(a) When installed in a ditch, each transmission line and main must be installed so that the pipe fits the ditch so as to minimize stresses and protect the pipe coating from damage.
(b) When a ditch for a transmission line or main is backfilled, it must be backfilled in a manner that:
(1) provides firm support under the pipe; and
(2) prevents damage to the pipe or pipe coating from equipment or from the backfill material.