Section 28-102.5. Grading of lots

The regulation of lots, in conformity with
  the street on which they are  situated,  shall  be  calculated  at  curb
  level. Where a lot has more than one street frontage, and is so situated
  that  the  street  frontages  intersect,  the curb of the longest street
  frontage shall be used. When the street frontages do not intersect,  the
  curb  along each frontage shall be used to one-half the depth of the lot
  between street frontages. A lot as referred to in this section  28-102.5
  shall  mean  a  parcel  of land twenty-five feet by one hundred feet, or
  less, in one ownership whether adjacent land be in  the  same  or  other
  ownership;  but,  for this purpose, no land in the same ownership may be
  divided into lots smaller than twenty-five feet by one hundred feet.