Edit a Terrain Model Boarder

Hello,

Using Geopak Civil Engineering Suite SS4.   I have a Terrain Model that was survey-generated by the survey data we imported.   I am in the process of doing some cleanup and want to pull my terrain model boarder edge in or clip it out, to go around the edge of a building.  Currently I have triangles crossing through a area that shouldn't.   Is there a easy way to pull the boarder in?.    I don't want to turn off terrain model rules, since (as far as I know) all of my other changes will revert back to when I originally imported my data.  Attached is a screen shot of the area.