A. From Foreign Substructures (Except Supply Systems)Rule 41.4-A1 (1) Independently Installed: Ducts carrying communication cables and conductors for public use, when independently installed, shall be separated where practicable from gas, water, oil, or other pipe systems, by a clearance of at least 12 inches when paralleling and by at least 6 inches when crossing. (2) Concurrently Installed: Duct