I'm going to build a small retaining wall (about 3' tall) along the sidewalk in front of my house using Versa-lok standard blocks. They recommend compacted gravel base about 18" deep for blocks that are 12" deep. This would result in the gravel base a few inches in front and in back of the first course of blocks. Because of my sidewalk, I cannot excavate in front of the wall to have the gravel base in front of the wall. How big of a problem would this pose for such a short wall? I'm also planning to use geogrid reinforcement fabric, proper drainage, etc.
Thanks in advance.