A two-week Otago Regional Council drilling and material testing programme is scheduled to begin next week on the 1.5-kilometre Outram floodbank.

ORC’s Manager Engineering Michelle Mifflin says planning for the investigation started in mid-2023 as part of ORC’s ongoing flood bank asset management and investigation programme, with resource consent having only recently been gained.

She says the floodbank is around 120 years old and the information gained from the test drilling and core samples will help inform the future design of planned improvements works.

The Outram floodbank is one of the ORC’s oldest assets, having been constructed in the late-1800s using horse and cart, with likely a variety of construction materials used during that period.

Ms Mifflin says while the investigation is “business as usual” for ORC’s Engineering team, she is “curious” what the drill programme will reveal of the underground geology and hydrology, the flood bank’s material make-up and history.

The works are weather dependant, but scheduled to start on Monday, 4 March for about two weeks.

Outram residents will see a mobile drill rig drilling 100mm diameter holes, and undertaking cone penetration tests along the floodbank, with the drill core samples and test results to be analysed over several months.

“This work will help inform us on the floodbank integrity and confirm maintenance and replacement programmes in the future, which could span decades ahead,” she says.

The drilling programme is estimated to cost about $120,000 under work provisions in the ORC’s Long-Term Plan and will also include costs around the installation of permanent water monitoring equipment in three of the holes.

More than 200 kilometres of flood banks

Otago is the country’s second largest local government region.

ORC’s Engineering team has responsibility for flood protection and land drainage which provides flood protection to approximately 43,000ha of rural and urban land in Otago – in total, seven flood protection and/or drainage schemes.

Engineering manages infrastructural assets including 218 kilometres of flood banks, 14 pumping stations, 55 bridges, culverts and a variety of other assets.

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