If special trench bedding material is required for a pipe installation, it should be clean, __________, granular material up to __________ in size.

• A. Well-graded; 1 in
• B. Poorly graded; 2 in
• C. Uniformly graded; 3 in
• D. Well-graded; 2 in

Answer: (A)

Selecting trench bedding material relies on using a clean, well-graded granular mix that can be compacted around the pipe to provide stable support. A well-graded mix includes a range of particle sizes that fit together, reducing voids and enabling good density under load. Limiting the largest particle size to 1 inch prevents large stones from creating high spots or gaps under the pipe, which can lead to movement or settlement. The term “clean” means the material is free of organic matter and contaminants that could degrade performance over time. Choosing a poorly graded or uniformly graded material, or using larger stones, would not compact as evenly and could compromise the pipe’s stability.