The hydraulic conductivity of the covering material must not be less than what value?

• A. 0.001 m/day
• B. 0.01 m/day
• C. 0.1 m/day
• D. 1 m/day

Answer: (B)

A covering material needs to move water through it at a rate that prevents surface pooling while still protecting and directing water into the soil below. The value 0.01 m/day represents the minimum permeability that keeps the cover from being too retentive; if the cover were slower than this, rainfall would pond on the surface and hinder proper drainage to the absorption area.

So, the covering material must not be less than 0.01 m/day. Values like 0.001 m/day would be too slow, causing surface water problems, while higher values (0.1 or 1 m/day) simply indicate more permeable cover, which meets or exceeds the minimum requirement.