17.10    Backfill of Excavations

Backfill containing large rock, paving material, cinders, large  or sharply angular substance, or corrosive material, shall not be placed in an excavation where such material may damage ducts, cables, or other substructures  or prevent adequate compaction of the fill or contribute to corrosion of the ducts, cables or other substructures (See Appendix B, Figs. 5, 6 and 7.) .