It is the default in the demo scene. I just adjusted the Min/Max Volume values of the SurfaceEffects for FootstepsOnTile, FootstepsOnGrass, Dirt, Metal, Sand, Water and Wood. The volume on ORG-toe_R and ORG-toe_L would never change from the default 0.4.
After sniffing around in the AudioManager I noticed the volume value was not being passed all the way down to PlayInternal(...) and maybe PlayAtPositionInternal(...), I don't remember now. So I added it. A value passed < 0f will not adjust the volume at all.
Now it works great though it could be somewhat problematic as the AudioSource volume is always set to the last played SurfaceEffects volume. Requiring all subsequent audio to explicitly set the appropriate volume. In the case of the Footsteps I don't think that is a problem but, my lack of intimacy with UCC could get me in trouble.