A leaking pond that contaminated an aquifer with uranium at levels 20 times safe drinking guidelines is still being used, despite coal seam gas operator Santos knowing it was faulty more than two years ago.

Santos eastern Australia vice-president James Baulderstone confirmed on Monday that Bibblewindi pond at the site in the Pilliga forest, in north-west NSW, was being used to store water from previous operations, which was produced from exploratory drilling into coal seams.

NSW farmers Ted and Julia Borowski (holding banner) protest against Santos' coal seam gas project near the Pilliga State Forest on March 3. Credit:Dean Sewell

Poor quality pond lining has been blamed.

The pond was decommissioned in December 2011 and new water is not being added.