I advised this to someone recently which reduces the steps:   1. Duplicate the layer the Site Model is in for safekeeping the original Existing Site Modifiers (just in case, for reference). 2. Go to a 'Top' view and change the Existing Site Model to be viewed as 3D Contours. 3. Ungroup. These 3D polygons now include the shape of the modified existing terrain. 4. Select them all and use them as the source data for a new Site Model.   Then there'll be no conflict
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