No final certificate of occupancy or certificate of compliance shall be issued until all improvements shown on the final site plan as approved by the Planning Board, reasonably necessary to the proper and safe operation and occupancy of any completed facilities, are installed or until a sufficient performance guarantee, such as a letter of credit, has been provided to the Town for improvements not yet completed. The need for, and sufficiency of, such performance guarantee shall be determined by the Town Engineer after consultation with the Building Inspector or other persons designated by the Planning Board. The Planning Board may waive the requirement for such performance guarantee if, in its discretion, it determines that the guarantee is not needed.