Miner in court after Blue Mountains spill

Dominica Sanda
AAP

Conservationists have welcomed a coalminer's guilty plea after the company spilled more than two thousand tonnes of coal material into the Blue Mountains National Park, but they're worried it could happen again.

A sentencing hearing is under way this week in the Land and Environment Court after Clarence Colliery was prosecuted by the NSW Environment Protection Authority for negligently allowing coalmine waste to pollute the world heritage-listed site in July 2015.

It will also respond to a second charge by the Office of Environment and Heritage over damage to the Blue Mountains National Park.

The company could be fined up to $2 million.

The 2015 incident involved the uncontrolled release of 421 tonnes of coal fines slurry and 1910 tonnes of coarse reject material.

Some of the mine waste made its way 10.3 kilometres down the Wollangambe River.

The EPA made 44 inspections to the affected side, while the clean-up took 51 weeks, with well over 600 helicopter trips to haul the coal materials from the river, the EPA said in a statement on Monday.

After the incident, Clarence Colliery, which has pleaded guilty to both charges, ceased all activities and was ordered to contain further pollution.

Clarence Colliery is owned by several companies with Centennial Coal owning an 85 per cent share, according to its website.

Blue Mountains Conservation Society president Madi Maclean says the spill occurred because the company failed to install floodlights, flow metres, level alarms, or ensure the integrity of structures containing the coal fines.

"While I am pleased to see that Centennial is in court ... I am disappointed there was no information on the changes to Centennial's management practices that would prevent this coal fines spill happening again at a Centennial coalmine," Ms Maclean said in a statement on Monday.