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Unlocking solutions: Council contributes to Pambula and Merimbula lakes study

Bega Valley Shire Council, UNSW Water Research Laboratory (WRL) and the NSW Food Authority are collaborating on research into the impacts of sewer spills on local aquaculture.

Pambula Lake and Merimbula Top Lake will undergo a safe regime of dye tracing in early July.
Pambula Lake and Merimbula Top Lake will undergo a safe regime of dye tracing in early July.

30 June 2023

Bega Valley Shire Council, UNSW Water Research Laboratory (WRL) and the NSW Food Authority are collaborating on research into the impacts of sewer spills on local aquaculture.

Council’s Water and Sewerage Services Manager, Steve Marshall said the study aims to reduce oyster farm closures by understanding spill effects better.

"Council always works closely with oyster farmers to minimise the frequency and impact of sewer spills on their product and livelihoods," Mr Marshall said.

“While sewer spills are rare, they do have the capacity to significantly impact a thriving and award-winning local industry.

"By studying sewer spills, WRL aims to develop a decision support matrix that guides authorities in handling aquaculture industry closures following overflow events.

“The outcome will be to bookend a response mechanism, with Council working with the community to reduce the likelihood of sewer spills at one end and the findings of this study delivering a better procedure for authorities at the other.” 

Mr Marshall said sewer spills are mostly caused by blockages and overloading of the sewerage network.

“Blockages from tree roots and items like nappies, wet wipes and oils that have no place in a sewer, can cause a spill that sometimes reaches our waterways.

Spills can also happen due to wet weather, where non-compliant stormwater connections and water ingress through manhole lids and pipework can overwhelm the system,” Mr Marshall said.

“Measures we use to reduce the frequency and impact of spills include sewer camera investigations, mains high-pressure jetting, pump station cleaning, smoke testing and renewals and upgrades to the network.

“These measures are focused on areas categorised as high risk, such as around waterways.

“This academic study on spill response management will complement our efforts and help to improve our existing Pollution Incident Response Management Procedure for spills.”

The study will commence with WRL conducting dye testing at Pambula Lake and Merimbula Top Lake.

“Field dye tracer experiments use a red dye (Rhodamine WT) to track effluent dispersion in estuaries,” Mr Marshall said.

“The dye is harmless to aquatic eco-systems and non-staining and it has been used at recent successful experiments in NSW.

“The research project, funded by the Regional NSW Sector Recovery and Resilience Grants, demonstrates a collective commitment to protecting local aquaculture and ensuring its long-term sustainability.”

Dye tracing will be conducted at Pambula Lake and Merimbula Top Lake from 4 to 6 July. The red dye will be visible for a few hours before dissipating.

For more information, please call the UNSW Water Research Laboratory on (02) 8071 9800.

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