The requirements set forth in Sections 33-45 (Tower Regulations) or 35-64 (Special Tower Regulations for Mixed Buildings) for any building, or portion thereof, that qualifies as a "tower" shall be modified as follows:
(a) At any level at or above a height of 85 feet above curb level, a tower shall occupy in the aggregate:
(1) not more than 40 percent of the lot area of a zoning lot or, for a zoning lot of less than 20,000 square feet, the percent set forth in Section 23-65 (Tower Regulations); and
(2) not less than 30 percent of the lot area of a zoning lot.
However, the highest four stories of the tower or 40 feet, whichever is less, may cover less than 30 percent of the lot area of a zoning lot if the gross area of each story does not exceed 80 percent of the gross area of the story directly below it.
(b) At all levels at or above a height of 85 feet from curb level, the minimum required setback of the street wall of a tower shall be at least 15 feet from the street line of Broadway or Columbus Avenue, and at least 20 feet on a narrow street.
(c) In Subdistrict A, the provisions of paragraph (a) of Section 35-64, as modified by paragraphs (a) and (b) of this Section, shall apply to any mixed building.
For the purposes of determining the permitted tower coverage in Block 3, as indicated on the District Plan in Appendix A of this Chapter, that portion of a zoning lot located within 100 feet of the west street line of Central Park West shall be treated as if it were a separate zoning lot and the tower regulations shall not apply to such portion.