1. Start a new Civil 3D drawing using your company’s standard template then save the drawing to the project folder.
2. Data reference pipes, proposed and existing surfaces into the new drawing file.
3. Set the Existing Grade surface to a No Display style.
4. Create a new existing surface and name it Existing Surface for Navisworks and set the display style to a TIN (Triangular Irregular Network).
5. Paste the Existing Ground surface into the Existing Surface for Navisworks. (This will allow a hide boundary to be added to the surface.)
6. Set proposed surface to display as a TIN (Triangular Irregular Network).
7. As you can see the existing surface TIN overlaps the proposed TIN in the cut areas.
8. Extract the boundary from the proposed surface by
1) Clicking on a proposed surface.
2) Click Extract Objects from the Surface Tool Panel of the Ribbon.
3) Uncheck everything except the Border objects.
4) Depending on Civil 3D drawing styles, the border will be extracted to a designated layer.
5) Repeat steps 1-3 for each proposed surfaces.
Note: The boundary will have to be re- extract when the proposed grade is updated.
9. Add the extracted borders to the Existing Surface for Navisworks as Hide boundaries.
10. Repeat step 9 for each proposed surface.
11. As you can see, the existing surface is no longer overlapping the proposed surface.
12. Export the model to Navisworks by typing NWCOUT. Save the file to the project location. I named the file Export to Navisworks.nwc.
13. Open the Export to Navisworks.nwc file in Navisworks and use 3D Orbit to view the site, pipe networks under the surface and other Navisworks tools.
Here is a quick animation from Autodesk Navisworks 2012 of the site.