Tides overtop weir as Council continues discussions on solution

27 May 2020

Incident shows business-as-usual doesn’t cut it

Higher than predicted tides overtopped Bray Park Weir in the early hours of Monday morning dumping about 15 million litres of salt water into the weir pool for the Tweed District water supply.

The salty water, which is heavier than fresh water, is contained in a deep depression of the weir pool and is not affecting the quality of the water supply, as Council is drawing its raw water from the top levels of the weir pool for treatment at Bray Park Water Treatment Plant.

The overtopping occurred as a result of the actual tide being 320mm higher than the predicted tide. This was caused by what is called a sea level anomaly.

The current run of sea level anomalies is predicted to peak today and begin to weaken later this week. Then, more dangerously, monthly high tides are predicted for the week from Wednesday 3 June to Tuesday 9 June.

“Monday’s overtopping event highlights the significant risk in managing the weir using current business-as-usual approaches and modelling forecasts,” Manager Water and Wastewater Business and Assets Anthony Burnham said.

“By late Sunday when we knew the tides would be much higher than predicted, it was too late and too dangerous to ask our workers to place the blocks on the weir.”

Council has been working with a community-based Project Reference Group to identify a solution to the problem since a major overtopping event shut down the production of water for two days in August 2017.

Last Thursday, Council deferred discussions on the PRG’s recommended solution. It will now continue discussions at a workshop next month.

“The deferral of a decision and the need for councillors to further discuss and understand this issue highlights how complex it is,” Mr Burnham said.

“We look forward to next month’s workshop as Monday’s incident and the ongoing risk for the next few weeks again reinforces that we need to find a better way to mitigate this tidal inundation risk and manage our water supply for the future.”

For more information and background about the Bray Park Weir project visit https://www.yoursaytweed.com.au/BrayParkWeir

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Caption: Council staff manoeuvre a concrete block into place to stop salt water infiltration during a previous event – a difficult task.