In addition to any certification pursuant to Section 91-83 (Retail Uses Within Existing Arcades), inclusive, or an authorization pursuant to Section 91-841 (Authorization for retail uses within existing arcades), the City Planning Commission may permit a horizontal enlargement of 7,500 square feet or greater within Areas A or B on Map 9 in Appendix A of this Chapter, provided that the Commission finds that the public amenity or improvement that is provided on the zoning lot is of equal or greater benefit to the public than the arcade to be eliminated or reduced.

For the purposes of calculating the total area of the horizontal enlargement that is subject to the special permit, the aggregate area of the horizontal enlargement permitted by any prior certification pursuant to Section 91-83, inclusive, and prior authorizations pursuant to Section 91-841 shall be included in such calculation, except the area of an indoor public space provided in accordance with the provision of Section 91-834 (Indoor public spaces) shall be excluded from such calculation.

As part of the special permit, the Commission may modify the requirements of Section 91-831 (Ground floor requirements), the provisions of Sections 91-832 (Plaza improvements) and 91-833 (Special regulations for plazas less than 40 feet in depth) for publicly accessible open areas and the provisions of Section 91-834 for indoor public spaces. In no event shall an enlargement be permitted within a publicly accessible open area or other required open area unless specified on Map 9 in Appendix A of this Chapter.

The Commission may prescribe additional conditions and safeguards to enhance the relationship between the enlargement and the surrounding streets, buildings and public open areas.