Failure to do so within said period shall be deemed to be a grant of tentative approval of the development plan as submitted. In the event, however, that tentative approval is granted subject to conditions, the applicant may, within 30 days after receiving a copy of the official written communication from the Board of Commissioners, notify the Board of Commissioners of his refusal to accept all said conditions, in which case, the Board of Commissioners shall be deemed to have denied tentative approval of the development plan. In the event the applicant does not, within said period, notify the Board of Commissioners of his refusal to accept all said conditions, tentative approval of the development plan, with all said conditions, shall stand as granted.