Everyone is used to creating a subassembly with some sort of end condition that finds existing ground at a slope but have you ever tried the retaining wall subassemblies? If not you are in for a surprise and a little bit of frustration if you don't know what to look for.

First lets start with some of the challenges you might face with some of these subasseblies. I used the RetainWallTapered subassembly for this example. This particular subassembly was challenging because I could create a corridor with it but creating a finished ground surface wasn't showing up the way the corridor was designed. The surface wouldn't meet existing ground. When the roadway was in a fill condtion, the surface would stop at the top of the wall and not create the surface back down to existing ground. My interpretation of this subassembly is that it should search for existing ground no matter if it is in a cut or fill situation.
So the question you may be asking yourself is, how do I make this work? Well, that is where IMAGINiT comes in. We were able to find a fairly simply solution. Create your assembly as you normally would, placing subassemblies onto the assembly using the desired left and right settings and desired dimensions. Once your assembly is complete, create a corridor using this assembly and be sure to set the surface targets to find existing ground. Civil 3D creates the corridor and surface. Part of the corridor is the features lines from each subassembly. We will be looking for the P14 point code which should create the RW_Hinge feature line. You may need to rotate the screen into a 3D view to be able to find this particular feature line. Once you have found it we are going to create a grading feature line form a corridor. I suggest you name this feature line something that makes sense to you and we want to be sure to leave the dynamic link checkbox checked. Once this feature line is created use the grading tools to create grading at a distance. Use a distance of 0.01 and a grade of 0.1%, this will give the retaining wall a slight slope (which I believe is the problem with this subassembly from the beginning. There is not slope to the wall so it creates a vertical face. Add this feature to the proposed surface created from the corridor and that should solve the problem. There are also a couple of tips and tricks to creating the surface you might try. The first is to be sure an turn on overhang correction and the other is to add feature lines from the retaining wall to the surface in addition to following the top links. The feature linew would be the top of the wall and where the feature line is to meet the surface (RW_Hinge). Your surface should now meet the existing ground.
Special thanks to Mick Reynolds for his help with this post.