You don't want to plant anything except grass over a septic field. Sun needs to get at it--at least that's what the very experienced guy who puts in septic tanks told me.

Septic tanks, septic pipes/vents and septic leach fields are all different components of a septic system. Septic leach fields are best left to turf grasses or groundcovers but perennials or small shrubs in proximity to vents or tanks are perfectly fine. Just avoid any trees :-)

FWIW, there are many different types of septic systems, some of which have different processes so not practical to offer blanket advice. Also, most shrubs will have surface oriented roots, if that helps.

@laceyvail 6A, WV @gardengal48. It's not a septic system. We have public sewer. This is a clean out access