Centennial Coal plan to release more water into Sydney catchment will make pollution worse

Dr Ian Wright says the discharge point is the worst source of waste in the Warragamba drinking catchment he has ever seen.( ABC News: Lani Oataway )

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.

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.

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.

The water from this discharge point will flow from Wangcol Creek into the Coxs River, which runs into Warragamba Dam.( ABC News: Lani Oataway )

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.

Dr Ian Wright says the licence which allows Centennial to release the water isn't tough enough.( ABC News: Lani Oataway )

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.

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.

Dr Ian Wright is calling on the EPA to toughen up its licence.( ABC News: Lani Oataway )

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.

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".

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.

Tommy Wiedmann wants the water to be thoroughly treated before it's released down the Coxs River.( ABC News: Lani Oataway )

"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.