N.Y.C. Admin. Code § 28-305.4.2: § 28-305.4.2 Owner's responsibility.

Owners of retaining walls with a height of ten feet or more and fronting a public right-of-way shall comply with the requirements of this section. For the purposes of this section, the height of a retaining wall shall be the distance from the top of the ground in front of the wall to the top of the wall stem, or wall step for stepped walls, including any parapets or fencing capable of retaining material.