Sewer Overflows – The impact of heavy rainfall

23 March, 2021

With the recent rainfall Council has experienced a number of wet weather overflows of sewerage system.

One cause of wet weather overflows is rainfall infiltrating through the ground into leaky sewers. Excess water can also inflow through downpipes illegally connected to sewers and broken or badly connected property sewer/drains. This infiltration/inflow can significantly increase flows in sewers during wet weather far beyond the design storm allowance made for the sewers. Exceeding the capacity of the sewers causes overflows at overflow structure points, maintenance holes and at the sewage treatment plant. The extent of this problem varies within and between systems, depending on factors such as rain intensity soil conditions and infrastructure conditions. The operation of every sewerage system in Australia is affected to some extent by infiltration/inflow, and/or illegal connections of stormwater. The impact of infiltration/inflow is a significant if the sewers or property sewers/drains are in poor condition.

This is not a new problem and Council in the last 10 years has invested significant funds toward reducing inflow and infiltration into the sewerage system and in the last 3 years has targeted illegal connections of stormwater to the sewerage system. Whilst there has been a significant reduction over this time there is still a considerable amount of work required to reduce the potential for wet weather overflows.

Whilst in many events there is little Council can do, residents should still report surcharging sewers on (02)6354 9999 or email [email protected] as the overflow may not be as direct result of the wet weather.