When such uses abut a lot in a residential district, any lot upon which there is a dwelling as a permitted use under this chapter, or a right-of-way that serves a residential district, the use shall be screened, along the entire length of the property boundary abutting the residential district, dwelling, or right-of-way by a solid wall or a substantial, sightly, solid fence, not less than eight feet in height, together with a 20 feet wide planting strip on the outside of such wall or fence, which shall be maintained in good condition. Screening requirements within this planting strip shall be as provided for in other sections of these regulations. For such uses proposed within existing developments that do not provide the width required above, alternate screening requirements may be approved by the Board of Adjustment, provided that planting strip meets the minimum screening requirements of the Code.