National stocktake of municipal wastewater treatment plants and cost estimates for upgrading wastewater treatment plants that discharge to the ocean.

These are two of four reports commissioned by the Department of Internal Affairs as part of the Three Waters Review, which DIA is undertaking to gain a better understanding of the challenges facing three water services in New Zealand and to improve the regulation and supply arrangements for three waters (drinking water, wastewater and stormwater) following the Havelock North campylobacter outbreak in 2016. The reports give a national-level assessment of the state of New Zealand’s local authority wastewater services.

Sharon Dines led the preparation of the wastewater treatment plant stocktake report. Dr Ian Boothroyd and Dr Sharon de Luca provided technical expert input into the cost estimates report.



Worked with

The Catalyst Group
The Wastewater Specialists

Project date


National Stocktake of Municipal Wastewater Treatment Plants

This report provides a national-level stocktake of the regulation of municipal wastewater treatment plants (WWTPs) by regional councils. In particular, the stocktake provides an assessment of resource consents and relevant plan rules in place for the primary discharges from municipal WWTPs, and the compliance, monitoring, enforcement arrangements and practices for these consents and rules.

The stocktake was conducted by GHD and Boffa Miskell and the regulatory aspects of this report were peer reviewed by Dr Marie Doole, The Catalyst Group.

Some key trends are evident in the data collected with the following implications:

  • WWTPs require resource consent as a discretionary activity in most regions.
  • More than half of the existing municipal WWTPs in New Zealand require consenting currently, or in the next 10 years. This will result in significant costs for territorial authorities who already have multiple priorities including meeting more stringent water quality standards and responding to climate change.
  • Parameters monitored in the discharges from WWTPs and the limits placed on discharges are highly variable, with little consistency apparent both within many regions or nationally. There is no relationship between contaminant monitoring and receiving environment, type of plant, or age of consent. In effect, conditions on WWTPs appear to be set in a piecemeal way without systematic regulation, differing widely from plant to plant. Although some councils are making some progress in this area, consent conditions could be standardised to provide greater consistency within and between regions and across the country, to enable meaningful comparison with water quality attributes and national bottom lines in the NPS-FW and to improve compliance and enforceability.
  • Monitoring, reporting, compliance grading systems and enforcement systems could be standardised to provide greater consistency within and between regions and across the country.
  • The high levels of variability in regulation of WWTPs mean that benchmarking, performance comparison, or national reporting is not likely to be possible under current arrangements. Compliance, monitoring and enforcement is likely to be resource-heavy and unduly complicated for both regulators and owner councils. Reconsenting is also likely to be difficult, with each community engaging in reconsenting from scratch with no national standard or guideline to structure consultation.
  • The consulting team consider that consistency in monitoring and reporting will improve the ability to obtain a clear, detailed and accurate national stocktake of WWTP performance and is likely to result in streamlining and simplification of systems and therefore cost savings. It also has the potential to make community engagement significantly easier on reconsenting.

Cost Estimates for Upgrading Wastewater Treatment Plants that Discharge to the Ocean

GHD Limited and Boffa Miskell were engaged by DIA to provide a national level cost estimate for the potential upgrade of municipal WWTPs that discharge to the ocean in New Zealand if national minimum discharge standards for key contaminants are imposed. The Wastewater Specialists (TWWS) provided technical support and localised knowledge of WWTP operation around New Zealand.

A literature review of standards applied internationally was undertaken. Minimum discharge standards are a common feature of many overseas jurisdictions, including the European Union, Canada, USA, and Australian states. Based on this review, and taking into consideration the New Zealand coastal environment, relevant regulatory settings (including the National Policy Statement for Freshwater Management) and local infrastructure, three categories of minimum standards were developed.

The findings of the study are that 48 WWTPs would require upgrades to meet the proposed minimum standards. The total capital investment to achieve this target is estimates to be between $1.1 and $1.5 Billion, with an annualised cost of $73 to $110 Million.

Our role was to prepare the Report and provide technical advisory services.