Hypersaline water leaking into Adelaide mangroves as ‘horrible history repeats’

Hypersaline water is again leaking into mangroves from faulty ponds in Adelaide’s north, prompting calls for urgent action to avoid a repeat of last year’s ecological disaster that killed swathes of marshland.

Some 10 hectares of mangroves and 35ha of salt marsh adjacent to the St Kilda Mangrove Trail has died since an adjacent salt mining company last year filled gypsum ponds with hypersaline water against the terms of its tenancy.

The water leaked through cracks in the pond’s lining and started killing the mangrove forest immediately, with experts warning there were signs of stress and dieback in a greater 193ha area.

Environmental expert Peri Coleman said pumping to remove the water was left too late, making it near impossible to remove the brine because the salt had started crystalising.

“So it was pushed up the hill within the pond to the landward side where it was allowed to evaporate and it deposited hundreds of thousands of tonnes of salt in those dams,” she told ABC Radio Adelaide.

“Of course, it’s rained since then, and the rain has picked up all that salt and brought it back down to the ponds closest to the mangroves.

Ms Coleman said she had already measured increased salt levels in the bottom of mangrove pools.

She said if the government acted swiftly, there was currently enough water in the salt ponds to pump it away into the miner’s pumping basins, “which the miner uses to dispose of waste brine into the Bolivar channel for dilution”.

Conservation Council SA chief executive Craig Wilkins said the rains were both a “blessing and a curse”.

“They increase the risk of poisoning, but they also mobilise the salt and provide an opportunity to pump it out as quickly as possible,” he said.

Community ‘should be heartened’

A Department for Energy and Mining (DEM) spokeswoman said it was continuing to monitor the site in conjunction with the Department for Environment and the Environmental Protection Authority and take “appropriate action as required”.

“The regulators’ actions are guided by strong science and monitoring program,” she said.

“The community should be heartened that the site has shown stability for a significant period of time, with no meaningful increase in the original area of impact.

“This shows the regulators have taken prompt and evidence-based action.”

But Mr Wilkins said he was frustrated by the government’s response to the latest leak. 

“The sun starts to dry up that salt and it starts to crystalise and pumping gets harder.

“They seem to be doing a lot of monitoring and lot of watching but no action.”

‘Inexplicably slow’ response

Opposition Environment spokeswoman Susan Close said the government’s response had been characterised by being “inexplicably slow”.

She asked recently in Budget Estimates how quickly an investigation being undertaken into the ecological disaster would be finalised.

“So we can make sure it doesn’t happen again, and they said not before the end of the year,” Ms Close said.

“This [dieback] happened more than a year ago.

“It feels like it’s an unfolding disaster occurring.”

The DEM spokeswoman said a “substantial update for the community on the health of the site underpinned by the best available science would be provided in the near future”.