The Environment Protection Authority took almost a year to issue a $1500 fine to energy company Santos over contamination of an aquifer near a major coal seam gas project, which included uranium at a level 20 times the Australian drinking water guideline for human health.

But the authority has defended the time taken to act and the size of the fine - which could have been as high as $1 million - arguing it immediately moved to establish there was no threat to human health or livestock.

The Bibblewindi ponds in the Pilliga State Forest. Credit:Dean Sewell

Fairfax Media revealed details of the incident on Saturday, the first confirmation of aquifer contamination associated with coal seam gas activity in Australia.

It has prompted a call from the NSW opposition for a memorandum of understanding signed by Deputy Premier Andrew Stoner to fast-track the project, in the Pilliga Forest, near Narrabri, to be torn up.