I don't know the exact specs, or requirements but I have built retaining walls, the biggest being in my brothers backyard on the lake. It measures 7 ft by about 60 ft long. What we did was as we built it, we started backfilling it, starting with about 8" of gravel behind the wall, all the way across and up to about 2 ft from the top, behing the gravel we put a silt screen to keep the dirt from filling in the gravel, then dirt. At the bottom of the wall about 6" above the ground we put PVC pipes in the morter joints through to the gravel for the weepholes, We also left a few small holes in the grout here and there for extra weepholes(probably not nesasary, but we overkill rather than underkill), they work great, but he is out of city limits, you will want to investigate this further, just to give an idea of how it is done. If you look close at this picture, http://www.homestead.com/foscue/files/adwalla.JPG , you can see where the gravel and silt screen is.
About the wall: This wall was built from the busted up concrete they used for a temporary slab to form and pour the concrete walls for a new Targets, it was a temporary slab so therefor had no steel or wire in it(for easy bustup and removal), it looks great and it was free! They were more than glad to load it on our dump trailor for us, just to get rid of it. We still have tons of it, literally. This wall was nesasary to stop the natural erosion.
If anyone would like to see the house and wall being built step by step, every phase, email me at email@example.com and I will send the link, I would rather not post it.