Rationale

When placing dumped or poured backfill such as washed #57 and #67 stone, or CLSMs around pipe, the minimum trench widths are allowed to be reduced based on engineering review as outlined in Section 6.3. In my experience, public and private entities are hesitant to deviate from a minimum of 8” on either side of the pipe standard, even with engineering guidance. To help with this issue, I would like to review other industry standards (harmonizing where possible) and come up with additional language and illustrations for when backfill not requiring compaction or requiring minimal compaction is used around thermoplastic pipe.