(a) Steep Slopes; Front Yard Garage. In any SR District or the VR District where the natural grade of a lot within the required front yard has an average slope, normal to the front lot line at every point along such line, of such a degree or percent of slope that it is not practicable to provide a driveway with a grade of twelve percent (12%) or less to a private garage conforming to the requirements of this Zoning Ordinance, such garage may be located within such front yard, but not in any case closer than twelve feet to the street right-of-way line.
(b) Side Yard Modifications; Corner Lot. For a side yard along the side street lot line of a corner lot, which lot abuts the rear, either directly or across the alley, the side lot line shall have a width equal to the required depth of the front yard on such other lot fronting the side street.
(c) Frontage Modifications. In the case of curvilinear streets and cul-de-sacs, the Board of Zoning and Building Appeals may authorize a reduction of the otherwise specified lot frontage in SR Districts, provided that:
(1) The lot width measured at the building line equals the frontage required in the district where located;
(2) The front lot line is not less than forty feet in any event; and
(3) Such reduction of frontage will not result in a reduction of the required lot area.