The incident occurred on February 1 and 2 last year (2012) when sediment-laden water was discharged from the mine’s western boundary, adjacent to Charlton Road.

The water then entered a drainage channel, which ran into Salt Pan Creek, Newport Lagoon, Wollombi Brook and then the Hunter River.

The company pleaded guilty in the Land and Environment Court and was convicted of breaching section 120 (1) of the Protection of the Environment Operations Act 1997.

In addition to the fine, it was ordered to pay legal costs of $51,000.

A Coal & Allied spokesman said sediment and erosion controls were in place at the time of the event but were unable to contain all the water deposited during the rainfall event.

‘‘Coal & Allied regrets that during a heavy rainfall event in early February 2012, non-mine affected water containing soil from civil works associated with the erection of a visual bund (as required under Mt Thorley’s Approvals), exited Mount Thorley Operations’ western boundary and flowed into land owned by Coal & Allied,’’ he said. 

“Coal & Allied has undertaken further works to improve its erosion and sediment control measures at Mount Thorley with more than $500,000 invested in measures such as water channels, sediment controls barriers and enhanced monitoring.”

Bulga-Milbrodale Progress Association spokesman John Krey said the fine was appropriate.

‘‘This was a major pollution incident and it’s good to see they have been held to account,’’ he said.

‘‘Mines have to pay more attention to their controls; they are too slack when it comes to dust and noise and now we have seen a serious water pollution incident as well.’’

The Land and Environment Court also ordered Coal and Allied to advertise the breach in newspapers today (Tues, Aug 26).