AGL ENERGY says there are no negative effects on the air surrounding its Rosalind Park Gas Plant despite admitting it failed to properly monitor the site for the past three years.
In a statement last week, the company revealed it had breached the conditions of its environment protection licence by not monitoring the plant's gas emissions regularly enough.
It is believed monitors on the Menangle mining plant's exhaust stacks became erratic and failed in 2009 and were not replaced.
Instead, AGL carried out only quarterly monitoring at the site, which is part of stage two of the Camden Gas Project.
Continuous air monitoring is used to ensure gas emissions do not exceed the allowable limits.
AGL said senior managers learned of the error during an internal review and notified the Environmental Protection Authority.
Scenic Hills Association spokeswoman Jacqui Kirkby said the organisation was deeply concerned by the oversight.
"Who knows whether it's a cultural attitude there or incompetency," she said.
"But it [went on] for three years and no-one picked it up.
"Despite a massive failure of the system to monitor the coal seam gas industry, AGL is now being allowed to engage its own consultants to self-investigate and self-report.
"We are not convinced by assurances from AGL's consultants that cars are a far greater polluter in the Campbelltown area than industry."
Ms Kirkby said plans and submissions for the Project's proposed northern expansion, affecting parts of Campbelltown's western hills, were still being reviewed.