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Dolphins jumping Bottlenose dolphin swimming with young

Whangarei wastewater masterplan, New Zealand

Whangarei District Council entrusted us to help improve the health of Whangarei Harbour – one of New Zealand’s ecological treasures. We provided a range of strategy, design and advisory services. Praise has been given for the improvement of the harbour's water quality as evidenced by the return of dolphins after many years.

Finally the dolphins that are frequenting our harbour are not being harmed by our pollution

Ingrid Visser (Northern Advocate, 16 August 2013)

Marine mammal expert, Ingrid Visser, has commended Whangarei District Council for its new wastewater treatment process, which has eliminated the largest pathogen source entering the harbour. "Finally the dolphins that are frequenting our harbour are not being harmed by our pollution," (Northern Advocate, 16 August 2013).


Decades of under investment resulted in a wastewater network that overflowed frequently and a treatment plant that could not meet its effluent quality targets. Our role involved improving the wastewater system’s performance by providing wastewater flow monitoring, hydraulic modelling, a 10-year capital works programme and master plan as well as the design of a peak flow treatment system. We also covered resource consents and an assessments of environmental effects to help implement the works.


We implemented projects which achieved the council’s objectives at a tenth of the cost initially projected. Early on in the hydraulic modelling process it was found that at least NZD$200 million of investment in the network would be required to reduce overflows to an acceptable frequency. Further refinement and the implementation of storage and treated overflow sites reduced the capital works to approximately NZD$20 million. We're continuing to provide process optimisation support for the treatment plant to enhance effluent quality of existing assets.

The project's findings demonstrate the value of detailed analysis, leveraging the power of data to provide results that make a real-world difference.


  • Long-term flow monitoring, data analysis and hydraulic modelling optimised the network upgrade strategy saving the client over NZD$180 million. Ongoing flow monitoring is providing data to verify the actual improvements in the network as various upgrades are completed, providing confidence in the overall strategy.
  • Integrating the network and treatment plant strategies targeted the issues providing quick results and minimal cost.
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