St Kilda mangroves salt threat returns after rain, as SA Government investigation drags on
More than a year after an independent scientist alerted the authorities to problems at the St Kilda mangrove trail, no action has been taken against the company and the salt threat is edging closer after recent rains
SA News
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Heavy rain is mobilising salt on the surface of the disused evaporation ponds at St Kilda, threatening to cause more damage to saltmarsh and mangroves.
While residents, scientists and conservationists are keen to begin restoration work, they are worried that the source of the problem has not been addressed and are yet to find out if any action will be taken against the company Buckland Dry Creek.
More than a year ago, local scientist Peri Coleman, from Delta Environmental Consulting, alerted the authorities to the filling of disused ponds that leaked hypersaline water, killing at least 10ha of mangroves and 35ha of saltmarsh.
Now she warns further damage will be done, because summer pumping just moved salty water to encourage evaporation.
“So now it’s rained, all of that salt has redissolved, and the ponds are full of pink water again,” she said.
“Which is why we are saying, what’s the salinity in the groundwater bores?
“Because we’re pretty sure that you’re getting another slug (of saline groundwater) going through.”
The St Kilda resident took it upon herself to test the water near the mangrove trail yesterday as part of her daily exercise routine.
She said rain has dissolved the salt in pond PA6 next to the mangroves so the water gathering in that pond was now about 315g/L, strong enough to stop dissolving any more salt, and nearly strong enough to start crystallising.
“This will be leaking towards the mangroves in a second wave of hypersaline groundwater,” she said.
“In the saltmarsh pool at the boardwalk, the surface water was around seawater salinity at 39g/L, but at the bottom of the pool, the salinity is more than 45g/L. So there is measurable stratification still, and some indication that hypersaline brine is seeping into that pool.”
Dr Coleman said the Save St Kilda Mangroves Alliance has been frustrated by a lack of information from the State Government and feels the current investigation into the role played by the company is used as an excuse to refuse requests under freedom of information laws.
“It’s like pulling teeth, trying to get any information from the government and we have no idea where the investigation is going,” she said.
The Alliance believes the area affected has been underestimated because the State Government assessed only dead vegetation, rather than including plants that are stressed or dying. They want the extent of hypersaline groundwater mapped out as in suburban groundwater prohibition areas.
A State Government spokesman confirmed the investigation was continuing.
“The investigation into this complex issue is based on the highest scientific standards,” he said.
“Work continues to stabilise the site and allow the mangrove ecosystem in St Kilda to recover over time. Monitoring data is being independently assessed.”
Buckland Dry Creek was contacted for comment.
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