An environmental engineer says Energy Resources Australia has finally realised the risks involved in uranium mining by spending $250 million on waste water management.

The company will start operating a brine concentrator in 2013 from its tailings storage pit in the Kakadu National Park, after the dam came close to overflowing last wet season.

Gavin Mudd, from Monash University, says it has taken too long for ERA to be forced into taking action.

"I certainly welcome the progress and I acknowledge that ERA is committing to a lot of things, but I think it's still too far into the future. We need it more urgently than that."