The height above curb level of the street wall of any development or enlargement shall be as shown in the District Plan (Appendix A). In addition, the following provisions shall apply:

1. The street wall location provisions of paragraph (a) of Section 35-631 (Street wall location) shall apply to all street walls except that when a prevailing street wall frontage exists, the line-up provisions of paragraph (a) of Section 23-431 (Street wall location requirements) shall apply. For the purposes of applying street wall location regulations, all streets shall be considered as wide streets.
2. Street wall recesses are permitted below the level of the second story ceiling for subway stair entrances required under Section 118-50 118-30 (OFF STREET RELOCATION OF A SUBWAY STAIR WITHIN THE SPECIAL UNION SQUARE DISTRICT). Such recesses shall be no longer than 15 feet and no deeper than eight feet or the width or length of the relocated subway stair, whichever is greater.
   
   Street wall recesses are also permitted below the level of the second story ceiling for building or store entrances only.
3. On a zoning lot where there is an existing building to remain, the requirements governing height and location of street walls shall not apply within a volume defined by the rear wall of the existing building (W2), the front lot line (W1), the prolongations of the side walls (L) and a height of 125 feet above curb level.
   
   If, after January 10, 1985, any demolition or destruction occurs within the volume defined, the requirements governing street wall height shall apply.

EXISTING BUILDING VOLUME FOR
MODIFICATION OF STREET WALL REQUIREMENTS

1. The City Planning Commission may authorize modifications in the required street wall location if the Commission finds that the existing buildings, or existing open areas serving existing buildings to remain on the zoning lot, would be adversely affected by the location of the street walls of the development, enlargement or alteration in a manner prescribed in paragraph (c) of this Section.