Both Fire and Emergency New Zealand crews in Mataura and a hazardous materials command post from Invercargill were called out just after noon yesterday, when a sprinkler alarm was reported in the disused paper mill.
The building is now used to store ouvea premix, a by-product of production at New Zealand Aluminium Smelters’ (NZAS) Tiwai Point facility.
If the dross mixes with water, it can create a toxic ammonia gas cloud.
This is the second scare involving the dross in six months, following the Mataura River flooding in February.
The dross sits atop wooden pallets, which were just high enough to keep water from reaching the substance, Mataura Community Board member Steve Dixon said.
"It’s lucky that the stuff was off the floor because this was not the first time water has come along, and it could happen again ... We have to keep the stuff moving and get it out."
Mr Hicks said the dross should never have been moved to Mataura, and yesterday’s incident showed it needed to be moved away as fast as possible.
"It’s disappointing that this has happened ... I wouldn’t say a bullet dodged, but the sooner we get that substance out of the building, the happier everyone is going to feel."Emergency services had done a good job to respond so quickly to the potential emergency but they and the township should not have been in that situation, he said.
"We have a contract. I don’t know the exact tonnage that has come out of there but I believe it is up to 1500 tonnes, so it is moving ... but certainly getting it uplifted and shifted to another site would be fantastic.
"That has been challenging but that’s not to say we are not pursuing all options."
In March 2018, local authorities, the Government and the smelter agreed to a $4million plan to move the waste from Mataura and other sites around Southland over six years.
The Environmental Defence Society filed Environment Court proceedings against NZAS earlier this month that claim the firm has responsibility for removal of the waste.
A Fenz spokeswoman said a sprinkler outside the building appeared to have broken due to frost, and crews found "four inches" (10cm) of water inside on the floor of the building.
However, they did not find any toxic gas, and the scene was turned over to the building owner, she said.
"There was no need for decontamination ... Initially they said it was mixing with the ouvea but they did a gas reading and there was no sign of contamination."
Fenz was well aware of the potential dangers at the site, hence the high number of people called out, she said.
State Highway 93 between Clinton and Mataura, as well as several local roads, were closed as Fenz investigated the scene.
