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A-F. Examples of chambers and shafts backfilled with colored sand from other layers. Each example shows the chamber (or shaft) in general view, along with a detail at higher magnification showing the multiple colors of the backfilled sand, and a histogram showing the weight of each of the colors of backfill. These weights include the native sand contained in the mixture, but exclude the weight of the backfill originating in the host layer in which the backfill is located.
