The Tagebaurekultivierungsaktivitäten have been going on for a long time. I remember visiting some former open pit in the 90s, as they started filling it, noting how it would take like 10 years or so. Pretty strange land.

10 years? That's nothing. Flooding Hambach will take approximately 40 years. And that includes water from the Rhine carried there by pipeline, which in the current state of the Rhine is... optimistic.