Along each side or rear property line which adjoins existing residences or a residence district, a buffer planting strip shall be provided, which shall not be less than 30 feet in width and on which shall be placed shrubbery, trees or other suitable plantings sufficient to constitute an effective visual and noise abating screen. Along each street line bounding the district, a twenty-foot line buffer strip shall be provided, suitably landscaped, except for necessary sidewalks and accessways. Nothing herein provided shall prohibit the erection of a suitable fence or wall on the required buffer areas. Buffers shall be 100% evergreen, planted six feet apart in two rows within a 10 foot width, and shall be six to eight feet high at time of initial planting. Such planting shall provide a thick, dense visual buffer from the ground to a height of eight feet.