Public Health Warning Urged After Flood Leaves “Putrid” Contaminants

There are calls for a public health warning to be issued following the most recent Hawkesbury floods following confirmation of a “putrid” level of contaminants found in the flood water, with the Council run sewerage treatment plant at McGrath’s Hill also flooded.

Leading water Scientist, Associate Professor Ian Wright from Western Sydney University said the contaminants found in the flood waters in this flood are some of highest and most concerning they had ever seen.

Wright has been surveying local  rivers, taking water samples on April 5 and April 6 as the flood waters were rising. He told ABC Radio that he and his students tested the water at the University on Monday and Tuesday and found it was “absolutely loaded with pollutants and it just confirmed how dangerous that can be.”

He said the waters were full of sediment but more seriously e-coli, an indicator or fecal contamination. “I’ve worked with Sue Cusbert, a lab technician who has been doing this for decades and she said she has never seen results off the scale like they were, Wright said.”

He said the contamination was coming from any warm blooded animal waste, “anything that was in the paddock, the footpath or the park that was flushed into the river” during the heavy rains as well as from the regions sewers. 

“So many of our sewerage assets are located below down near the water line, most of that is under our feet, the sewers that gravitate away from the house. A lot of rural houses have their own on site system and so much of that got flooded. 

Near Windsor, McGraths Hill Hawkesbury City Council has a sewerage treatment plant that includes ponds. “That was all flooded by the South Creek flood which banked up from the Hawkesbury. Basically a lot of that flood water was diluted sewerage,” he said.

But an HCC spokesperson downplayed the problem. 

“The floods in April 2024 had a direct impact on the constructed wetlands which are part of the treatment process at the McGraths Hill Sewage Treatment Plant,” an HCC spokesperson said,  “The treated waters in these constructed wetlands have, by that stage, already undergone a secondary level treatment and would represent no greater source of water pollution than runoff from a typical urban catchment.”

Wright  said the chemical levels found in the water were “astounding.” The nitrogen levels they found were 10 times the safe levels and phosphorus levels were “sky high” approaching 100 times the safe level for waterways. He described these as a “ticking time bomb” potentially creating algae blooms and posing a threat to the fish population.

“The management of the Hawkesbury River, including water extraction, is the responsibility of the NSW Government. Council maintains that people should not enter or come into contact with floodwaters, and should take adequate measures to protect themselves during clean-up activities, including NSW Health’s advice on staying healthy during and after floods available,” the HCC spokesperson said.