Where review by the full Board is required or deemed appropriate, in addition to meeting within the time period provided in § 196-36.1F, the Design Review Board shall make its determination on the application within 15 days after such meeting or, if the Design Review Board shall require additional documents for its review, within 15 days after the submission has been completed, unless such time is extended in either case by the applicant. If such time expires without such extension, and without a determination by the Design Review Board, design approval shall be deemed to have been granted.