In all subdistricts, for street walls with widths exceeding 200 feet, a minimum of 20 percent and no more than 50 percent of the surface area of such street walls above the level of the second story, or a height of 30 feet, whichever is lower, shall either recess or project a minimum of three feet from the remaining surface of the street wall. Any such recess or projection shall be considered a permitted obstruction into a required setback, and the depth of such recess or projection shall not exceed three feet.

In addition, in Subdistrict D, the underlying dormer provisions of paragraph (c) of Section 23-623 shall be modified for portions of buildings facing Third Street, so that above the maximum base height, dormers shall be permitted only within 75 feet of the intersection of two streets.