Drainage tile should be installed after grade is set and before soil has been conditioned. Which option describes the timing?

• A. Before grading is complete and after the soil has been conditioned
• B. After grade has been set and before soil has been conditioned
• C. While grading is being done
• D. While surface soil is being conditioned

Answer: (B)

The timing focuses on sequencing drainage work with the finished surface and soil preparation. You want to place drainage tile after the final grade is established so you know the exact outlet elevation and the slope of the tile path. Installing it before any soil conditioning keeps the trench walls and backfill in a stable state, so the tile can be bedded and backfilled cleanly without disturbed or overly compacted soil that could deform the trench or alter the slope. If you wait until after the soil has been conditioned, the soil can become more resistant or wet and may slump or compact differently around the tile, risking improper drainage or voids. So the best timing is after grade is set and before soil has been conditioned.