You've been adding contour data to your surfaces for a while now. Did you know you've been doing it wrong? This post will show you what you've been doing wrong for ages as well as the correct way to add contour data to your surface.
Edit and Rebuild Surface in Civil 3D – Plex-Earth Support Desk
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Edit and Rebuild Surface in Civil 3D – Plex-Earth Support Desk
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Adding Contours to a Surface, You're Doing it WRONG