Building a culvert

I have several inches between the front of the layout and the track which I want to fill with interesting scenery. One scene I wanted to model was a culvert running under the tracks. This would allow me to model water, perhaps a shallow stream, and it would give the illusion that the railroad had proper civil engineering and drainage. 

Since I had a maximum height of 2" of foam to work with, my culvert had to be small. Though there are some commercial castings available, and likely even more through 3D modeling websites, I decided to make one myself out of styrene because it looked like a fun project. I drew up a sketch on graph paper based on an HO scale casting from Woodland Scenics. Once I settled on a hole size of 3/4", everything fell into place. You can see from the date on the drawing that I started it awhile ago, and then put it on hold.

I used some scraps of 0.060" thick styrene to build the main wall and two wing walls. Then, I drilled the hole out on my drill press. I was fortunate that I had a 3/4" forstner bit lying around from building benchwork and it made quick work. The graph paper was used to align the wing walls to the main wall, first tacking them with small dabs of super glue gel along the joints to hold them temporarily and then later by applying MEK.

I then built up a "log cabin" series of interconnected braces on the back along the joints to further secure them. Next, some 1/4" square styrene was glued along all five edges (everything but the bottom). They were left oversize and grossly extended beyond the edges in places. I let everything cure overnight.

The next day I used a razor saw to cut along the edges, leaving nice clean lines. Then, I took some filler putty and applied it to some of the joints. I wanted to create the illusion of casting marks from when the concrete was poured into wooden molds so I used a toothpick to randomly apply putty to various areas, and then slid the toothpick in horizontal motions to impart striation lines. Everything was again left to cure.

I sprayed everything with flat gray paint. I followed this up with various black ink and alcohol washes to look like old, weathered concrete. I wasn't happy with it because it was too dark so I then added drybrushing of light gray horizontally to the faces. This was followed up with a lighter brown oil wash.

I needed a pipe to go on the backside to extend out at least an inch or two to create the illusion that the culvert did lead back somewhere. It had to be around 3/4" inside diameter, which matched the hole, and it hopefully would be cheap. I looked at metal and PVC but couldn't find anything suitable and/or cheap. 

I mentioned my dilemma at the local hardware store and they invited me into the back room where lots of broken things were being stored as a result of a recent remodeling. They had a metal telescoping mop handle that was broken but one of the pieces was exactly the right diameter and the price... free.. was perfect. I brought it home and cut it up on my bandsaw. Then, a piece was sprayed with gray primer inside and out and it was glued to the back.

Something still wasn't right. It looked too new. So I used a blade to chip around the edges and add some cracks. 

Then I sprayed it with Rustoleum Camouflage tan paint and that did it. All that was necessary was some light drybrushing with tan paint and it was done. 

Now it just needs to be installed on the layout.