The above are two good, and siilar in approach answers, but there are two issues it seems no one includes:
1) If you house was built before 1978 it must be inspected by a certified contractor or lead ... read more
In Georgia a wall retaining over 48" grade requires an engineers stamp.
You might consider terracing and have two or more lower retaining walls. Be aware of hydrostatic pressure and provide adequate w ... read more