You don't mention where you are in Calif. but I have had several homes on
San Diego and San Diego Co. and any wall 3 ft or taller requires a building
permit..

Normally I wouldn't even mention this since I do a lot without a permit..
However I do know there is a reason for a permit and proper building plans
and inspection of division and retaining walls..

A improperly built wall can be very dangerous.. I happen to know of some
children who were crushed when a wall collapsed on to them.. All they were
doing was, a kid thing, swinging on a gate..

Your masonary retaining wall requires better planning and engineering than
you are going to find in a news group..

Sorry

Steve