June update

Published 09/06/2021

As we head into mid-winter, Porirua City Council and Wellington Water remain focused on reducing the risk of flooding in Plimmerton.

As we head into mid-winter, Porirua City Council and Wellington Water remain focused on reducing the risk of flooding in Plimmerton. We’re up to date with maintenance and have made the maintenance schedule visible on the website (more below).

We’re making sure there’s a pump on standby when heavy rain is forecast and our crews are ready to respond. If you are aware of a stormwater inlet becoming blocked please ring our Contact Centre on 04 237 5089, at any time of day or night.

And we are making progress on developing long-term solutions. 


In recent months we have been taking a much more coordinated approach to how we maintain the existing stormwater assets in the Plimmerton area.

The Plimmerton Flood Action Group requested Council and Wellington Water be more transparent with its maintenance plans and schedules. We agreed this was a good thing to do and we have been working together to pull our information into one place and work out the best way to share this with the community.

There is now a map on the Council's project page that details the maintenance schedule for our assets. This map is a work in progress and we’re very keen to hear from you if we have missed any assets or you think the map could do with any improvements to make it easier to understand.

You can view the maintenance webpage here


The project team is currently doing detailed analysis on options packages – or ‘grab bags’ – that combine actions to reduce the flow and volume of water ponding in Karehana park in heavy rain and get the water out of the park more quickly. 

The analysis includes using a computer model of flooding, which can predict what is likely to happen in different rain events.  The Flood Management and Resilience Working Group (FMRWG) discussed the model in some depth at its last meeting.  While no model is 100 % accurate, the engineers working on this project consider this model a useful tool that will provide helpful information.

The short-list options packages will be assessed against a number of criteria and the FMRWG is providing input into how those criteria are weighted. The short-list of options packages will be shared with the community in July.

Once again, thanks to the Flood Management and Resilience Working Group members Karen Feint, Richard Bradley, Chris Griggs, Kelvin Berryman, Alicja Gear, Grace Alum, Mel Troy, Alan Dodson and Dave Anderson.

They are doing a good job of keeping the project team focused on what’s important to the community, including the need to move this work along as fast as we can.

Managing the Karehana Park grate

We’ve been talking to contractors about getting a redesigned grate at the Karehana Park culvert inlet at the Airlie Rd driveway. Unfortunately that has not delivered a solution so Porirua City Council is now taking over alterations to the grate.

A winch to lift the grate at times of heavy rain is on the way and should be ready to install around the end of June or early July. A concrete base will be constructed that the winch will sit on.


We have carefully considered whether to remove the WaStop where the Airlie Road culvert flows out to sea.  It has been decided that the WaStop will not be removed due to the risk of the pipe filling with sand and the health and safety risks associated with someone having to crawl inside it to clean it out regularly.

However, a new WaStop rubber valve has been installed and will operate more efficiently than the old, worn one.

Taupo Stream Catchment

PCC and Waka Kotahi have worked together to organise drain clearing.  Blackberry and vegetation has been cleared from the drains down the western side of State Highway 1.  On the eastern side, drains have been cleared around James Street. Contractors will soon be completing drain clearing on the eastern side from the weigh station to the roundabout.

Wellington Water has met with representatives of St Theresa’s Church and School, and Jennian Homes, on long term plans to mitigate flooding and discussions will continue. A detailed project plan is currently under development.