A sky exposure plane of 2.5 to 1 shall begin at a height above curb level of 125 feet on all streets within the Special District, except that on a narrow street beyond 100 feet from any street line opposite a public park or from the intersection of such narrow street with a wide street, the sky exposure plane shall begin at a height above curb level of 85 feet. No development or enlargement shall penetrate such sky exposure plane except pursuant to Section 33-45 (Tower Regulations). However, Section 33-45 shall not be applicable to any portion of a building located within 100 feet of a street line opposite a public park. In addition, energy infrastructure equipment and accessory# mechanical equipment shall be permitted obstructions above such height limits, subject to the provisions of Section 33-42 (Permitted Obstructions).

For qualifying affordable housing or qualifying senior housing, the height and setback provisions of Section 35-652 (Maximum height of buildings and setback regulations) may be applied as an alternative as follows:

1. above a height of 125 feet above curb level or 85 feet on a narrow street beyond 100 feet from any street line opposite a public park or from the intersection of such narrow street, a setback pursuant to the provisions of Section 23-433 (Standard setback regulations) shall apply;
2. the maximum building height provisions of a C6-3A District shall apply to zoning lots subject to the provisions of paragraph (a) of Section 118-21 (Floor Area Regulations); 
3. the maximum building height provisions of a C6-4A District shall apply to zoning lots subject to the provisions of paragraph (b) of Section 118-21; and
4. permitted obstructions pursuant to Section 35-61 shall apply.