FOUR landholders within Hume Coal's exploration permit zone have given permission for the company to drill on their land.

The company began "wireline" drilling in the area on May 12. Its exploration permit extended from the Belanglo Forest south to Exeter and east to the outskirts of Moss Vale.

Project manager Michael Cunnion said the company was planning to drill about 30 holes at various locations in the permit zone, six of which have already been done in Belanglo Forest.

He said the four landholders who had agreed to allow drilling on their properties were not in one location, but scattered across the permit area.

At least 20 more holes were planned, mostly on private property, but the locations have not been finalised as the company continues its negotiations with landholders.

Mr Cunnion said a number of landholders had bluntly refused to allow drilling on their properties.

The company would pursue alternative sites if landholders refused and he expected to have the first phase of exploration drilling finalised within 12 months.

If, by that time, they could not do all their drilling, the company would consider mediation as a last resort, which was legislated for in the Mining Act 1992.

Mr Cunnion said there could be more exploratory drilling after this phase to further enhance information about the quality of coal found.

The working space for an exploratory drill site covers an area of about 25m2.

Drilling could not occur within 200m of a primary residence or within 50m of a structure such as a shed or dam.

Containment tanks collected excess fluid during the drilling process, preventing it from reaching the ground.

The fluid and sediment were disposed of at a facility after the drilling was completed.

The hole made by the drilling is about 10cm in diameter at its widest point and got narrower as the hole got deeper.

When completed, the hole was sealed with concrete and capped.

Depending on weather, each drilling took five days - Monday to Friday. There was no drilling on weekends or at night.

The drill reached depths of up to 130m through the Wongawilli coal seam and into the Tongarra seam.

Geologists extracted core samples every three metres, which were sent away for analysis.

Mr Cunnion said the quality of the coal samples as well as results from water monitoring tests would determine whether the company would pursue its application for an underground coal mine in the future.