Backfilling is becoming normal in many jurisdictions, especially regions near significant developed areas. The reality is that a quick google search will show many open pit mines which are "not currently in production" and are not in any stage of backfilling, even in areas required by law. The bigger the gold system found is, the more years of mine production and the longer the company has to deal with the problem. There are other ways of dealing with the pit. I have visited an open pit iron mine which has been turned into a man-made lake and stocked with rainbow trout.

In my opinion, this is not something to worry about. Let's get a resource, a feasibility study and a mine and then we can talk about what to do when we have every ounce of gold out of the ground.