Buller District Council

Questions and Answers- Westport Water Tunnel Pipeline Project

14th January, 2019

Q1: Who is the successful tenderer?
A1: Hadlee & Brunton Ltd, directional drilling and piping contractor from Timaru.

Q2: What is the project value and when will it be finished?
A2: The expected capital cost is $6.3M. Target date for the first stage (Tunnel No.1 piped, pumps off) is 30 June 2019. Overall project completion by October this year.

Q3: What will it cost me as a ratepayer and has Council investigated other funding options to help affordability?
A3: Yes Council have taken an intergenerational approach to sharing the impact to ratepayers over the life of the asset. The estimated increase is $75 p.a. per ratepayer.

Q4: Does the project have future capability to pick up the North Branch of Giles Creek?
A4: Yes. However this has been deferred >10 years due to the excellent performance of the back-up pumped system.

Q5: How much disruption will be caused to the water supply while this project is being completed?  
A5: Minimal disruption is expected.

Q6: Will we be given advanced warning of any possible shutdowns to the water supply?
A6: Yes, notifications will be circulated before any scheduled disruption to the water supply.

Q7: How many tenders were put forward for the overland pipe project?
A7: Three – two were conforming overland pipes and one was the tunnel pipeline alternative from Hadlee & Brunton.

Q8: How much has council spent on consultants getting to this decision?
A8: Less than $200k has been spent on design consultants to date (or 3% of the project capital value).

Q9: Will local contractors be involved in the project? Will there be local employment opportunities?
A9: Yes. The estimated opportunity is $1M worth of civil, mechanical, electrical and piping works for local contractors.

Q10: How is Council going to manage the project to ensure there is no cost blow out?
A10: The contract basis has been set up as lump sum, design and build to manage risk. Council will apply project management best practices to ensure successful on-time and on-budget delivery.

Q11: The pumped supply has been working well for the last 12 months with the leaks fixed, why not continue to use that and save spending money? What will happen to the pump station once the project is completed?
A11: The best long-term (100 year) solution is the gravity flow pipeline. The pumped system has proven to be an excellent back-up and will be maintained in that capacity should it ever be required.

Q12: Has anything been learned from all the reports and the previous tender process?
A12: Yes. By examining and comparing each of the options at an appropriate level of detail, the best long-term solution for Westport has been found.

Q13: What about the state of the trunk main to town? Is an upgrade of this line not needed now?
A13: The trunk main is not part of this project, but it is another key component of the water supply system. Currently under an active leak-fix program, trunk main replacement would be another multi-million dollar investment for Council to consider in future years.

Q14: Why does this project need resource consent when we already used the tunnels?
A14: Due to the nature of the site preparation and directional drilling work, resource consents have been obtained to ensure full compliance with planning requirements

Q15: Has Council considered an alternative supply instead of Giles Creek?
A15: Yes. Other water supplies including the Buller River and a deep bore aquifer were previously considered by Council. However the decision to stay with Giles Creek was made because of the outstanding water quality, the existing treatment plant location and the benefits of gravity flow supply.

Q16: Why doesn’t Council just fix the collapsed Tunnel No.1?
A16: Just fixing the tunnel isn’t the best long-term, value for money solution when considering residual risk. Repair options including stabilisation could still cost $3M with no guarantee against further roof collapse and blockage. A steel pipe through the tunnel improves the resilience and reliability of Westport’s water supply.

Q17: Why is steel pipe being used for Tunnel No.1 instead of PE pipe and won’t the steel corrode?
A17: Grade 350 12mm thick steel pipe has been selected for Tunnel No.1 due to its superior structural strength and crush resistance. This significantly reduces the risk of pipe rupture should unstable sections of tunnel roof continue to fall. Steel pipes are commonly used for water lines with no issues of contamination or degradation. In terms of durability, steel outperforms PE which is critical given the collapse zone sits 180m below natural ground. Corrosion rates will be monitored as part of routine inspections. If the pipe wall thickness reduced, it could then be lined with 710mm PE pipe to extend lifespan. However, this may not be required for another 50 years or more.

Q18: What happens to the pipes if the tunnels collapse and how would a pipe rupture be fixed?
A18: The steel pipe for Tunnel No.1 will withstand substantial impact without rupturing. Most roof collapse is expected to occur during installation, after which it should stabilise. Should a major earthquake cause catastrophically damage, the fix would involve directional drilling again. The other tunnels are less prone to collapse and far more accessible, hence the selection of PE pipe.

Q19: What makes piping the tunnels a better solution than an overland pipe?
A19: The clear advantages of the tunnel pipeline alternative are:

  • Improved safety – no tunnel entry required during the pipe installation and safer work sites
  • Shorter timeframe – pumps off within in 6 months
  • Less impact to environment and adjacent landowners
  • Lower ongoing maintenance costs

Q20: Why didn’t we do this two years ago when the tunnel collapsed?
A20: Put simply, the risk was too high. Uncertainties around safety, technology and cost would have exposed Council and ratepayers to unacceptable consequences. Due diligence processes discounted other options such as tunnel repair, pipe jacking and overland pipe. Directional drilling only became credible once an expert practitioner could prove how risks would be appropriately managed. Hadlee & Brunton explained the following reasons why they could now tender:

  • The extensive planning assessment detail provided by Council
  • Securing a suitable pipe thruster already in NZ, significantly reducing lead time and costs
  • Advancements in drill tooling, patented jointing methodologies and camera inspection technology
  • Additional investment to complete risk mitigation design and resource consent investigations

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