3ds Max Modeling :: Smoothing Surfaces To Make Terrain Look More Natural

I often work with Civil Engineers and I use line work from Civil programs such as 3D Civil and Bentley MX. These programs give me splines (see image 1). I trace over the lines to create poly surfaces which may end up being grass or concrete etc (see image 2)

I don't use the terrain command because the command is not always suitable. The lines I import often have gaps or other issues thats why I find it faster to trace over the lines to create my poly surfaces.

But if you look at image 2 it's very blocky. I would like to smooth between these surface to make the terrain look more natural. I have played with turbosmooth and meshsmooth but sometimes they screw up the surface or don't work at all.

How I could make my surfaces more natural and less blocky.