i have seen one in use, the wall was put together on site, the wheel on top is the tricky part, especially lining up the roof supports with the wheel.

yup, realized that as soon as hit submit

after you are done the same amount of dirt would be replaced, very minimal divoting. kind of like the law of conservation.

you could build a dome, and excavate the interior for a below level pit, then adobe the outer walls with the dirtpile. :? almost like a sphere on the inside a 12' diameter circle could give that much spherical volume with only a minimal amount of work, one little u-haul could yield you almost 7000 c...