Progress in improving health of Porirua waterways

Porirua City Council today formally lodged plans to upgrade and improve the Porirua wastewater treatment plant, taking the next step towards improving the health of Porirua’s coastal waters.

These plans are set out in the council’s application to Greater Wellington Regional Council for consent to continue operating the wastewater treatment plant for the next 20 years.

“The consent application outlines how we propose to increase  the capacity of the plant from 1,000 litres to 1,500 litres of wastewater per second and make other technical improvements, so that the plant is fit for purpose for a growing population,” says Porirua Mayor Anita Baker.

The consent application has been developed for Porirua City Council by Wellington Water in discussion with Ngāti Toa. Community views were also sought late last year.

“We value Ngāti Toa’s contribution as we work towards our shared goal of improving the health of our harbour and coastal areas,” says Mayor Baker.

“We will continue to work in partnership with Ngāti Toa on the future of the wastewater treatment plant and our wider plans to improve the Porirua wastewater network.”

 Ngāti Toa Manager – Resource Management & Communications Naomi Solomon says the iwi looks forward to continuing the work with Wellington Water and Porirua City Council around the matters raised in the Cultural Impact Assessment that forms part of the consent application.

“The ongoing management of wastewater is vital to the health and wellbeing of our waterways, and Ngāti Toa would like to see that this managed in an appropriate way,” says Naomi Solomon.

Greater Wellington Regional Council will hear public submissions, likely later this year, before making decisions.

The consent application outlines plans to invest $5 million in capacity and technical upgrades that will be in place by 2023, which will further improve the quality of the discharge and reduce the number of times there is contamination from high rainfall events.

These plans build on upgrades over the last seven years, which have seen the quality of the discharge improve considerably in recent years.

Alongside plans to improve the treatment plant, Wellington Water, on behalf of Porirua City Council, is also improving the network of wastewater pipes leading to the plant.

“We have made a number of improvements to pumping stations and the network in recent years, and this work continues to be a long-term priority,” says Steve Hutchison Chief Advisor - Wastewater.

Editors note:
The wastewater treatment plant is funded by Porirua and Wellington City residents and Wellington Water is responsible for operating and maintaining it. It’s located near Rukutane Point, just south of Titahi Bay, and treats wastewater from Porirua City and northern Wellington suburbs.

Background information on the consent is attached.

For more details on broader plans for the wastewater network, visit https://www.wellingtonwater.co.nz/pwp/

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) expires later this year (2020) and needs to be replaced.

Porirua City Council (PCC) is applying 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. 

Greater Wellington Regional Council will now review the application  and may seek further information before making it public. It is expected that the regional council will publicise the consent application documents and ask the public for their views in coming months. There will be a public hearing of submissions.

In brief, PCC is asking for permission to discharge wastewater that has been treated and disinfected through the existing outlet at Rukutane Point for the next 20 years. The application proposes regular monitoring and measurement of the impact, including a new ecological survey and a full review of operations after 10 years.

PCC and Wellington Water are continuing to work with Ngāti Toa to develop mitigation measures to adequately address adverse effects on their cultural values. This will be presented at the public hearing. 

For the next three years, there would continue to be intermittent, partially treated discharges during heavy rain events until capacity upgrades of the treatment plant are completed by 30 June 2023.

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 (m³) 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.

Alongside the capacity increase, PCC is investing in new ultra-violet (UV) equipment that will provide a higher level of disinfection and will ensure projected population growth can be adequately disinfected.

The consent application includes an assessment of the effects on

•  Marine ecology
• Public health
• Recreation
• Impacts on Ngāti Toa’s cultural values
• Natural character & landscape
  
  

The application includes specialist reports on each of these topics and how potential adverse effects will be minimised. It proposes a monitor, review and respond approach; that is, if monitoring shows that contamination is above a trigger point, the treatment process would be reviewed and, where necessary, changes would be made.  PCC and Wellington Water are proposing a series of legally binding conditions to give effect to this approach.