I am trying to dig out the terrain for elements that are below the surface, in residential design this would be your basements, in this case it happens to be in ground tanks, the issue is that you can not do simple straight down cuts, the terrain change ends up being far too smooth which becomes and issue.
What this means is either you have the terrain bleeding through into your underground element, or there is a trench along the outer wall of your building.
There needs to be like a building pad option to cut straight down to a given elevation, or even better would be to auto detect the floors and push the surface down around them. What is a good workaround for this as using the flatten tool with a small radius would take DAYS.
I have also asked for more sculpting tools as these are a joke for demonstration only and not real manipulation.