Expansion. A structure, the use of which does not conform to the use regulations for the district in which it is situated, may be extended; provided, however, that as to such extension, all of the requirements as to distance from highways and lot lines as provided by this chapter for such structure in the zone for which such nonconforming use would be a conforming use or in the zone in which such structure is located, whichever requirements are greater, must be complied with, and that the extent of such expansion, whether occurring as a single expansion or as the aggregate of two or more smaller expansions, does not exceed 50% of the gross floor area of the structure dedicated to the nonconforming use at the time of the enactment of this chapter, and that the nonconforming intensity of use will not be increased with respect to traffic usage, amount of effluent, noise, lights, odors, hours of operation, or other environmental impacts.