Except for any existing natural feature which is unsafe and the removal of which is required by the Department of Buildings to eliminate hazardous conditions, no site alteration may take place except as provided in this Section, inclusive.

No modification of topography shall take place within eight feet of a tree that is counted toward minimum tree credits pursuant to the provisions of Section 107-32 (Tree Requirements).

Within any zoning lot which is not a plan review site, tree removal shall be permitted in areas that do not contain designated open space, provided that such zoning lot complies with the provisions of Section 107-32.