In addition to any use modifications which may be granted under the provisions of Section 105-701 (Applicability of large-scale residential development regulations), the City Planning Commission may permit semi-detached or attached single-family residences in R2 Districts and attached single- or two-family residences in R3-1 Districts.

Furthermore, except in the Special Natural Area District-1 (NA-1), the Commission may permit semi-detached or attached single-family residences in R1-2 Districts provided that the development or enlargement is on a tract of land of at least four acres, and provided the Commission finds that:

(a)        the preservation of natural features requires the permitted development to be concentrated to the extent feasible in the remaining portion of the tract;

(b)        for such concentration of development, better standards of privacy and usable open space can be and are achieved under the development plan by inclusion of the proposed residential building types;

(c)        the change of housing type constitutes the most effective method of preserving natural features;

(d)        the aggregate width of street walls of a number of residential buildings separated by party walls shall not exceed 100 feet;

(e)        the proposed street system for the tract of land to be developed is so located as to draw a minimum of vehicular traffic to and through streets in the adjacent area; and

(f)        the existing topography, vegetation and proposed planting effectively screen all attached single-family residences from the lot lines along the perimeter of the tract of land to be developed.