Which statement describes the effect of compaction on permeability?

• A. Permeability increases
• B. Permeability decreases
• C. Permeability stays the same
• D. Permeability fluctuates

Answer: (B)

Compaction packs soil grains tighter, shrinking the void spaces and making the pores less connected. Permeability is about how easily water can move through those pores, so when the pore space becomes smaller and more tortuous, flow is hindered. As a result, the ease of flow, or permeability, decreases with compaction. The other possibilities don’t fit because compacted soil doesn’t create more or equally connected flow paths, and permeability doesn’t stay the same or fluctuate due to compaction alone.