I got this question over the weekend and thought it was worthy of a post here on the Forum. The user stated that they had a "Finished Grade" model from the Engineer and an Existing Ground from the Engineer. They used the Merge Surfaces Command to Merge the "Finished Grade" into the "Existing Ground" to create a nee surface called "Merged" . They used the setting Finish replaces Existing in the Merge command.
After the Merge was completed the Exiting Ground outside of the Finished Grade Area no longer matched the Initial Original Ground Surface - the slopes were "off" when you reviewed the results in the Cross Section Editor in relation to the alignment for the project. Below is one of the screen grabs that they sent through to me for review.
The Magenta Line is the Finished Grade, The Green Line is the Existing nd the Red Line is the Merged Surface - so beyond the limits of the Finished Grade surface you would expect the red and Green Lines to Match however they do not - why is that and what is going "wrong here"
See the response below for the answer - this opened up a range of points that I think are worth clarifying here.