Boring will be required when it is feasible to tunnel underneath any portion of any street or sidewalk in the city which is paved with concrete or asphalt paving. The street or sidewalk paved with concrete and/or asphalt may be excavated as otherwise provided in this chapter, if road boring is not feasible as determined by the mayor, after taking into consideration the location, costs, and time involved; and where a proper permit has been secured, road bores may be driven, or drilled under any such pavement; provided, that upon completion of the work involved, the backfill shall be compacted with sand. (1985 Code ch. 19 § 3-10)