Whenever, in the opinion of the Planning Commission, the land involved in any subdivision is of such size or shape, or is subject to such title limitations of record, or is affected by such topographical location or conditions, or is to be devoted to such use that it is impossible or impracticable in the particular case for the subdivider to conform fully to the regulations contained in this chapter, the Planning Commission may make such modifications thereof as, in its opinion, are reasonably necessary or expedient and in conformity with the State Subdivision Map Act. In the case of subdivisions of four or less units, this determination may be made by the Planning Director with the concurrence of the City Engineer.
('61 Code, § 10-2.105)