What is the most important purpose that backfill serves in a trench for a water line?

• A. distribute surface loads
• B. neutralize chemicals
• C. prevent infiltration
• D. insulate the pipe

Answer: (A)

Distributing surface loads is the main job of backfill. When a trench is buried, the weight of vehicles, soil, and other surface loads can press down on the pipe. Properly compacted backfill forms a solid mass that spreads those loads around and over the pipe rather than concentrating them at a single point. This helps prevent crushing, deflection, and settlement that could damage the pipe or joints over time.

The other purposes listed aren’t the primary function of backfill: preventing infiltration is more about joints and sealing, insulation is a minor benefit, and neutralizing chemicals isn’t a role of backfill.