Me and my father are rebuilding a barn. we have stalls torn down. we found some mold that came from the clay holding in the moisture. how far down do we have to dig to make sure all the mold/nasty clay get out.
I have no idea but if you don't change how it was secured in the ground it will happen again. Maybe dig down some & see if you reach clean clay.
Maybe pour footers and use some gravel for drainage?