Hunua 4

Starting in 2012 Watercare have been installing a new water pipeline called Hunua 4.

This watermain runs from the Redoubt Road Reservoir in Manukau City and will terminate at Khyber Pass in the Central City. CB Civil was engaged as Subcontractor to McConnell Dowell to complete the open trench portion of the Hunua 4 Section 11 Project.  This is the final stage of the over 400-million-dollar infrastructure project.  The completion of the new watermain will ensure that water supply will keep up with demand and provide high quality uninterrupted water to a growing Auckland Super City.

M3 EARTHWORK/CONCRETE

CB Civil excavated, shored and installed 700m of DN1575 watermain.  There were 2 air valves and an off-take scour valve.  Due to the varying ground conditions, two different methods were used for shoring. Up to 4.5m deep trenches, these are conventional aluminium shoring boxes 7m in length and were double stacked and driven king post. The second method was pile and plate with mild steel.  During the excavation process, there was close to 10,000m3 of material excavated and removed from site.

The pipes that are being installed are 12m in length and weigh 8.5T each.  These are concrete-lined mild steel pipes that are primed and double wrapped in a polyken tape.  This insures complete isolation from the in ground material which will ensure longevity of the pipes internal integrity.  The complexities around handling such a large pipe mean that to lift them into the trench requires a dual lift utilising a Hiab mounted truck and the onsite 35T excavator.

TRAFFIC MANAGEMENT

Traffic management was part of our scope and we have some major diversions and closure of level 1 and level two roads.  Along with the numerous residents and stakeholders engaged along the pipe route CB Civil interacted with Auckland Transport, Auckland Council and Watercare.

INNOVATION

CB Civil provided extra crews to work in two areas concurrently, this not only allowed our scope of the works to be completed in a timely manner but also benefit McConnell Dowell getting into areas ahead of programmed dates;  in turn, lessening the disruption to residents, road users and stakeholders.