Goofs

On a few segments children are shown making drawings on the circular stairway with chalk. Colored chalks, pastel chalks, and sidewalk chalk (shaped into larger sticks and often colored), used to draw, are primarily made of gypsum. Gypsum is a mineral that must be mined.

It's stated several times that one form of criminal punishment is being sent "to the mines", so clearly the Silo is engaging in some type of mining.