Here are the steps:
Once the breaklines have been modeled and are ready to be added to a surface, adjust the Supplementing Factors in the Add Breaklines dialog box. The following settings work well but adjust them as needed.
• Turn on and set the Distance to 10.00’.
• Set the Mid-ordinate Distance to 0.01’.
Below are the links explaining the Supplementing Factor Distance and Mid-ordinate Distance from Autodesk’s Help file.
Autodesk Civil 3D Help: Supplementing Factors
Autodesk Civil 3D Help: Mid-ordinate Distance
Below are images of a surface with the default settings.
Let me know if you have any questions.