Again, for the purposes of a plan of this type, we tend to completely ignore the Z values except for surveyed points and points tied to a surface. In lieu of having a surface, "contour" lines may have an elevation attached for reference, but this tends to fool others into thinking they have more accuracy than the actual plus or minus 1/2 of their interval we are telling them it has. A Z value is not really considered unless we get a clue such as a non-continuous linetype not appearing correctly, failure to fillet or intersect or an errant offset. Since we do not intentionally enter a Z value in the linework it is almost always a byproduct of drawing line between points of different elevation. Surveyors can be very prolific with their points and it is often necessary to turn the elevation value off while creating linework due a congested area. Some of these lines get missed and when they cause an obvious problem they are corrected . . . often we never even notice. More massive distortions happen if one of these entities is used as part of a relative move, copy, mirror or rotate, but again it only affects Z values that we just don't think to check for. If found, a flatten utility such as Joe provided serves quite well to solve any problems as does a series of changes to all entities in the properties box. I think it is grand that you have a found such a use for these Z values for all of your linework and that they make your work so much more accurate and efficient. For my need on a plan such as this though, they are at best a nuisance and as we can see here, a real obstacle. I can honestly count on both hands every time I recall needing to type in a Z coordinate while constructing or editing my linework during my 31 years of this work.
The 2D locations your are so ready to dismiss along with the 3D drivel however is normally placed either painstakingly point to point from surveyed data using instruments capable of accuracy of the level of 1:15,000 or generated by the design program itself completely bypassing the technician. The X,Y AND Z values for surveyed coordinates of these points are displayed to 4 decimal places and if you are getting a Z on the linework, you can bet your keester the node osnap was being used at the time. The 2D is accurate if the drawing is created by anyone even half trying to do their job. It is actually more difficult to NOT generate the linework correctly for 2D purposes.
I call BS on your Luddite slur. What earthly purpose would there be in making a leader and chunk of text at a Z value accurate to 2 decimal places when any design change can render the value invalid. The purpose of a spot elevation is to GRAPHICALLY represent the surface elevation at a certain point, not something to pick on to check if it numerical value matches its Z coordinate. There is no time available in project I have worked in to waste in this manner.
When you inquire a distance between two points do you not get both a 2D and a 3D value? Use the 2D number and unless you are working on a whopping slope you will get a good number. Most all of the pipes out in the yard come in 20 lengths and are usually estimated on the number of said lengths will be needed since there is only one joint per each and any trimmed will be waste. You will be close enough.
The dimension that I said would be needed would be from a good corner off of YOUR plans. It would be up to me to worry about the accuracy of the plans you provided, verify your data, determine if we are using the same vertical and horizontal datum and rotation, and decide at what point to safely make your inch units match my foot units.
