Buller District Council

Media Release-Westport Water Tender – Underground Pipe to Proceed

20th December, 2018

Council confirms it will now proceed with the Westport Water project. A Letter of Intent has been awarded to Hadlee & Brunton Ltd who proposed an underground pipe alternative in lieu of the overland pipe outlined in the tender.

Key to their alternative is the directional drilling of the collapsed Tunnel No.1 and lining it with steel pipe using the latest in technology and equipment. Tunnel’s No.2 and No.3 will then be piped with polyethylene (PE) similar to Tunnel No.4 which was done eight years ago.

The overall scope also includes PE pipe from the existing Giles Creek south branch intake, connections between the tunnels and through to the reservoir ponds forming one continuous, end-to-end gravity flow pipeline.

Through an intensive ‘weighted-attribute’ tender evaluation and due diligence process, Hadlee & Brunton’s proposal demonstrated the following clear advantages:

  • Better safety – no tunnel entry required during the pipe installation
  • Shorter timeframe – water flow in 6 months for first stage
  • Less impact to environment and adjacent landowners
  • Lower ongoing maintenance costs, most direct route (2.5km instead of 3.8km)

Resource consents have now been obtained, confirming the project is ready for implementation in two stages. Stage 1 costing $5.4M for the steel pipe through Tunnel No.1 will take 6 months to complete, at which time the current pumped system will be turned off. Stage 2 to install PE pipe for the remaining length will cost $0.9M and a further 3 months. The opportunity for significant local content exists for electrical, mechanical, earthworks and pipe installation services.

Despite the budget increase from the original $3M, Councillors voted unanimous to approve the underground pipe alternative. The main concerns were impact to ratepayers, safety and long-term reliability. With depreciation and loan interest periods spread over the asset lifetime, the rate increase from the LTP is estimated at $75 per year.

Mike Duff says “The entire planning phase has been about risk management – safety, scope, cost, time, and quality. All the aspects critical for a project of this significance. We have taken a design-build, lump sum approach, with a technically sound solution and a highly respected practitioner to deliver”.

“By considering all alternatives, we have found the best outcome. Eliminating tunnel repairs was the right idea from a safety aspect, which lead to the overland pipe tender. But that didn’t rule out tunnels. The door was left open for an innovative approach, and in came Hadlee & Brunton”.

The project team has operated on two key principles throughout – health and safety (during construction and ongoing operation) and gravity flow from Giles Creek to the reservoir ponds. Directional drilling with Hadlee & Brunton’s construction methodology avoids any need for tunnel entry while installing the pipeline.

“As we’ve said before, the tightening regulatory environment and compliance for people working underground is getting more complex and costly. We must consider maintenance personnel and our ongoing duty of care throughout the asset lifetime – no tunnel entry for maintenance eliminates the hazard and changes the risk profile.”

Once installed, the underground pipeline will convey water on hydraulic grade, the same way as the tunnel system did for 100 years. No syphoning or high-maintenance vents and scours are
required – just good old fashioned gravity flow.

Steel pipe has been chosen on Tunnel No.1 for its structural integrity and crush resistance should further roof collapse occur over time. Although more expensive than the base PE option, 12mm thick steel significantly reduces the likelihood of future pipe blockage or failure.

“This is the game-changer from a residual risk perspective and one that earlier tunnel repair proposals lacked. The steel and PE pipe solution delivers the ‘Fit for Future’ imperative underpinning the entire project. We think another 100 years of trouble free operation is a reasonable expectation for Westport ratepayers.”

Council intends to hold a public meeting early in the New Year to provide the community with more project details. Initially planned for this week, it was considered better to defer until after the Christmas break when more ratepayers could attend. The meeting is scheduled for 6pm Tuesday 15 January 2019 at the NBS theatre.


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