It comes after residents raised ongoing concerns about discharges from the wasterwater treatment plant which overflow into Duchess Creek and on to Rainbow Beach.

In a report to the May council meeting, director of infrastructure Dan Bylsma said council acknowledges the sewer system has some shortcomings and are working to rectify surcharge issues across the local government area, with priority given to catchments that experience surcharging inside properties.

"It should be noted, thought that in a heavy rain event, there is little that can be done, even with the best sewer system, to prevent an overload of the network and subsequent surcharging," Mr Bylsma said.

Overflows are not uncommon in coastal catchment areas and council is licensed by the EPA to overflow via Duchess Creek to Rainbow Beach.

Residents raised concerns about the health hazards for beach users caused by discharges from the wastewater treatment plant and associated sewage infrastructure.

"Overflows are not uncommon in coastal catchment areas as sewerage systems are not designed to transport stormwater in heavy or sustained rain events. This is why the EPA provide conditions in sewerage system licences for the overflow of untreated or partially treated sewage to a specified location where it is heavily diluted," Mr Bylsma explained.

"In sustained and high intensity rainfall and with large amounts of stormwater, the storage ponds at the wastewater treatment plant fill faster than the plant can treat and once they reach full capacity, the excess discharges in line with the designated overflow and council's EPA licence."

Overflows to public recreation waterways are not uncommon across the state.

Advice from NSW Health following a heavy rain or storm event is to avoid using any public recreation waterway for a minimum of 24 hours and up to three days.

"Surcharges of the sewer system also occur as a result of stormwater inflow and infiltration and there is often little we can do, even with the best system in place, to prevent an overload of the network and subsequent surcharging in high intensity rain events," Mr Bylsma said.

Council is currently developing a sewer event 'hot spot' map. This will be overlayed with the existing stormwater 'hot spot' map to identify recurring issues and prioritise remediation works throughout the local government area.

Council is also set to commence a sewer mains relining program in the 2021/22 financial year. The initial relining program will be directed towards catchments with a history of multiple breaks.

Within council's 10 year works program, it will also undertake an holistic risk assessment of the sewer network to establish an overall plan for prioritisation and remediation works and proactive maintenance.

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