Buller District Council

Westport & Carters Beach Water Supply – Repair of No.1 Tunnel

11th May, 2017

The reservoirs for the Westport & Carters Beach network are normally supplied through a gravity-flow tunnel system upstream of the treatment plant.  After the partial collapse of No.1 Tunnel in 2014, Council commissioned an options study to identify the best solutions.

Several options were proposed, including tunnel repair (stabilisation), microtunneling (pipe-jacking) and directional drilling.   The tunnel repair option was selected on the basis of affordability, whilst acknowledging this was a medium-term solution that would still leave Council with a moderate level of risk.

Further collapse and obstruction within the No.1 Tunnel occurred earlier this year, resulting in no water flow passing through. Water is therefore being supplied to the reservoirs from the alternative pumped system which must operate continuously to meet demand.

In addition, recent changes to Health & Safety and legislative requirements means that tunnel repairs must satisfy mining and quarrying regulations, causing an escalation in risk control measures and costs when compared to the original options study assessment.

Therefore, Council have revisited the decision of tunnel repairs. At an extraordinary public excluded meeting held yesterday, Council resolved to eliminate this option from consideration, on the basis that a longer term solution with lower risk may be more economically comparable.

With tunnel repairs now eliminated, the focus of the current feasibility study will shift to selecting a new go-forward option from those remaining. A recommendation based on the feasibility study will still be presented to Council in June as originally scheduled. If the recommendation is approved, implementation of the new option will proceed.


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