We designed and constructed the final section of Auckland's biggest water pipeline project, re-routing the pipeline to minimise impacts, and completing New Zealand's longest ever pipe-jack.

The 32 km long Hūnua 4 project connects Watercare’s reservoirs in Manukau to central city water storage, improving the capacity and the resilience of the city's water network. 

Our project, which was Section 11, involved the design and construction of 3.5 km of the new watermain from Market Road in Epsom to Khyber Pass in Grafton.

The original route of the pipeline was in amongst residential properties, major arterial roads, schools and businesses. Difficult geotechnical conditions, ranging from very hard basalt to soft clays, created further challenges.

We proposed an alternative alignment that re-routed the pipeline along Manukau Road and under the Southern Motorway (SH1), moving construction away from residential areas and avoiding sensitive ecological and heritage sites. The new alignment ensured the project work didn't conflict with construction on the City Rail Link, which was underway in Eden Terrace.

We also developed state-of-the-art trenchless technologies to install the pipe almost entirely below and within the road or motorway corridor, which will dramatically reduced impacts on local residents, businesses and traffic.

We used a tunnel boring machine (TBM) to drive and install 2500 mm ID jacking pipes between six shafts, before lining the tunnel with a 1575 mm OD steel pipe. The pipe-jacks are the longest ever completed in New Zealand.

Close relationships with our design consultants was key to developing and delivering our innovative solution. We worked with McMillen Jacobs Associates to develop the permanent works design and prepare an Assessment of Environmental Effects report to secure resource consent for the project.

Close engagement with the community, businesses, residents, local schools, mana whenua, Auckland Council and Auckland Transport was an integral part of successfully delivering this project in what is a highly-visible, constrained urban environment.

We completed the project on time.