In all zoning districts, the minimum lot area for any lot not serviced by an off-site sewerage system shall be 35,000 square feet. Nothing herein shall be construed, however, as preventing use of the lot sizes set forth for the respective zoning districts for a lot or lots which are presently unsewered but will be serviced by an off-site sewerage system as part of the approval of an Application for Development. Nothing herein shall also be construed as preventing variance relief, in appropriate circumstances, for lots which are unsewered but which are considered as isolated undersized lots.