Kittanning Run is one of two small streams to pass beneath Horseshoe Curve, the other being Glenwhite Run. Kittanning passes under the northern half of the curve through a stone culvert. The Woodland Scenic stone culvert isn't an exact match, but it's a close enough stand in. I painted it Tamiya "Red Brown" and hit it with a coat of weather wash.
For installation, I cut out a portion of the hillside, glued the culvert in with some foam tack glue and filled in around it with some flex paste. Rather than cut an actual tunnel under the four tracks as I did with the Scotch Run bridge, this time I affixed a piece of black foam core board to the back of the culvert. Is far enough away from the edge of the layout that it isn't really noticeable.
I also decided to go ahead and weather this BLMA gondola.