Ravensdown has said it was the source of the stench as it worked to clear stormwater ponds while trying to work within the wildly changing wind forecasts.
One Ravensbourne resident said the odour was "your classic rotten egg, sulfuric smell".
"It’s very strong, and not let out all the time ... Whatever they’re doing out at Ravensdown, it’s letting out some toxic, foul-smelling sulfuric gases."
He said when the smell came, it was as if someone dropped a "bomb".
"You can almost gag when you breathe it in — it affects my throat, it affects my nose."
He said this was just the latest in a long list of inconveniences the Ravensdown factory had caused residents.
"Ravensbourne residents have been cutting up this for 90 years."
Windows clouded over due to emissions from the plant in the early 2000s — "the plant’s got a history with us", he said.
West Harbour Community Board member Jarrod Hodson said while he had not noticed the smell as he was usually out of the house during the day, he had followed up after hearing complaints from many in the community.
He said he was told the cause of the smell was the drainage of stormwater ponds by Ravensdown.
"They’ve been doing it over the last few weeks, but because the weather’s been so erratic, it’s affected it and made the smell go up through Ravensbourne."
Mr Hodson said Ravensdown was already 85% through the work, and once completed the stench should not come back.
Ravensdown chief environment and sustainability officer Anna Wilkes said clearing the stormwater ponds meant there was sediment exposure during the cleaning process.
"[This] means there is a localised odour — while the scent can be unpleasant, it is not a health issue."
She said the team was working "really hard" to minimise the odour and any impact, and they apologised for the inconvenience and disruption.
"We are monitoring wind conditions and are only scheduling work on days when the weather forecast is for wind that is strong enough to blow odours offshore."
However, despite best efforts, the wind speed and direction had been different from what had been forecast.
"At this stage, we expect the work to be complete within the next fortnight — weather permitting. [We] thank everyone for their understanding and patience during this time."
She said Ravensdown was in direct communication with the Otago Regional Council and was keeping it informed.
Ravensdown closed the Ravensbourne site mid-January, and decommissioning was completed a few months ago.
The site is now operating as a port store and distribution centre.
