That was one of the questions put to AGL Group general manager for upstream gas Mike Moraza at a public forum in St Andrews last Saturday that ignited debate about local coal seam gas mining.

More than 60 residents and AGL employees packed out the community hall to hear speakers who included Mr Moraza, Greens Upper House MP Jeremy Buckingham, Macquarie Fields MP Andrew McDonald, Helen Redmond from Doctors for the Environment and Jacqui Kirkby from the Scenic Hills Association.

Campbelltown councillor Fred Borg was also there.

Mr Moraza did not directly answer the question, but reiterated the gas company's policy of "co-existence and compatibility" with the communities it operated in. During the two-hour meeting, many residents said they were concerned about the proposed expansion of the Camden Gas Project into parts of Campbelltown, including the Scenic Hills.

The plans, which propose 12 gas-well sites over an area of 38 square kilometres, are at present before the state government.

Mr Moraza said the Camden gas project was important because it supplied up to 6 per cent of the state's natural gas.

He defended the company's use of drilling techniques, hydraulic fracturing and water and chemical use.

"If AGL thought what we were doing was going to damage the water supply, we wouldn't do it," he said.

Both Dr Redmond and Mr Buckingham said they were concerned about coal seam gas mining and advocated a moratorium on the practice until further investigations.

But Mr Moraza said a moratorium was "completely unnecessary" and would shut down the industry.

Scenic Hills Association spokeswoman Jacqui Kirkby told the forum mining was incompatible with land use in the Scenic Hills.

"It is morally indefensible to foist this on a community when there are so many unknowns and the industry has not proved that it can operate safely and economically at the same time," she said.

Bow Bowing resident Martin Robinson said he was "unimpressed" with Mr Moraza's failure to give a direct answer to his question about why the expansion threatened the Scenic Hills.

"They can't even give you a straight answer," he said.