The structure of the Visonta open pit coal mine

There are three coal layers under the looze grit that needs to be removed first. The three layers of coal are also separated by spoil.
Spoil has to be deposited, at the Visonta mine it is simply dumped to the depleted side of the mine pit thus the valley is moving from one end to the over the coal seam, always only a few hundred meters wide space open, the rest is still covered by the spoil, or is depleted and is used to hold the spoil previously removed from the other side.