Building on to an existing patio. I had to move a 4x8 shed backwards and am adding on where the shed previously was. Got in there with the bobcat moving dirt today and buried my tracks. It’s thick mud, not really wet just grey and spongey. My plan moving forward is to dig down about 3ft with mini trac, fill with rip-rap, then base on top. Never dealt with this kind of sub base before not really sure how to proceed. Any help greatly appreciated!