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Sewer fix requires temporary dam for New Plymouth stream

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PUBLISHED: 13 MAR 2025
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A tricky sewage pipe replacement will see NPDC temporarily diverting an inner-city stream to get the job done.

A cofferdam – a dam placed mid-stream to create a dry work area – will be built with sandbags in the Mangaotuku Stream next to Devon Intermediate School’s sportsfield for up to three days while a trench is dug and a pipe laid beneath the stream bed.

NPDC Project delivery Manager Sean Cressy says the stream’s flow will be pumped to the other side of the cofferdam during the work.

“It’s actually a small job in terms of the length of pipe we’re replacing – about forty metres in total and only three metres across the stream.  But it’s technically challenging because we need to dig beneath the stream bed as the soil is too rocky for drilling a pipe horizontally,” he says.

“We’re doing the work during the driest part of the year so that the stream’s flow is as low as possible, and we have plans in place for managing fish in the area and reinstating the stream bank.

“The condition of the current sewage pipe means it must be replaced before it fails and causes a health and safety issue for the environment.”

The work started this week and will be finished by mid-April.

Also starting at the end of March is a sewer pipe replacement on Ocean View Parade, near the New Plymouth Yacht Club.

The current pipe is in poor condition and currently needs to be flushed up to three times a year for it to continue operating well. Installation of the 200m replacement pipe will finish in mid-June and traffic management will be in place during the project.

These projects are part of NPDC’s $248m investment to fix the district’s plumbing in the 10 years to 2031.

Fast facts:

  • NPDC collects and treats sewage from the urban areas of New Plymouth, Bell Block, Waitara, Inglewood and Ōākura and returns clean water to the environment.
  • On average, NPDC handles 25 million litres of wastewater each day, looking after more than 37,200 properties in the district.
  • Our sewer network includes 631km of pipes and 34 pump stations.

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Page last updated: 11:20am Thu 13 March 2025

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