Under stable bottom conditions, the trench bottom must be bedded and initially backfilled to comply with which of the following?

• A. The grade only.
• B. Bedding depth only.
• C. All the following requirements.
• D. No backfill required.

Answer: (C)

The key idea is that a pipe laid in a trench must have both a proper bearing surface and protective support, even when the trench bottom is stable. Bedding creates a uniform, continuous support under the pipe so the invert elevation and grade are maintained and the pipe isn’t subject to rocking or point loads. Initial backfill then surrounds the pipe with material and is compacted to the required depth to hold the pipe in place during the rest of the backfilling and to prevent movement or settlement. Because both correct bed depth and appropriate initial backfill are required to meet the installation specs, compliance with all of these requirements is necessary. Skipping backfill or addressing only one aspect would jeopardize the pipe’s alignment, strength, and long-term performance.