The drainage performance (drainage protection mat) of the system is more than 0.6/sec/cm.

(Test condition) ： pressure from upper 2kPa, hydraulic gradient 0.2)

The water permeability coefficients of the drainage protection mat is more than 0 .1cm/sec. For instance, even if it rains for 100mm/hour, it is entirely drained with 47cm section of the drainage mat.