Treatment plant

Future-proofing the treatment plant

Work is underway on upgrading and increasing the capacity of the treatment plant, so it is fit for purpose for a growing population.

In May/June 2021, residents have the chance to have their say on plans to upgrade and operate the Porirua Wastewater Treatment Plant over the next 20 years, by making a submission on a resource consent application. 

Wellington Water outlined the application and the process at a public meeting in Titahi Bay on 9 June 2021. You can see the Wastewater Treatment Plan Community Presentation here. 

Resource consent required

  • Under New Zealand law (the Resource Management Act), special permission is required to discharge treated wastewater.  This permission takes the form of a resource consent, issued by a regional council.  The consent can include conditions that require steps to be taken to minimise the impact of the discharge, and to monitor and report on the impact.
  • The current consent for the Porirua wastewater treatment plant (WWTP) expired last year (2020) and needs to be replaced.
  • Prior to the expiry of this consent, Porirua City Council (PCC) applied to Greater Wellington Regional Council for a new consent (a coastal permit) to discharge treated wastewater from the Porirua WWTP to coastal waters off Rukutane Point. This application is now being publicly notified and submissions sought from the community.

 About the application

  • The Resource Consent application seeks permission to discharge wastewater that has been treated and disinfected to a high standard, through the existing outfall at Rukutane Point, for the next 20 years. Find out more about how the wastewater treatment process works here
  • The application proposes regular monitoring and measurement of the impact, including a new ecological survey and a full review of operations after 10 years.
  • The consent application sets out plans to increase the capacity of the plant, so that it can manage a maximum peak daily discharge volume of 129,600 cubic metres per day, which equates to 1,500 l/s operating continuously for 24 hours.
  • This capacity has been designed to cover projected population growth over the next 20 years. The estimated population in 2018 within the WWTP catchment was 84,000. The population planned for in 2043 within the WWTP catchment is 121,000.
  • Capacity upgrades of the treatment plant will be completed by 30 June 2023. Until then, there will continue to be intermittent, partially treated discharges during heavy rain events .
  • Porirua City Council, Wellington Water and Ngāti Toa are working together to ensure mana whenua are at the table in future decision making on the plant.
  • These plans build on upgrades over the last 10 years, which have seen the quality of the discharge improve considerably.

About the submission process

  • Greater Wellington Regional Council is inviting submissions on the application before 30 June 2021.
  • A submission is the way GWRC can take into account any views, comments or concerns about someone's resource consent application. Submissions can support or oppose the whole application, or support parts and oppose other parts.
  • The executive summary of the application is available here.
  • Copies of the application and information about how to make a submission are available on the GWRC website
  • GWRC will contact submitters about pre-hearing meetings and hearings.

Upgrading the plant and increasing capacity

In 2021, new ultra-violet (UV) disinfection equipment is being installed at the treatment plant to increase the volume of wastewater that can be disinfected. UV light disinfection is the final stage in treating wastewater after solids and the vast majority of harmful bacteria have been removed. It destroys remaining bacteria and viruses before the fully treated liquid is discharged to the sea.

The next step is hydraulic upgrade work, planned for the summer of 2021-22.