Dry stacking is the most sustainable method used to store filtered tailings — the silty, sandy material that’s left over once the metals are extracted. In the dry stack method, tailings are placed and compacted in a mound that is concurrently reclaimed with native soil and vegetation. There’s no need for a dam to hold them in place, no possibility of dam failure, and no long-term storage issues. What’s more, due to the deposit’s geology, the tailings will be non-acid generating.