After any excavation is commenced, the work of making and backfilling the same shall be prosecuted with due diligence, and so as not to obstruct the street or other public place or travel thereon, more than is actually necessary therefor. If the work is not so prosecuted, or the work of backfilling does not, in the judgment of the public works director comply with the terms of this chapter, the public works director shall notify the person named in the permit required by this chapter, in writing, that the work is not being prosecuted with due diligence, or that the backfilling of such excavation has not been properly done, and shall require such person, within three days, after the service of such notice, to proceed with diligent prosecution of such work, or properly to complete the same as the case may be. Such notice shall be served personally, or by leaving the same at the residence or place of business of such person as shown in the application for the permit, or such notice may be served by depositing the same in the United States mail in a sealed envelope, postage fully prepaid for certified mail, addressed to such person at such place of business or his residence, if known, or if unknown, addressed to his last known address. If such notice is not complied with, the public works director may do or cause such work as may be necessary to backfill such excavation, and to restore the street or other public place, or part therefor excavated, to as good a condition as the same was in before such excavation was made. (Ord. 1970 NCS § 3 (part), 1994; Ord. 1369 NCS §2 (part), 1979.)