Here is an update on the Rock River scene: the riverbed is painted; work is progressing with the abutments and pier color and weathering; the final trusses are being assembled; and foam landforms are starting to take shape.

Below are some images with captions…

Here is one of the prototype abutments. My goal is to mimic the general feel of the concrete structures and not try and reproduce their look exactly.
After the initial coloring, I went back and added additional PanPastel coloring, sealed each layer, and added a final non-sealed pastel layer (see image below).
Once I glued the abutments in place I added distressed ties, ballast, and also attached a tin registration plate. Magnets were then glued in precise position on the two girder spans. I took this approach so that I could remove both spans, if necessary, and then reposition them exactly as originally set up.
Finally, I needed larger bridge shoes which will eventually be placed once the trusses are attached. I found a shoe design at Thingiverse, modified it using Tinkercad, and sent the final .stl file to my friend Michael P. who 3D printed the shoes. Worked great! You can see a comparison in the photo between the original Micro Engineering cast shoe and the larger 3D printed shoes.