Hunua 4 Section 11 Watermain Finishes First Drive in Auckland, New Zealand

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Project Update by Victor Romero, PE, CPEng

Watercare and McConnell Dowell’s Tunnel Boring Machine (TBM) “Amiria” broke through the Burleigh Street shaft wall and completed its first drive under Khyber Pass Road. The drive from Khyber Pass to Burleigh Street is the shortest of the project at 390-meters-long (1,280 ft) and took six weeks to finish. Working in a confined inner-city site and contending with Auckland traffic, the team pipejacked up to 95 meters (312 ft) a week, finishing the first drive a week ahead of schedule.

This is the first of three drives for this 3-meter-diameter (9.8 ft) slurry TBM that is being advanced by jacking a concrete pipe, which will accommodate a steel pressure pipe installed in a second pass with annular backfill. Amiria will now be fitted with a new power system, rock cutter head, and new computers, before beginning the technically challenging 1.2-kilometer (3,940 ft) drive through the basalt under the Southern Motorway.

The final excavation will be a 1.3-kilometer (4,265 ft) drive under Manukau Road. The tunnel geology primarily consists of basalt, volcanic tuff/tephra, and alluvium. A total of five shafts are being utilized for the tunnel construction.

The project combines traditional cut-and-cover methods with trenchless tunnelling to install the 3.6-kilometer (2.2 miles) long, 1.6-meter (5.2 ft) diameter steel pipeline. A total of nine valve chambers for flow control/isolation and air relief will also be constructed.

The completion of the new watermain will ensure that Watercare can continue to provide uninterrupted, high-quality water as Auckland grows. McConnell Dowell and its permanent works designer McMillen Jacobs Associates are proudly delivering this design-and-construct project to Watercare.