GROUND LEVEL

means: the actual finished surface level of the ground after the most recent subdivision that created at least one additional allotment was completed (when the record of title is created); if the ground level cannot be identified under paragraph (a), the existing surface level of the ground; if, in any case under paragraph (a) or (b), a retaining wall or retaining structure is located on the boundary, the level on the exterior surface of the retaining wall or retaining structure where it intersects the boundary.