Tauherenikau River Water Pipe Repair

The pipeline that supplies drinking water to Featherston is leaking on the section that crosses the Tauherenikau river.  Repair work has commenced on an interim fix while a permanent solution is awaiting approval, and Council will post regular reports of progress from Wellington Water Ltd on this page.

Background

Featherston’s water network is supplied by a transmission pipe from the Waiohine Water Treatment Plant. Where the pipeline crosses the Tauherenikau river, the section of pipe that is exposed is approximately 23m long. Of the exposed section, around 15m of pipe is concrete encased and the remaining 8m is made up of steel pipe. A break in a coupler on the exposed section was identified on 3 December 2021.

The leak only became visible when the river level was low. The area of the pipe around the leak suggests this may have been leaking undetected for some time and not visible due to high river levels.

The Featherston network serves a population of approximately 2,500 people with 36 kilometres of watermain. The network serves residential, commercial, industrial, and community users.

The three main water sources for Featherston are:

  • Waiohine River – current
  • Taits Creek Intake Weir – emergency supply only
  • Bore Bush Gully Catchment – not in commission

An automated pressure alarm has been installed on the pipe downstream of the leak to monitor the pressure in the pipe. If the pressure drops too low this will trigger the alarm to Wellington Water’s on-call staff in the area as it could indicate that the leak has worsened or failed completely.

A contingency plan for this scenario has been refined and a repair plan has been created. A long-term upgrade solution has been presented to South Wairarapa District Council.

The fix identified is in two phases: the first to stabilise the existing pipe to ensure sustainable water supply in the short term, with a second to replace the pipe with a fully sustainable system that will last many, many years.

Project Milestones

Site establishment – 28 March 2022
Boar Bush reservoir back in service – 31 March 2022
Temporary works in river – 8 April 2022
Repair leaking coupling – 11 April 2022
Rip Rap placement – 18 April 2022
Reinstatement and Disestablishment – 28 April 2022

Current state

As of 30 March 2022, the Wellington Water team are on site and ready to begin a repair work on the water pipe that crosses the Tauherenikau river.

Contingency plans are in place to minimise the risk that the water supply to Featherston is interrupted during this repair. These plans include making sure the local water supply reservoir at Boar Bush is back into service following critical maintenance works that have been undertaken, amongst other measures.

Progress Report/s

28 March 2022

Work completed this week

  • Follow up with GWRC regarding resource consent.
  • Site establishment
  • Boar Bush reservoir Bacteriological testing to bring it back in service
  • Pipeline shutdown contingency planning
  • Weather permitting and subject to resource consent, construct coffer dam in Tauherenikau river

Work to be completed next week

  • Deliver Class C rip rap to site
  • Backfill scour hole underneath exposed steel pipeline to install temporary pipe supports
  • Expose leaking coupling for repair
  • Undertake repair to coupling

Issues Challenges

  • Boar Bush reservoir is currently out of service following the February contamination event.
  • Increase in river levels and delays in resource consent has impacted progress with temporary works on site.

1 April 2022

Work completed this week

  • Resource consent obtained for river works
  • Site establishment – Excavator and site container delivered to site.
  • Boar Bush reservoir back in service

Work to be completed next week

  • Pipeline shutdown contingency planning
  • Weather permitting, construct coffer dam in Tauherenikau River.
  • Backfill scour hole underneath exposed steel pipeline to install temporary pipe supports
  • Expose leaking coupling for repair.

Issues Challenges

  • Wet weather increasing river water levels and presenting unsafe working conditions (flood). Wellington Water and Fulton Hogan monitoring river levels daily to find most suitable conditions to undertake works.
  • Increased river baseflows due to change in season.

Timeline

Day: 191 of 31
Start: 28 Mar, 2022
End: 28 Apr, 2022

Location

Waiohine Water Treatment Plant pipeline crossing of the Tauherenikau river

Contractors

Wellington Water

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