You may wish to review my AU presentation....back in 2008.
Leica Topcon and Trimble Oh My. It goes into detail on how to use User Defined property classifications, survey database extended properties and the example used is Sewer manhole rims and inverts.
How to automate the import of measure downs from data collected points and automated the rim and invert labelling.
AutoCAD - Civil 3D - Map 3D - ESRI - Google
AutoCAD Civil 3D Implementation Expert