A water scientist is warning a Lithgow coal mine's plan to release five Olympic-sized swimming pools of "predominantly untreated groundwater" a day into Sydney's drinking catchment will make its pollution worse.
Key points:
- Centennial Coal wants to pump more water from its Angus Place Colliery into the Wangcol Creek
- The company says it will improve the quality of the current discharges, but an expert says it will make pollution worse
- The expert says it could be detrimental to the aquatic ecosystem
Centennial Coal has lodged an application with the NSW Department of Planning and Environment to pump 10 megalitres a day from Angus Place Colliery into the Wangcol Creek.
The plan would increase the average release into the waterway from roughly one Olympic-sized swimming pool a day to five.
The company's modification report said it needed to discharge the additional water, bypassing its water treatment plant, as the plant was operating at capacity.
"The ongoing inflows … [have reached] emergency storage capacity," the mine's planning documents said.
"Centennial Angus Place needs to urgently dewater the mine to manage the imminent risk of flooding.
"If flooding does occur, the mine may cease to be feasibly operated in the future."
The mine has been dormant since 2015, but Centennial has plans to reopen its operations under a new proposal called Angus Place West.
It said that project would secure the supply of coal to the nearby Mount Piper Power Station and safeguard the state's energy security until that plant's closure in 2040.
Energy Australia, which owns Mount Piper, said the water changes were essential for coal supply.
Elevated pollutants in mine water
According to the planning document, the water already released into Wangcol Creek has elevated levels of heavy metals like cobalt, iron, nickel, and zinc and is "predominantly untreated groundwater".
The planning document said diluting these flows with more water from Angus Place would result in lower concentrations of the contaminants and "improve" the water quality.
But Ian Wright, an associate professor in environmental science at Western Sydney University, said it would do the opposite.
"The actual mass, the physical amount of pollutants, is actually likely to increase," Dr Wright said.
"In the whole of the Warragamba drinking catchment that is the worst point source of waste I have ever measured."
Dr Wright said the salt, nickel, and zinc pollutants in the mine water were poisonous to aquatic life.
By his calculations, although less concentrated, the amount of salt would increase from roughly six to eight tonnes a day.
Although the concentration of nickel and zinc would reduce, he said they were likely to have a more significant effect on the environment due to the volume of water pushing it further downstream.
The predicted levels of salt, nickel, and zinc were well above what Dr Wright said was the widely accepted industry standard.
Environmental licence 'ineffective'
But Dr Wright did not point the finger at Centennial, instead blaming the Environment Protection Authority's (EPA) environment protection licence (EPL).
An EPL regulates levels of pollution released into the environment.
"It's allowing the coal mine to currently release very contaminated wastewater – and I don't blame them. The EPA has set the benchmark so low," Dr Wright said.
The licence sets limits for four contaminants, none of which include salt, nickel, and zinc.
It also does not set a limit for how much water the mine can pump out.
"That is one of the most ineffective pollution licences I have ever seen," he said.
The EPA declined an interview, but said in a statement it "looks forward to seeing improvements in the quality of discharge water into the catchment".
Food growers concerned about environment
Tommy Wiedmann lives downstream from the Angus Place Colliery on the banks of the Coxs River in the Kanimbla Valley.
He and his wife rely on its water to feed their vegetable garden.
"We do have a general concern about potential accumulation and potentially vegetables taking up some of these contaminants," he said.
"If it's a necessity to keep operating then there should be efforts made to expand the capacity of the water treatment plant in the shortest amount of time possible."
He said he was worried for the platypuses, waterbirds, and the rakali water rats that live in their bend of the Coxs River.
Dr Wright said treating the pollutants in the water would help protect those species.
"A pregnant or lactating female [platypus] will eat half her body weight every day. They need that invertebrate life which is so sensitive to the pollutants in this waste," he said.
WaterNSW said in a statement it would be "keeping a close eye" on any mine water releases and is providing advice about any associated impacts.
The authority assured its scientists use state-of-the-art modelling to make sure treated water from Warragamba Dam is safe to drink.
The plan, which is yet to be approved, is proposed to run until the end of August 2024.