Site flatten - top down

I am attempting to show/create an excavated hole in the ground.  The existing ground surface is in the 500-530' elev range the hole will be dug to a depth of 400' elev.  The excavation boundary at the surface is constrained to a defined boundary.  Therefore, the excavation needs to be inside this line.  Wall slope is 70 degrees.

I draw the area to represent the limits of excavation at the surface, select that area, then do the Calculate Flattened Site Plan Grid option.  The resultant grid surface is drawn such that GM apparently sets the boundary area at 400' and works it way back up (bottom up).  I need it to work top down as shown by the green line in the screenshot.

I've tried the various options and none will seem to do what I want.  Any recommendations?


  • sphillipssphillips Posts: 106
    GM flattens the area feature you select to the target elevation you set. Therefore you need to start at the bottom of the excavation and work up to the existing ground. I don't think you can get the excavation to match the exact footprint but you can certainly get it to fit within it.

    Potential workflow:
    1. Calculate the offset required relative to the excavation boundary for the bottom i.e. approx -36.4' 
    2. Use the Buffer tool to offset the excavation boundary by that value
    3. Edit the vertices of this new area feature to set them at 400'
    4. Use the Flatten site plan to create the slope up to your maximum elevation or higher i.e. 530'
    5. If the terrain strays out of the excavation limits then select the boundary and use it to clip the terrain using the Cropping tab of the layer
    If you have a questions give us a yell. Good luck.

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