Commencement of construction. Nothing herein contained shall require any change in laws or construction of a lawful use where building permits had been issued before September 1, 1988, and which were completed by March 1, 1989, or such further time as may have been allowed by the Township for large construction projects. However if no substantial construction has been made and no contract or contracts have been let prior to September 1, 1988, then the building permits affected are hereby declared void.