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Published 10/11/2020

Hutt residents asked for views on improving the wastewater network to reduce overflows

Media Release

Wellington Water is asking for public input about the impact of any wastewater overflows in their local area.

Although Wellington Water’s data shows that large overflows are infrequent across most of the network, any overflow that results in human waste getting into our waterways is objectionable.

Overflows contain bacteria that may make people sick if they come into contact with contaminated water. This is why people are advised not to swim for 48 hours after heavy rain.

Wellington Water Chief Advisor Wastewater Steve Hutchison says there is an ongoing programme of upgrading and repairing the aging wastewater network.

“For example in recent years we’ve managed to significantly reduce overflows into Waiwhetū stream, from up to 30 a year to fewer than two a year. We are continuing to work with property owners in this area to fix drains on private property.”

“We know overflows following heavy rain are more frequent around Black Creek in Wainuiomata and near the Wainuiomata Coast Road storage tank. We have an ongoing pipe renewal programme in Wainuiomata and we are actively monitoring flows through the network and water quality in Black Creek and Wainuiomata River.”

“Our data also shows that wet weather overflows happen from the Silverstream storage tank to Te Awa Kairangi / Hutt River about five times each year during periods of sustained wet weather. Ongoing work to upgrade the network and reduce inflow and infiltration should play a part in reducing the frequency of these overflows over time.”

“We’re now asking for people’s views about the impact of overflows in their local area, and any further information about where and when they happen, so we can finalise a picture across the whole network.  This will help us set future investment priorities.”

Community feedback will be reflected in an application for a network-wide resource consent for wastewater overflows, replacing a number of current discharge-by-discharge consents.  

Lower Hutt and Upper Hutt residents can see a map of the network and comment on the impact on their local streams and rivers, on Wellington Water’s online engagement page.



Any water that goes down the toilet, sinks or household drains is wastewater and is carried along a network of over 900 km of pipes and two storage tanks to the Seaview Wastewater Treatment plant. There, it’s cleaned and disinfected and treated water is discharged out to the Cook Strait at an outfall past Pencarrow.

The network and the treatment plant are managed by Wellington Water on behalf of the Hutt City Council and Upper Hutt City Council. 

The network is designed to be able to carry four to five times more water than the average daily flow, so that it can cope with extra water, for example when it rains. Sometimes when it rains very heavily, there is more water than the pipe network can carry and untreated wastewater will overflow from specific points into streams or rivers. If pipes get blocked, overflows can happen anywhere across the network in any weather, but these are usually only small amounts, and fixed quickly.

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