It comes as the mine further explores its underground Ranger 3 Deeps project after receiving approvals for a prefeasibility study earlier this year.
ERA is now backfilling its Three Deeps pit after it extracted the last of the ore from Pit 3 in the last week of November, several weeks ahead of schedule, the company says.
Tim Eckersely, ERA's general manager operations, stated that "mining performance this year has been very pleasing, our teams worked safely and efficiently to dewater the pit following the wet season so we could gain access to the high grade ore at the bottom".
He went on to say "work on backfilling the pit has now started, with the first phase of these works expected to be completed by the end of 2014.
"During this time, 30 million tonnes of material will be backfilled into the pit as an important part of ERA's ongoing rehabilitation program."
ERA started uranium mining in 1980, with mining in Pit 1 completed in late 1994; development of Pit 3 started in 1996 and mining of the orebody in 1997.
From 1997 to 2011 around 67 000 drummed tonnes of uranium oxide was produced.