Whenever it is necessary to break through existing pavement for the purpose of construction, repairing, restoring, maintaining, or inspecting underground utilities or other services, and where the trench therefor is four feet or more in depth, the pavement and the base shall be removed to at least six inches beyond the outer limits of the subgrade that is to be distributed in order to prevent settlement, and a six-inch shoulder of undisturbed material (earth) shall be provided on each side of the excavated trench. The face of the remaining pavement shall be approximately vertical. A power-driven concrete saw shall be used to cut a kerf sufficient to permit complete breakage of the pavement or base without ragged edges, and no other method shall be followed in breaking through the pavement, except asphalt pavement shall be scored or otherwise cut. No pile driver shall be used in breaking up the pavement. No backfill of undermined paving shall be permitted or done. (Ord. A-409 §1, 1960).