Otago Regional Council

2024-10075 - Balclutha Relief Wells Remediation

The Otago Regional Council (ORC) currently maintains a number of flood banks and associated structures across the Otago region. This section of work is located in Balclutha on the true right of the Clutha River/Mata-Au flood bank. During the February 2020 flood event, two relief wells showed signs that there may have been failure of these wells. One well indicated subsidence and the other significant discharge of sediment. Annual well inspections determined that approximately 1 m of sediment had built up in many if the wells as a result of the 2020 Flood.
This opportunity involves the following work:
• Replace wells numbered 3, 7 and 9 each with two new adjacent wells in accordance with the repair design included in the T+T 2020 report.
• Repair or replace wellheads at wells 5 and 17b where PVC wellheads are broken.
• Undertake grouting of the base of all existing wells to reduce the potential for sediment inwash. This will likely prolong the life of the wells and reduce the potential for the wells to become blocked with sediment via the base in future floods.
The work will require careful planning and coordination to minimise adverse effects on the environment and maintain flood protection measures over the duration of the works.

Department/Business Unit: Engineering