When can the minimum backfilled cover for buried piping be reduced to 18 inches?

The minimum backfilled cover for buried piping can be reduced to 18 inches when physical damage is otherwise prevented. This scenario acknowledges that the primary purpose of backfill is to protect the piping from external forces and potential damage. If adequate measures are in place to safeguard the pipeline from physical damage—such as placing the pipeline in a designated area where heavy equipment and vehicles are prohibited, or using protective barriers—there may be a justification for a reduced cover depth.

In contexts where physical damage can be reliably managed, regulatory standards may allow for less cover to accommodate construction or layout requirements without compromising the safety and integrity of the pipeline. This is particularly pertinent in settings where soil conditions, load requirements, or utility placements necessitate adjustments to standard practices.

The other options do not directly address the issue of protecting the piping from physical damage in a way that justifies a reduction in cover. Thus, the emphasis on preventing physical damage provides a robust reasoning for allowing a lesser depth of backfill in specific circumstances.