We just built a house and the builder used "sandy loam" to fill.  Fortunately, the dirt from our septic field was used first so we only have about 4 inches of loam until you hit native dirt. The loam used is pink (horrible from what I gather) and not the dark brown/fertile stuff. Our native dirt is clay.  So Im thinking of tilling it to 8-12 inches and adding compost.  The question: how much compost and what type?