Hunua 4 Watermain

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The Hunua project is the biggest water pipeline project undertaken in New Zealand for many years and involves 30 kilometres of 1.3 to 1.9 metre diameter steel pipeline traversing Manukau and Auckland cities. It involves the crossing of Manukau Harbour, three motorways, three railway lines, a creek and eight streams.

GHD was engaged in 2005 to carry out an options study for a new watermain from ‘southern sources’ to ‘city centre’.  As a result of a competitive tender, GHD was jointly awarded the design contract in strategic partnership with engineering consultancy CH2M Beca in 2008. GHD services include:

  • Overall project coordination and management of options study
  • Preliminary planning and environmental assessment of multiple route options
  • Options feasibility investigation
  • Issues, options and constraints evaluation (environmental, social, economic and cultural)
  • Consenting strategy and stakeholder management and coordination of specialists for AEE and consenting applications
  • Consenting within existing and proposed urban residential, commercial environments, rural, open space, coastal waterways, scheduled heritage sites, protected vegetation & ecological habitats
  • Stakeholder and public consultation assistance
  • Pipe materials study, valves and other equipment selection
  • Survey, constraints mapping and reporting (GIS)
  • Concept and detailed design of large diameter bulk watermain
  • Cathodic protection design
  • Construction methodology development including Trenchless methods
  • Cost estimation and quadruple bottom line reporting
  • Risk management
  • Procurement strategy development and procurement management
  • Tender, construction supervision, contract administration, testing and commissioning

In the early stages, GHD’s planning, hydraulic, environmental and geotechnical engineering specialists developed preferred options involving key stakeholders. It was essential that this process bring these stakeholders along for the journey, taking into account the quadruple bottom line approach to delivery and positive community and stakeholder outcomes. GHD delivered an options report to Watercare in 2007 evaluating 50 proposed routes for the watermain. Initially a total of six options for meeting project objectives were provided to Watercare.

GHD initiated the consultation from the options development phase through to consenting in 2009.  They prepared consultation material and liaised directly with three consenting authorities, NZHPT, ONTRACK, NZTA, iwi and other interested community groups affected by the project. A holistic project approach and commitment from the GHD team provided a streamlined and ‘consentable’ option which minimised the impacts on the environment.

In late 2008, GHD and Beca started the detailed design, consultation and consenting phase and successfully completed consultation strategies and action plans that supported the RMA process. Through identifying these areas early and addressing them via a constraints evaluation process, the GHD team further refined the route alignment and construction of the pipeline to address sensitive coastal environments.  They worked in the vicinity of Auckland International Airport, NZTA state highway designations (1 & 20), scheduled heritage sites and sites of cultural significance to iwi.

The Hunua 4 pipeline will run through the heart of the city and a construction corridor will run past the front doors of approximately 5000 properties.  There were a number of challenges including:

  • Producing design options that could be successfully defended at hearing
  • Ground conditions that varied from soft peats to hard basalts
  • The minimisation of traffic disruptions and environmental effects
  • The integration of Hunua 4 with existing reticulation
  • The identification and protection of other services
  • The design of Hunua 4 to allow future roading upgrades
  • The establishment of clear lines of communication to ensure everyone affected by the project was fully informed

First stage construction, the section incorporated in new Manukau Harbour Bridge, started in October 2009 and was completed in July 2010. Preliminary design of the remaining route was delivered in Nov 2009 and detailed design is now underway. Notice of Requirement (NOR) and Resource Consent applications were lodged in March 2010.  Affected parties were notified in May 2010. The Hearing was held in August 2010. A crucial connection to Hunua 3 in Onehunga is programmed for June 2011.

The main construction contract(s) is programmed to start in early 2012 and final commissioning is expected in 2016.

When completed, this project will substantially improve security of water supply to the city’s 1.3 million people. The lifetime of the Hunua 4 watermain is estimated to exceed 100 years, and its functionality, design and structural integrity is of significant importance to Auckland and New Zealand.



As the world’s population grows and our standards of living improve so does our need to manage the water in our environment. We need to maximise its application for human well-being and minimise impact on the environment. GHD engineers, scientists and planners can provide sustainable, cost-effective and innovative water solutions.  We assist water utilities and others who provide water services to optimise infrastructure and adapt to environmental changes in ways that balance the needs of our communities. And we enable clients to meet compliance, improve profitability and maintain their commitment to sustainability.

GHD continually expands the boundaries by engaging in research, enhancing existing systems and strategies, evaluating new procedures and transferring technology from other industries into the water industry. We work with our clients through all project stages planning, investigation, design, delivery, operation and renewal.

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