In any district other than a residential district, any use which is nonconforming because it is not located within a building fully enclosed on all sides may be continued for three (3) years after the effective date of the Comprehensive Development Regulations, provided that after the expiration of that period such nonconforming use shall be terminated. Any other provision to the contrary notwithstanding, however, no such use will be required to terminate if, within the said period, such use shall be located within a completely enclosed building complying with the requirements of the district in which it is located, or, if within the said period, such use shall be surrounded with a solid fence or material and design acceptable to the Planning Board, which fence shall be one (1) foot higher than any material stored outdoors, provided that such fence shall be maintained in good condition at all times.