BHP Billiton said its Illawarra Coal division continued to undertake an organisational review in response to the company's ongoing focus to ensure competitiveness and viability of the business.

Illawarra Coal asset president Troy McDonald said the company had advised employees and contractors about the review and the impact on some roles in the business.

"We will work closely with those who will be affected and provide the appropriate support services," he said.

"These workforce changes are essential to secure the future competitiveness of our business and will ensure we have the right number of people doing the right work to support our operations."

Initially, there will be 36 employee and contractor roles affected.

The next phase of the review will involve the operational activities and the full review will be completed by June 30, 2014.

"Illawarra Coal will treat all employees fairly and with respect and ensure that they are kept informed throughout the process," McDonald said.

For the three months to December 2013, Illawarra Coal's production was 1.9 million tonnes, after a horror September quarter in which production fell down to 1.4Mt due to a scheduled longwall move at West Cliff and an extended outage at Dendrobium.

BHP Billiton's $845 million investment in Appin Area 9 in NSW - which maintains Illawarra Coal's production capacity with a replacement mining domain and capacity to produce 3.5 million tonnes per annum of metallurgical coal - is on track for completion in 2016.

Earlier this week BHP Billiton revealed it would work on developing an environmental impact statement for its Caroona coal project after submitting a plan with the NSW government that proposed an underground mine that would not impact agricultural productivity in the area.

The mine is expected to yield up to 10Mtpa of saleable thermal coal over 30 years, with production being capped at 260Mt over the life of the mine.

The mine plan is part of BHP Billiton's Gateway submission to the NSW government, which is the first step in the mining approvals process.

The submission will also include a preliminary assessment of the potential impacts of the project on the agricultural values of the land.