Backfill height 18 inches? The trench backfilled in 6" layers to how many inches above the top crown?

• A. 12"
• B. 24"
• C. 18"
• D. 36"

Answer: (C)

Backfill around buried pipe is placed in six‑inch lifts to ensure proper compaction and support. To reach eighteen inches above the pipe crown, you would make three lifts: six inches plus six inches plus six inches equals eighteen inches. So after three successive lifts, the backfill sits eighteen inches above the crown. If you did fewer lifts, the height would be proportionally less (two lifts = twelve inches; four lifts = twenty-four inches).