Here is the listed of undocumented commands from Autodesk to resolve site issues such as overlapping objects.
When creating Site objects (using Alignments, Grading, or Parcels), you may end up with overlapping segments. In most cases, this will not create a problem. However, in some cases, you may experience drawing instability or AutoCAD® Civil 3D® may crash because of these overlapping Site objects. Some of the problems with grading in particular may appear to be general instability—such as a crash on regen, save, or AUDIT—where it isn’t easy to see which object caused the crash.
Important! These commands are not tools for general grading troubleshooting; they provide a potential solution for specific situations. If you submit a Customer Error Report with your email address, and the conditions of your issue are likely to be resolved by using these tools, an automated message will be sent to you referencing this technical solution. Please make a copy of your original drawing before running these commands if possible.
Anytime you experience problems with a drawing, you should always try using the RECOVER and AUDIT commands first. (For detailed information on these commands, refer to the product Help file.) If this does not resolve the issue, continue with the following suggestions:
Note: The following tools are only available if you have installed AutoCAD Civil 3D 2009 Update 2.1 or a later version. You can use them to find and isolate overlapping (colinear) objects belonging to named Sites. They do not, however, diagnose exactly what may be causing a particular problem. Furthermore, they will not resolve every possible issue you may encounter.
To run, enter each command on the command line. These commands are not case-sensitive.
Start with this command, which will check for overlapping alignments, feature lines, and lot lines in a Site. A dialog box will be displayed, prompting you to select the Site to check. This command will mark any overlapping locations found with AutoCAD points, placed on the layer _OVERLAPPING_SEGMENT_LOCATIONS.
Note: To see the AutoCAD points better, you can use the DDPTYPE command to change the visibility settings if necessary, which will force a Regen. However, in cases with unstable Gradings or behavior a Regen may result in a crash.
Press the F2 button to review the command line. You will see the result of the check, and it will tell you which of the following commands to use to remove the overlaps.
Once you have performed the first set of recommended corrections, erase the AutoCAD points that were created and then run the AeccFindSiteOverlaps command again to see if any overlaps remain.
This command will move each overlapping feature line to its own individual Site, with the name "Overlap X" (Overlap 1, Overlap 2, and so on.). This command will not remove feature lines that use grading criteria. The thought here is that feature lines used simply as breaklines will be removed to separate sites but can still be used to create surfaces. Feature lines created from Survey data will only be included if they are part of a named Site.
This command moves alignments to the Alignments collection in Prospector. The alignments will no longer be part of the Site, but their names will be maintained.
This command performs the same function as AeccRemoveDupFeatureLines command above, except it will move overlapping parcel lot lines to separate Sites. It operates on the linework, not the parcels themselves, so removing some of the parcel linework to its own site may either create new parcels or remove existing parcels (a similar effect to moving the lines with the Move to Site command).
Additional tip: If, after removing any overlaps that can be found, there are overlaps reported for gradings, it may be possible to edit the gradings slightly so that they no longer overlap. For example, one case that may cause problems is when two grading footprints touch each other at a point where the grading projection lines overlap. In this case, the appropriate fix would be to remove the gradings and join the footprint. Use a single transition at that point instead of having two adjacent gradings.