Which of the following is a common trench backfill requirement after pipe installation?

• A. Use of concrete encasement around the pipe
• B. Leaving backfill material loose to allow drainage
• C. Painting the backfill to match surroundings
• D. Proper compaction and placement of suitable backfill material to original grade.

Answer: (D)

After installing a pipe, the trench backfill needs to be placed and compacted to restore the ground to its original strength and grade. Proper backfill provides the bearing capacity the pipe and overlying loads require, prevents settlement that can stress joints or deform the trench, and helps maintain drainage away from the pipe. Place suitable material in lifts, using excavated soil if it meets quality standards or approved fill otherwise, and compact each lift until the desired density is reached. Bring the material up to the original grade and ensure the surface can carry loads and drain properly. Concrete encasement around the pipe is not a standard backfill requirement in typical installations, and leaving backfill loose creates voids and settlement risks, while painting backfill is not functional.