Sunday, May 19, 2024

BOP stopbank remediation project passes halfway point

Bay of Plenty Regional Council’s Safeguarding Our Stopbanks (SOS) project is now more than halfway through its four-year schedule, with completion of the fourth and final stage on track for April 2025.

There are 400km of stopbanks in the region, which are part of a wider flood protection system that the Regional Council manages, including pump stations, floodwalls, drains and floodgates.

One of the Council’s core responsibilities is to help minimise the risk flooding poses to communities, by ensuring that its flood protection assets (such as stopbanks) are in good condition.

Project lead, Paula Chapman says the SOS project, which began in 2021, identified that structures, trees and vegetation had been established outside of residential, private property boundaries and onto public land, and were putting these flood defences at risk.

“Structures or vegetation in the stopbank can create weakness in the stopbank structure. If there is any weakness, it can create a flow path for water to get through, which could then result in the stopbank failing during a flood event,” said Ms Chapman.

“The SOS project involves working alongside landowners and specialist contractors to remove or relocate these structures and vegetations, and repairing the stopbank to a good condition by placing and compacting fill material (different soil types) and contouring the banks to a typical stopbank shape.

“Once this is done, we also grass the stopbank, as this can help protect it against erosion and hold together the soil structure underneath.”

Stages One and Two have been completed, with construction of Stage Three currently underway and due to be finished by end of this month. To date, Regional Council has repaired nearly 1.5km of stopbank and 19,000m2 of stopbank land.

Ms Chapman said project hasn’t been without its challenges, particularly as some of the private structures and landscaping on the stopbanks was largely unknown.

“Throughout the stages, we have removed nearly 30 over boundary structures or concealed objects. The concealed items have included old sumps and drainage pipes, tree stumps, debris and rubbish, which have been buried in or threaded through the stopbank,” she said.

“While we put together our best laid plans for each stage using geotechnical information, modelling and surveys, these underground ‘surprises’ are not usually revealed until the earthworks begin.

“If we didn’t find these ‘surprises’, the future consequences could have been quite serious, so while it adds more time to the job, the silver lining is that we are finding these concealed items through this process.

“When they are found, they are removed and the stopbanks repaired, ensuring that the stopbanks are in a better condition than before, and can be more effectively maintained and monitored long term.”

Ms Chapman thanked the 60-plus residents who have worked with Regional Council so far, and for their role in helping ensure the safety of the township.

“Many of the residents living in the project area have been here for years, so we appreciate this has been unsettling for them. Throughout SOS we’ve made sure our project team have been accessible and regularly communicating about what’s happening, and we will continue to work with residents as we head into the final stage.”

“We thank you for your patience, as this helps us and our contractors complete this project as efficiently as possible,” she said.

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