Curb grade and elevation shall be four inches (4") lower than official grade for sidewalk areas sixteen feet (16') wide, and shall be three inches (3") lower than official grade for sidewalk areas twelve feet (12') wide. Sidewalk areas other than the above shall slope downward from the official grade at the property line at the rate of one-fourth inch (1/4") vertically for each foot of horizontal distance. (Ord. 73, 6-17-1940)