tunnel-boring machine break through into the Logan Terrace shaft.

Relevant offers

The cutting-edge machine that’s been excavating a wastewater tunnel under the Orakei Ridge and Hobson Bay for the past seven months broke through to its destination at the Logan Terrace shaft last week.

The tunnel is part of Watercare’s Project Hobson, a $118 million project to replace the ageing sewer pipe that bisects Hobson Bay.

Watercare chief executive Mark Ford was joined by Local Government Minister Rodney Hide, Auckland mayor John Banks and Auckland Regional Council chairman Mike Lee as the 70-metre tunnel boring machine called Te Kaha, the strength, cut through the final section of its journey.

Watercare project manager Mike Sheffield says about 105,000 tonnes of earth was removed during the excavation of the 3km long, 4.3 metre wide tunnel.

"The amount of earth removed and the 14,550 pre-cast concrete segments used to form the structure illustrate the magnitude of this operation," he says.

The earth-pressure-balance tunnel boring machine, which creates pressure at the bore face to counteract the forces exerted by earth and water underground, was custom made in Canada and had to be assembled underground.

Mr Hide commended Watercare for coming in under budget and ahead of schedule in completing the tunnelling phase of the project.

Mr Banks says he’s proud to be associated with the project, which will reduce stormwater overflows into the harbour and make the eastern beaches cleaner.

Further work will now be undertaken to remove the internal railway line, the electrics and ventilation used during the operation.

In the coming months the noise enclosure will be removed from the Orakei Domain construction site and the temporary shaft filled in.

Construction work on the new Orakei pump station is progressing steadily. Mr Sheffield says it will have six heavy-duty pumps capable of pumping 6000 litres a second.

"Working together they could empty an Olympic-sized swimming pool in just over eight minutes," he says.

Commissioning of the pump station and wastewater tunnel will begin in October and they are expected to be fully operational in December. The project is scheduled to be completed in 2010, after the removal of the old sewer pipe.

- © Fairfax NZ News