Use the FindSiteOverlaps command to locate overlapping (collinear) objects in the same site that could be causing problems with your drawing.
When creating site objects (alignments, gradings, feature lines, or plots), you may end up with collinear segments. In most cases, this will not create a problem. However, in some cases, Autodesk Civil 3D may close unexpectedly because of these overlapping segments.
If the FindSiteOverlaps command detects collinear segments, the command will recommend the usage of a subsequent command to resolve them. The FindSiteOverlaps command does not, however, diagnose exactly what may be causing a particular problem and the recommended commands may not resolve every possible issue you may encounter.
Anytime you experience problems with a drawing, you should use the RECOVER and AUDIT commands first before using the FindSiteOverlaps command.