Progress on reducing pollution in Titahi Bay

Published 26/05/2020

Here's a look at the programme of work underway to improve Porirua’s wastewater network, that will help reduce pollution on the coast at Titahi Bay and in the Harbour.

Wastewater treatment plant consent application

Porirua City Council is in the process of seeking a consent to continue operating the wastewater treatment plant for the next 20 years, as set out here.

There will be an opportunity for people to comment later this year. The new consent will have different rules/requirements from the current one. The consent application is based on 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.

The treatment plant generally treats wastewater to higher than the required standard, and the discharge from the plant has been scientifically assessed to be appropriate for the location.

Overflows and bypass

The current consent recognises that from time to time there will be a need to discharge some partially treated (screened) sewage along with the fully treated wastewater, in particular when there is heavy rainfall and volumes are above the capacity of the treatment plant.  As the city has grown, the frequency of these discharges has increased. The next planned upgrades will address this issue.

We acknowledge the need to invest in upgrading the wastewater and stormwater infrastructure that serves the community.

Find out more about our plans here.

 

Titahi Bay is still closed to swimmers

Unfortunately, Titahi Bay is still closed to swimmers because of contamination.  This is not from the treatment plant.  It is because of cross-contamination where wastewater (sewage) accidentally gets into the stormwater pipes, and then directly into the Bay. In particular, our information points to the South Access stormwater culvert at the south end of Titahi Bay Beach.

We have identified, through data collection, three particular areas of concern, including an 8 metre section of collapsed pipe, which we know are contributing to this contamination. We are working hard to fix these faults and will keep the community advised of progress.

We will keep warning signs in place at Titahi Bay as a precaution while this work continues.

Monitoring and measuring

We are regularly monitoring and measuring water quality at Titahi Bay (and other points around the coast and in the harbour).

There are two testing programmes underway.

To assess whether Titahi Bay is safe for swimming, independent contractors take measurements  as part of the Greater Wellington Regional Council regional bathing site sampling programme (which we call Baywatch). These samples are correctly taken knee-deep in the sea (0.15 metres from the surface).  We have also been sampling at the outlet of the South Beach Access Culvert.

In addition, there is a separate testing programme required by the treatment plant consent, that monitors the discharge from the plant.  These samples are collected and analysed by an independent lab to the satisfaction of the regulator, Greater Wellington Regional Council.

It is incorrect to say data is biased or sanitised. 

The results from both testing programmes reinforce our assessment that the contamination at Titahi Bay is coming from the pipe network, not the plant.

If you have questions please contact Poriruawastewater@wellingtonwater.co.nz