The Wastewater System

The Porirua wastewater system is made up of a large network of pipes and pumping stations that feed into the treatment plant.

The network

  • 573 kilometres of pipes and 54 pumping stations
  • Covers 180 square kilometres of catchment across Porirua city and north Wellington suburbs Newlands, Johnsonville and Tawa
  • Feeds 300 litres per second every day into the wastewater treatment plant at Titahi Bay, Porirua.

The treatment plant

  • Capacity to treat 1,100 litres of wastewater per second
  • Ongoing upgrades over the last six years have enhanced the plant's capacity. Within the next couple of years the capacity of the plant will be 1,500 litres per second, more than enough to cater for the current wastewater flows to the plant
  • Improved quality of discharge, keeping the coastal shores cleaner and safer.

For a visual representation of the network and treatment plant, view the public information posters here

The issues

Wet weather overflows from the network into streams and the harbour are one of the biggest issues. These overflows are exacerbated by inflow of stormwater into the network.

During normal flows the treatment plant performs well and produces high quality treated wastewater.   However, overflows can occur during very heavy rainfall events when flows from the network exceed its capacity. To address this existing issue, upgrades have been undertaken over the last six years and are on-going.  These will be completed in the next couple of years and will ensure that the plant can fully treat all the wastewater which is delivered from the network.  

Read more about how we plan to address these issues.