Combined Surface for Multiple Pipe Trenches in Naviate for Civil 3D

When you have multiple pipe networks that all have their own shelf in the section, it is usually more work than it is worth to create a corridor for the whole section. The best way is to create individual corridors and then combine the solids or the surfaces later. In this post I will describe how to combine the surfaces to get a combined trench surface.
Combined Surface for Multiple Pipe Trenches in Naviate for Civil 3D