Uses which are permitted on either portion of a lot, which lot is divided by a zone boundary line, or which is coterminous with a zone boundary line, may be permitted to extend to the boundary line of such zone in which such use is permitted. Before a permit for such a use may be granted, however, the board of adjustment must find that the comprehensive plan of zoning will be maintained and that harmonious mixing of uses will be achieved thereby. (Ord. 6-18-81A, 6-18-1981)