Council votes for hinged barrier across weir pool
19 June 2020
Project Reference Group recommended barrier best way to keep high tides out
Council yesterday resolved to progress with the concept design of a hinged barrier across Bray Park Weir to protect the Tweed District Water Supply from the risk of tidal inundation.
Council adopted this solution identified by a community Project Reference Group, which had been working on the difficult problem of saltwater contamination of the weir pool since March 2018.
The Tweed District Water Supply is at risk of saltwater contamination due to an increased frequency and intensity of high tides overtopping the weir wall.
The risk is heightened during times of low flow in the Tweed River which are insufficient to hold back an upcoming tide.
The risk is becoming more intense due to an increasing frequency of sea level anomalies, where actual tide heights exceed predicted tide heights.
In August 2017, the first of these sea level anomaly events resulted in a lot of saltwater getting into the weir pool, stopping the production of drinking water supplies for two days. The weir pool had to be dredged of the saltwater, at a cost of more than $400,000.
Since then, Council has prevented 26 overtoppings by manually placing heavy concrete blocks on the weir wall.
However, in the early hours of Monday 25 May this year, about 15 million litres of saltwater entered the weir pool on a higher-than-predicted tide. By the time Council staff realised the tide was significantly higher than predicted, it was too late and too dangerous for staff to deploy the concrete blocks. That saltwater remains at the bottom of a deep water hole within the weir pool and has not affected the production of the Tweed’s drinking water.
“We have been managing the risk of tidal inundation of the weir pool for many years, first by placing sandbags across the weir wall and now by placing large concrete blocks on the wall, so we welcome Council’s decision to progress with the concept design of a hinged barrier,” Manager Water and Wastewater Business and Assets Anthony Burnham said.
Once a concept design is developed, cost estimates will be updated and this will be provided to Council to gain approval to proceed.
“We look forward to progressing this project, as not only will it protect the Tweed District Water Supply from saltwater contamination but also our workers from the risks of manually placing large and heavy concrete blocks in often slippery conditions and against strong downstream flows over the weir wall.”
For more information on this project, visit https://www.yoursaytweed.com.au/BrayParkWeir
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Caption: The Tweed District Water Supply is at risk of saltwater contamination due to an increased frequency and intensity of high tides overtopping the weir wall. The Bray Park Weir supplies raw water for the Tweed.