Cameras have been sent through a storm water system that flows into the Adelaide Dolphin Sanctuary to investigate how arsenic and other heavy metals are leaking into the Port River.
The Royal South Australian Yacht Squadron has been calling for action on industrial pollution in the Port River and sanctuary since 2016.
It claims polluted water — containing arsenic, iron, chlorine and other toxins — is being pumped into its Outer Harbor marina through a stormwater drain underneath Coglan Road.
Squadron committee member David Eldridge said fish and dolphins have disappeared from the pool and native rats are turning up dead.
He said the squadron has spent $12,000 on commercial divers to remove two walls of silt build-up near the drain.
"The only time we get any effluent out of that pipe is when it's not raining and someone is pumping effluent into our marina," he said.
He said it was good Renewal SA was now "in the picture quite strongly" after a parliamentary committee started to investigate his concerns.
"It's too late for the dolphins that have died but we want to have this marina in pristine condition for the fish, for the dolphins, the native rats and the birds that feed here," Mr Eldridge said.
Sightings of the mammal in the sanctuary have dropped by 30 per cent in the past five years, and not one calf has lived beyond the age of three since 2019.
In a statement, Renewal SA — which owns Coglan Road — said the agency received a report in 2021 that dirty water was being discharged into the Port River by a nearby business.
"That business sits on private land meaning any onus of compliance is the responsibility of that business," a Renewal SA spokeswoman said.
"Port Adelaide Enfield Council and Environment Protection Authority staff visited the business, which subsequently implemented control measures to prevent inadvertent stormwater pollution."
But in response to continued pollution entering the marina, Renewal SA said it had employed a stormwater engineer to "map the drain's catchment" and investigate any potential contamination using cameras.
"Evidence of any potential environmental breaches will be referred to the EPA for investigation," the spokeswoman said.
She said Renewal SA may also install a "pollution trap" that would catch any pollutants before they hit the marina.
After years of failed attempts to raise the issue with Renewal SA, the council and the EPA, the squadron decided to make a submission to a parliamentary inquiry into the Port River dolphins.
The committee is currently investigating why members of the unique pod continue to die, and will get an interim report to government by next month.
Committee members Tammy Franks, Michelle Lensink and Sarah Game visited the marina late last month.
Ms Franks, a Greens MLC, said it had been interesting to see the difference between "what you're told by bureaucrats" and "what is really going on".
"The committee is helping to connect the dots and seeing that no one is taking responsibility — but no one has the ability to take responsibility," she said.
"It seems everything to do with this area is put in the too-hard basket because there's too many authorities involved."
Dolphin activist Mike Bossley estimates there are fewer than 15 Port River natives left, which he believes is about "half of what it used to be".
The council has told the inquiry that one major issue facing the Port River is confusion over which government department, agency or organisation is responsible for the water quality.
