One month after the worst fish kill on record at Menindee, the NSW Environmental Protection Authority has confirmed it will investigate it as a pollution incident.
In March, about 20 million fish, mainly native bony bream, died after the oxygen levels in the Darling River plummeted to nearly zero.
The town, in the far west of the state, then watched in horror as the water body turned a sickly green when millions of fish corpses decomposed and sank to the bottom of the river.
The ecological disaster triggered a multi-agency response headed by NSW police and involved WaterNSW, Essential Water, the Central Darling Shire and the Far West Local Health District.
Now, one month after the major fish kills, the EPA has announced the catastrophic event would be treated as a "pollution incident".
The investigation will fully examine all potential causes, determine whether any pollution offences were committed and what regulatory actions need to be taken.
The investigation is expected to examine the role of individuals, companies and government entities.
Environment Minister Penny Shape said the investigation by the EPA would be separate to the independent inquiry promised by the state government.
"[The EPA] will do a separate investigation into the role of a variety of agencies and others ... i n terms of leading to the pollution that led to the fish kill," she said.
"It is a very important investigation and I welcome it."
The EPA was involved in the multi-agency response in the immediate aftermath of the fish kills.
The initial tests carried out were to examine whether any pesticides were involved.
But, after checking for more than 600 chemicals, none were detected.
Further testing has since been carried out with results expected to be presented to the community early next week.
Ms Sharpe said some Menindee residents were skeptical about the results of initial tests carried out by numerous agencies and urged patience for the final findings.
"The two responses to that really are; we are waiting on the final results from all of the testing to be available," she said.
"They will be made available and public in raw data, online as soon as they are available.
"The second part of the testing is making sure the testing regime is working well and is actually fir for purpose."
Water testing should be priority
Western Sydney University associate professor Ian Wright said he believed water quality testing should have been made a priority in the immediate aftermath of the disaster is
Dr Wright said he was "very critical" of the initial testing for pesticides but thankful a deeper investigation was now going take place.
"This fish kill on the Darling River is gargantuan," he said.
"It is without precedence and for the EPA to test six samples collected by a different agency six days after the fish kill is unbelievable to me."
Dr Wright has slammed the inaction of the EPA and its slow response to the disaster.
"Six samples? I would expect 60 samples in detail hours after the event and during the event," he said.
"It is great there is going to be an inquiry but we need data to go through and we missed some really important."
Long recovery ahead
Menindee resident Graeme McCrabb has echoed Dr Wright's sentiments, believing water quality testing should have been undertaken throughout the entire Darling River system prior to the fish kills.
"The thing the EPA need to step up to the plate with is the testing of water, not just here at Menindee but through the entire Darling system," he said.
"We don't have data going back a long, long time on water quality around pesticides and run off.
"it can't just be a here and now it has to be a consistent targeted approach to water testing right through the system."
Mr McCrabb said there was still a consistent number of fish dying and there was an underlying smell is the air sometimes.
He said the recovery period was still a long way off for the town and its residents.
