Editing Surface in Civil 3D

I've got an existing surface created in Civil 3D and I now need to depict a new surface, which will include an excavation for some building foundations. I am relatively new to the program and am having a very difficult time determining how to show this new surface. I know the dimensions and depth of these excavated pits but cannot get the program to create a new surface that reflects these future digs. Any advice?

You will likely want to look into feature lines for this. Draw feature lines depicting your foundation. Create a surface and add the feature lines to the surface as breaklines.

Thanks, I'm well on my way en lieu of that advice, however, is it possible to change the grading style that is automatically implemented when pasting one surface into another. What I am attempting to do is create a basement footprint into an existing surface in such a way that the drop from existing surface to basement surface is abrupt. What I am getting instead is a gradual, very shallow grade from the basement surface up to the existing surface. Any advice?

Thanks

You can chnage the batter slope to a small value say 1 : 0.001

Alternativel create 2 polylines and set the elvation to basement level the second slighty offset 1mm if metric and make its elevation well above the surface make a new surface model (defintiom autocad objects)

The simply add a third surface copy and paste natural to this 3rd surface then copy and paste 2nd surface you should have now have what you want