What is being done about wet weather overflows from the network?

In the last three to four years, work has focused on addressing the big challenge of wastewater overflows into the harbour during storms.

Wellington Water has been replacing and repairing many valves, pumps, pipework and electrical components to get the sites working as they were originally designed.

In particular, upgrades to Porirua’s wastewater pump stations are having a large impact at low cost.

Is closure of Titahi Bay beach during heavy rain attributed to the present capacity issues of the treatment plan?

Health warning signs are placed at Titahi Bay after wet weather bypass events and the occasional operational issues with the treatment plant on a precautionary basis – the Bay is not closed but the health risk is higher.  The Wastewater Treatment Plant capacity limitations are currently being rectified and by the end of 2020 it is expected that the plant will have an operational capacity which is more than sufficient to fully treat all wastewater which can be delivered to it. 

In parallel, Porirua City Council and Wellington Water will be investigating how to reduce the adverse effects of stormwater on water quality at Titahi Bay and elsewhere in the city.  That will be a long term issue to resolve and our general advice is that it is not safe to swim for 48 hours after heavy rain anywhere in the Wellington urban area.

Is cross contamination of stormwater and wastewater an issue and will it be investigated and resolved as part of this project?

Yes, this is an issue particularly in the wider network and is contributing to many of the overflows.  That is why we are proposing a network-wide improvement plan and looking at developing a programme of inspections and investigations to reduce ‘inflow and infiltration’. We will also continue to enforce rules around the connection of stormwater pipes to wastewater, which is an ongoing issue.

How are you going to reduce discharges into waterways and the harbour?

We’re investigating the development of increased storage and/or conveyance capacity at key points in the wastewater network as well as the capacity of the treatment plant are key components of improving the wastewater system.

This will help reduce overflows of wastewater from the network as well as managing the flow of water to the treatment plant.

The programme will also work to prevent cross-contamination of stormwater and wastewater, which is currently contributing to overflows.

What is the added capacity to the network and treatment plant going to be - is it future proofed?

Future urban and population growth in Porirua and Wellington City is a fundamental driver for focusing improvements on the wastewater network. The treatment plant itself is highly effective, and recent upgrades have ensured it can meet current flows.

However, we are proposing further capacity upgrades as part of replacing the current discharge consents, which expire in October 2020. This will ensure the treatment plant has ample capacity for projected growth out to 2060.

The other critical component is managing flows of wastewater from the network to the plant during major wet weather events. That is why our focus will not only improve capacity of the plant but enable flow control.

Where are things at with the project?

  1. We are currently assessing nine different options for re-consenting the wastewater treatment plant, which include an integrated long-term improvement programme for the wastewater network. These are being evaluated based on a range of factors including effectiveness, feasibility, constructability, cultural and social impacts and cost.
  2. We expect to present a preferred option to PCC and WCC in August 2019 and if approved, will lodge the consent application with Greater Wellington Regional Council in March 2020.  The regional council will manage any public consultation process after this point
  3. We also expect to seek consents for the wet weather overflows and dry weather leakages in 2020, which are not currently consented and need to be as part of managing and reducing them.

What can I do to help?

  • Check to ensure roof down pipes aren’t connected to gully traps
  • Ensure gully traps are suitably elevated and protected from the over land flow of stormwater on your property
  • Keep trees clear of your private wastewater laterals
  • Don’t flush wet wipes, paper towels, sanitary products which can clog the system and exacerbate overflows
  • Consider purchasing water saving technologies when replacing washing machines, dishwashers, toilets, showers and taps
  • Consider composting food waste rather than using or installing a food waste disposal unit.

Find out more about how you can make a difference in looking after wastewater here