The size, slope, alignment and materials of construction of a building sewer, and the methods to be used in excavating, placing of the pipe, jointing, testing and backfilling the trench shall all conform to the requirements of the building and plumbing code or other applicable rules and regulations of the city. In the absence of code provisions or in amplification thereof, the materials and procedures set forth in appropriate specifications of the ASTM and WPCF Manual of Practice No. 9 shall apply. All excavations required for the installation of a building sewer shall be open trench work unless otherwise approved by the superintendent, and no backfilling shall be done until the installation is approved by the superintendent. (Ord. 255, Sec. 2)