A stinky smell lingering in suburbs around Newcastle and in parts of the Lower Hunter has been identified as a naturally occurring gas emanating from a “blackwater event” in low-lying wetlands, the NSW Environmental Protection Authority says.
From Merewether to Maitland, residents woke on Sunday and Monday to a strange smell which some described on social media as like a “chemical”, “sewerage” or “septic” odour.
The EPA first responded to residents’ concerns on Sunday via Twitter, saying the odour was related to a “naturally occurring gas possibly associated with stagnant water”.
READ MORE: Gas-like odour lingers in Newcastle suburbs
But an EPA statement released on Monday confirmed the smell was the result of a blackwater event following recent heavy rainfalls in the Hunter.
“The EPA is aware of the strong sulphur-like odour across parts of the Newcastle region,” the statement read.
“The odour is associated with a naturally occurring gas that emanates from a blackwater event.
“Recent heavy rainfalls have created large tracts of stagnant water in low-lying wetland areas along with deposits of organic matter.
“Warmer than average temperatures and high tidal ranges around the recent full moon have also led to the organic matter decaying more quickly and generating a strong smell.”
People reported the smell from coastal areas, inner and outer-Newcastle suburbs, and in the Lower Hunter around Maitland.
EPA is aware of the gas-like odours across parts of the Newcastle region today. FRNSW officers attended & found no gas emissions. The odour is likely to be naturally occurring gas possibly associated with stagnant water after recent heavy rainfall & will disperse with wind.— NSW EPA (@NSW_EPA) April 1, 2018
Maryville resident Edel Sarmiento Baggs told the Herald her friends and family had picked up on the odour in outlying suburbs.
“I have been awoken by such a strong chemical or septic-tank kind of smell for the past two days,” she said.
“My friends at Lambton said the same thing. Even relatives from Shortland and Thornton.”
Nicole Francis, of North Lambton, said the odour was so intense she felt sick.
“The smell was so bad this morning that it made me really nauseated,” she said. “I had to check that the sewage lines outside weren't broken. It was really bad.”
According to the Commonwealth Environmental Water Office, of the Department of the Environment and Energy, Blackwater forms “when flooding occurs after prolonged dry periods when temperatures are warm and there has been an extensive build-up of organic material, such as leaf litter”.
When the organic material is washed into the water, increased bacterial activity can result in deoxygenation of the water.
The process can lead to the death of aquatic organisms, with native fish and crustaceans especially vulnerable to oxygen deprivation.
A blackwater event occurred in the region during January, 2016 and led to a rotten egg-like odour hanging around Hexham, Beresfield and Raymond Terrace. It was reported at the time the event caused fish deaths in the Hunter River.
The EPA did not say how long it will take for the current smell to clear.
“The odour will disperse with wind, and a change in weather conditions,” their statement said.