Almost 270 million tonnes of coal will be extracted, of which about 160 million tonnes will be exported through the Port of Newcastle over the next 30 years. 

In recommending approval the commission urged the government to do more to protect the agricultural soils of the Liverpool Plains.

‘‘The commission considers it will be important for the government to undertake some more detailed work to identify and protect those highly valuable, fertile black soils where mining should be prohibited, as ongoing uncertainty for the surrounding community does impact on its ability to plan and invest for the future,’’ the commission’s report said.

Watermark was one of the first NSW coal exploration areas to return major sums to the state government, with China Shenhua offering a reported $500 million - including $200 million if a mine was approved - in 2008.

The mineral resources minister at the time was the disgraced former Labor MP Ian Macdonald.

Greens mining spokesman Jeremy Buckingham condemned the National Party for failing to some of the country’s most valuable farming land.

‘‘The Nationals came to power four years ago promising to protect strategic agricultural land from the threat of mining, but this approval shows they have comprehensively failed,’’ he said.

‘‘If the NSW Nationals and federal Agriculture minister Barnaby Joyce can’t protect the most precious farming area in NSW and their political heartland, then what use are they?’’

The commissioners said they agreed with many applicants who argued that the project’s public benefits had been overstated. 

However, they said significant employment, royalities and other economic benefits would flow from the project. 

‘‘In balancing all of the issues, the commission has given particular consideration to how the environmental impacts could be managed to ensure the sustainability and growth of the agricultural sector,’’ the commissioners said in their report.