POISONOUS water could wash into the Murray-Darling because an opportunistic mining company is taking advantage of the NSW government's "piecemeal approach" to coal seam gas (CSG) waste water regulations, environmentalists say.
Despite the government banning evaporation ponds - which store chemical-laden water used to fracture bedrock to free CSG - the department of trade has allowed mining company Santos to build two "dams" in the Pilliga forest in northern NSW, the Wilderness Society said.
The "dams" have a capacity of 600 million litres and the water they will store contains arsenic, lead, chromium, salts and petrochemicals.
"It's really not just salty water like they say," Wilderness society campaign manager Naomi Hogan told AAP on Thursday.
The two mines are in areas that have recently flooded, Ms Hogan said, and if the "dams" are overfilled, water containing poisonous chemicals will be flushed into creeks that run to the Namoi River, which feeds the Murray-Darling.
"The arsenic and heavy metals in the water would certainly cause danger to any species that were to drink that water, any vegetation," she said.
"It's not drinking water standard this stuff, it's pretty nasty."
No plans have been developed to deal with an overflow of the "dams", Ms Hogan said, despite the risk and demands from the Environmental Protection Agency (EPA) and the water authority.
Santos plans to begin drilling at the site this year and Ms Hogan argues they been able to prepare the operation by exploiting the government's "piecemeal approach" to CSG waste water regulations.
Ms Hogan said the government body responsible for promoting mines, the department of trade and investment, is also tasked with approving them.
"It really is the fox in charge of the hen house," she said.
"They are pushing their own mining agenda at the expense of other input from Barry O'Farrell's supposedly strong and independent EPA, which is clearly being ignored."
Comment is being sought from the government and Santos.
