The chemical company Orica has been fined $768,000 over a series of chemical spills and safety breaches at two of its sites in New South Wales.

The NSW Environmental Protection Authority (EPA) took the company to the Land and Environment Court for breaching its licence conditions.

Orica pleaded guilty to nine charges.

In the most serious incident homes at Stockton near Newcastle were showered with the toxic chemical hexavalent chromium in 2011.

The Environmental Protection Authority says Orica was too slow to notify it about the leak.

In another incident a few months later emissions of ammonia, also from the Kooragang Island facility, resulted in two workers on a neighbouring industrial site being taken to hospital.

There was also an incident at Orica's Botany Plant in Sydney's south in late 2011, which resulted in mercury vapour being emitted.

The EPA said the incidents resulted in pollution being released into the air and water near both sites.

Environmental regulator 'pleased with outcome'

The EPA's chief environmental regulator Mark Gifford said the fines should serve as a strong deterrent.

"The Environmental Protection Authority is pleased with the outcome today," he said.

"It does represent a significant penalty for Orica for a series of events that really did concern the local communities, particularly in Newcastle, but also at Botany and three quarters of a million dollars is a sizeable penalty."

The money from the fines is to be spent on health and environmental projects in the Hunter and at Botany. Orica will also have to publicise its failings.

Mr Gifford said the EPA conducted a significant investigation into the incidents and he believes Orica has learnt lessons.

"We've certainly seen a change in Orica's attitude and improvements, particularly in the way they operate their site at Kooragang Island," he said.

"Orica has indicated they have invested over $200 million in upgrading and fixing that plant to ensure that it continues to perform adequately. And the EPA is undertaking a very rigorous oversight of those activities and will ensure its environmental performance continues to stay positive."

Orica said it will closely review the decision.

Orica's executive global head of manufacturing, Richard Hoggard, said the company regrets the events that took place.

"Today we have an opportunity to assess the progress Orica has made since 2011 and look ahead to further enhancements. We believe that Orica has come a long way," he said.

"The company has invested more than $200 million over the last three years delivering the largest improvement program in the KI facility's 45-year history. This is in addition to our significant investment in our people, processes and the community."

Cathy Burgess from the Stockton Community Action Group said she hopes the outcome will make a difference.

"For Stockton residents it's always been about safety and our concerns about that and I don't know whether them getting a fine will actually improve that," she said.

"We wanted better notification of when an incident occurs and we want to know that there's an emergency plan in place in case something does go wrong and we still haven't really seen that."