In the event that the building construction operation is arrested prior to completion of the building and the building permit thereof is allowed to expire, the premises shall be cleared of any rubbish, building materials or other unsightly accumulations, and any excavation for a building, basement, foundation, utility or otherwise, of a depth greater than two feet below finished grade, shall be filled and the topsoil replaced, or all such excavations shall be entirely surrounded by a substantial fence, at least six feet high, with necessary gates and locks that will effectively block access to the area. Such clearing, filling and/or fencing shall be completed not later than the expiration date of the building permit.