The NSW Planning Department ordered mining companies behind three applications to build new mines or expand existing ones around the village of Camberwell to produce more air quality data while the projects were stalled.

About the same time, the department received final reports from independent experts it commissioned to investigate the cumulative effects of mining on the village.

The Newcastle Herald understands the brake on the applications prompted at least one miner to voice concerns for jobs if the project was not determined soon.

The "cumulative impacts" study was announced in December 2008 to look at the effects mining operations on the fringes of Camberwell had on drinking water, air quality and noise levels.

It followed complaints from several village residents about "black sludge" in water tanks, respiratory problems, noise from trucks and blasting at the mines.

At the time of the announcement, the government said it expected the process would take about six months. But the results have yet to be made public.

The final expert reports were handed to the department in late May, when it also asked the three mining companies - Integra Coal, Ashton Coal and Ravensworth - to undertake further air quality modelling using environmental consultants PAEHolmes.

A department spokesman said the extra air quality information was requested from miners "to ensure that integrated modelling of all potential cumulative air quality impacts was available to the department, thereby allowing a robust assessment of the three proposals".

He said the department's assessment of other environmental issues associated with the projects had continued, while the extra information was compiled.

It is understood the department was given the requested information on July 1.

The project status of the applications on the department's website was changed from the unusual category "on hold" to "assessment" on Friday, after the Herald called the department.

Integra Coal told its workforce it needed the project decided by the end of July to ensure employment for contractors and, eventually, at least 70 full-time staff beyond the life of some of its existing operations.