I put this on gardening but thought people here might know more.

I have a septic tank in the back garden ( its a large back garden. Its
currently covered with grass but the stretch where the tank is is long and
flatish ( slight slope to the right) and did have apple trees on it once nut
those died several years ago. I was wondering if it was OK to dig up this
section of land and put a garden in ? Would I be likely to disturb anything
important ( like drains) by digging round and down from the septic tank for
a garden bed about 100 ft long and 20 feet wide?