For the purposes of applying the provisions of this Section, a “tower” shall be any portion of a building or other structure that is located above the maximum base height. Such portion of a building or other structure shall be subject to the following requirements:

1. Maximum tower widths
   
   Along the shore public walkway, the maximum width of a tower, or portion thereof, that is located within 110 feet of the pierhead line and facing the shore public walkway, shall not exceed 100 feet. Such width shall be determined by drawing perpendicular lines in plan view from the pierhead line to the outermost extents of the street wall of such tower, or portion thereof, within 110 feet of the pierhead line, exclusive of any permitted projections and dormers. However, in Subdistrict A, where the depth of a zoning lot, or portion thereof, is less than 220 feet, the maximum width of a tower within such shallow lot portion, shall not exceed 130 feet, provided that such depth was in existence both on December 10, 2020, and on the date of application for a building permit.
   
   Along all other streets, the aggregate width of street wall in a tower shall not exceed 250 feet.
2. Tower top regulations
   
   For all zoning lots in Subdistrict A, and for each portion of a zoning lot in Subdistrict B, bounded entirely by streets, as such term is defined in Section 127-20, the following requirements shall apply:
   1. Where two or more towers are provided and any portion of such towers exceeds 175 feet, a height difference of at least 20 feet, or two stories, whichever is less, shall be provided between such towers.
   2. Where any portion of a tower exceeds 175 feet, the highest two stories shall not exceed 90 percent of the gross area of the story located directly below such stories.
3. Maximum tower height
   
   The maximum height of a building or other structure shall be determined in accordance with the provisions of Article VI, Chapter 1 (Special Regulations Applying Around Major Airports), except where modified by certification of the Chairperson of the City Planning Commission pursuant to Section 127-236 (Certification to modify maximum height of building or other structure).
4. Additional requirements within Subdistrict B
   
   Along Janet Place, where a sidewalk widening is required pursuant to Map 3, the width of each individual tower portion located within 50 feet of the street line of Janet Place shall not exceed 70 feet, exclusive of any permitted projections and dormers. Such width shall be determined by drawing perpendicular lines in plan view from the street line to the outermost extents of the street wall of such tower, or portion thereof, within 50 feet of the street line, exclusive of any permitted projections and dormers. Such tower portion and any other such tower portion within the same or an abutting building shall be separated by at least 40 feet.