The director may require such engineering or grade drawings, calculations, or computations as necessary to evaluate and insure proper drainage. The applicant must maintain the flow line of all drainage structures during excavation, or must provide adequate substitutes for such drainage structure as may be removed or blocked by the excavation. Should the flow line of a drainage structure be interrupted or diverted as a result of the excavation, the proper flow line shall be resorted by the applicant subsequent to the excavation. (Ord. 1583-98 § 3(part), 1998).