How do you show a topography of what has been excavated

[djn9SY84]

Hey Guys,

In the existing topography shown below I excavate for new building platforms. 

I want to show a topography surface of what has been removed. How do you do that? I tried duplicating the existing surface and cutting it by the new one. 

I want to be able to show the amount of surface that has been removed and apply a level gradient 

showing how many mm of surface is being removed. 

 

 

[RDAOU]

Not entirely sure what you are trying to do or at least it is not clear to me. I suggest to try use grading