Each application for a permit shall state the length of time it is estimated will elapse from the commencement of the work until the restoration of the surface of the ground, or until the refill is made ready for the pavement to be put on by the city if the city restores such surface pavement. It shall be unlawful to fail to comply with this time limitation unless permission for an extension of time is granted by the building inspector. (Prior code § 33-3-10)