Hi can anybody help ive been given a job to find total cut and fiil on a site. I have been given a DWG topo survey of existing ground conditions. I have also been given a DWG of proposed levels. Both are in 3d so to do a cut and fill is easy just compare both serfaces. The problem i have is i have been asked to remove existing conditions from topo eg Topsoil =350mm,Tarmac =240mm how do i lower the topo DWG to accomadate these thicknesses. I have uploaded topo survey for ref thanks uploads/342286/HAN_STOKE_TOPO.dwg 

First create the surface from the Existing ground 3d cad file. After creating surface you could edit it by lowering it or lifting it from "Edit surface" tab on selecting the surface.