TWO spikes in water contamination levels from a Territory uranium mine did not breach environmental regulations because the company uses different samples as its benchmark.

There are renewed concerns about Ranger uranium mine in Kakadu after conservation group the Environment Centre NT this week released data showing a spike in contaminated water flowing into Kakadu's Magela Creek from a leaking dam.

The company, majority owned by mining giant Rio Tinto, defended the spike of five times the warning level of electrical conductivity, saying it was due to salinity and was not dangerous.

The Supervising Scientist Division is the authority charged with protecting the region from the effects of uranium mining, and went before a budget estimates hearing in Canberra on Wednesday.

Its head, Alan Hughes, said there was no evidence the mine was having ill-effects on Kakadu, adding ERA was working on the dam leak, and had a funded plan to clean up the site when its operation ends.

Mr Hughes said his own monitoring showed the recently revealed spikes were magnesium sulphate and no other contaminants of note.

He said legal contamination thresholds were based on weekly "grab'' samples, even though continuous monitoring was ``much more sensitive and much more effective''.