Land and Environment Court Justice Nicola Pain made the ruling against Sibelco for allowing up to five million litres of sediment laden water from its bentonite mine, near Parkville, to run into the waterway in May last year.

The pollution reduced aquatic life, temporarily damaged habitat along 2.8 kilometres of the brook and made downstream water undrinkable for at least a month.

Bentonite is a type of clay used for drilling oil and gas wells plus geological investigations.

A neighbouring landowner noticed sediment in the water and notified the New South Wales Environment Protection Authority.

The pollution resulted from part of a dam wall collapsing.

Environment authority officials took legal action and Sibelco representatives pleaded guilty in court to polluting.

Justice Pain ordered the company to pay $78,000 to the Hunter Central Rivers Catchment Management Authority to improve and protect the environment, instead of a fine.

Sibelco officials were also ordered to pay the protection authority’s legal and investigation costs of $35,000 and advertise details of the conviction in The Singleton Argus.

Sibelco removed sediment from the affected area, provided drinking water to affected residents and cleaned up Middle Brook to its condition before the incident.

When sentencing Sibelco, Justice Pain noted that company officials notified no-one of the discharge.

This suggested more could have been done to monitor the dam wall and have a system in place to deal with its possible collapse, she said.

Environment Protection Authority spokeswoman Lisa Corbyn said the case was an important reminder for mining officials that it was vital to have processes in place to monitor, identify and control environmental risks.