To limit the probability of inadequate percolation down to drain tiles or pipes, which could lead to silting-up, which could lead to excessive moisture loading on foundation walls and basement floors.
This is to limit the probability of the accumulation of water under hydrostatic pressure, which could lead to:
This is to limit the probability of harm to persons.
To limit the probability of inadequate percolation down to drain tiles or pipes, which could lead to silting-up, which could lead to excessive moisture loading on the soil immediately beneath the footings, which could lead to saturation and a reduction in the soil's bearing capacity, which could lead to the failure of foundation walls and basement floors, which could lead to harm to persons.