In S Slope Districts, the following regulations shall apply.
A. 
No building, structure or land shall be used and no building or structure shall be hereafter erected, structurally altered or enlarged, except for the following uses:
(1) 
Reservation.
(2) 
Forestation.
(3) 
Recreation.
(4) 
Accessory use and building, customarily incident to any of the above uses, on the same lot and not involving the conduct of a business.
B. 
The following uses are permitted only as a conditional use requiring approval of the Zoning Hearing Board:
(1) 
Water tank, flagpole or open structure necessary to the proper functioning of and appurtenant to the above uses.
(2) 
Radio-television transmission or receiving tower and facilities.
On each lot not occupied by a building or structure and on each lot upon which a building is hereafter erected, enlarged or repaired, there shall be provided and maintained a lot area, yards and other open spaces which shall be not less than prescribed as follows.
A. 
Front yard depth: not less than 20 feet.
B. 
Side yard widths.
(1) 
Interior lot: not less than three feet on each side of the main building.
(2) 
Corner lot: not less than 20 feet on all yards abutting on a street or alley.
(3) 
Rear yard depth: not less than 20 feet. (Exclusive of any portion of depth to be used for permitted accessory uses or buildings.)