Mike Klever sent this tip about the Layer Erase command, which he uses with AutoCAD Civil 3D Land Desktop Companion. "Most of us have had situations where layers just won't go away, even after you think you have erased all visible entities from that layer. By using the Layer Erase (YE keyboard entry) command, you can erase all objects on a chosen layer either by picking on an object from that layer or by hitting enter after initiating the command and picking the layer you want to erase from a list. Using Layer Erase does not delete the selected layer from the drawing; it just erases the objects that are on that layer.
"I find this command useful for cleaning up layers in drawings that are not needed coming from outside sources, thus saving time by erasing all objects from a layer with a single selection. I then use the purge (PU) command to remove all unused layers from the drawing file. This helps to reduce unnecessary xref layers in all drawings associated with it in the future."
NOTES FROM CADALYST TIP PATROL: In 2007 and 2008 the Layer Delete command (in the Layer Properties Box) and in 2009 (in the Layers Ribbon dropdown) will provide the desired results. The Tip Patrol did not locate such an alias (YE) for Layer Erase in Civil 3D 2009.