Can an avocado tree be planted like this? (greywater)

In the book "build an oasis with greywater" on p. 49 they show a picture of an avocado tree which is planted on a mound 18-30" (46 - 75 cm) around this is a basin formed out were the grey water goes in. Is the mound high enough? My soil underneath is not very permeable so I should do something to allow drainage.
How fast should the water be able tp drain away?
The avocado I bought is a grafted one (Bacon) how close could you plant it to the house without damaging the foundation? The closer to the house the more protected it would be.