The report, prepared by Becca Engineering, will be tabled at this week’s council meeting.
It came after concerns about the safety of the 1.5km Outram floodbank — a sonic drill was used to collect soil samples for assessment.
The purpose of the assessment was to establish the stability of the floodbank and associated risk of failure, and to inform emergency response procedures. This in turn was intended to inform future work to improve the resilience of this portion of floodbank if needed.
But the Becca report found the floodbank was assessed as "being generally stable under expected flood and non-flood conditions".
"Under more frequent and less extreme earthquake loadings the floodbank is also likely to be stable and is unlikely to undergo liquefaction."
Seepage through the entire thickness of the floodbank was also unlikely due to the presence of silts near the surface, the report said.
"Due to the stability risks associated with normal, flood and earthquake loadings being assessed as low, the assessment concluded that implementing immediate improvements to the ground or floodbank are unlikely to yield short-term benefits."
The council infrastructure lead’s report to be presented to councillors said the Outram floodbank resilience project’s remaining budget was about $5.5 million.
This could be distributed to projects more in need of funding, such as the Silver Stream capacity maintenance project, which needed an extra $1.09m, the report said.
The Silver Stream capacity maintenance project has been regarded as high priority to the community and a contract has recently been awarded for the first stage of
physical works to begin this financial year.
This project is intended to improve the current capacity of the Silver Stream due to gravel accumulation in the reaches at and downstream of Mosgiel.
The remainder of the Outram floodbank resilience project budget could be discussed in next year’s annual plan and the 2027-37 long term plan, the report said.
The project was originally scheduled to be one of the first to begin under the council’s 2024-2054 regional infrastructure plan and would have taken about five years to complete.
