One of the misconceptions I encounter in conversations about earthen building construction is understanding that dirt isn't just "dirt." There's good dirt and bad dirt, easy dirt and hard dirt, dirt with heavy clay, dirt with light clay, expansive, nonexpansive...and so it goes.
As retaining walls go up and foundation pads are prepared, our site crew hits a "gold mine:" a patch of fabulous looking dirt for block production a mere 3 inches under our deepest excavation to date. Having a site crew that knows dirt makes all the difference. In fact, this site crew has extensive experience in rammed earth construction. A few phone calls...dirt collection...test blocks and shazaam we realize that the best site dirt lies just where we want it between two building slabs.
This creates the opportunity to excavate the dirt we want, replace it with dirt that is not as optimal and not disturb our pad sites in the process. The goal, after all, is to build the building out of the earth it sits on!