The Dreaded Septic bed

The Dreaded Septic bed

Hey guys, i have a quick question. I have a client who would like native materials planted around and over her bed, because they have already badly disturbed the forest to install it there. I am a city folk, so I don't know much about how a septic bed works. I am doing as they ask, which is do some research for them and test their soil, but when the septic bed is fully functional, won't the soil be very poor? Either way, I only want to recommend groundcovers for their bed, if any, though they have already been advised to only plant grass. What should I do? I want them to be happy with something, but with very shallow roots.
well, not my room…but my apartment.

well, not my room…but my apartment.

Garden update.

Garden update.

Plant ID please

Plant ID please

Basil sprouts

Basil sprouts

Just a couple pictures.

Just a couple pictures.

From my garden and terrace…

From my garden and terrace…