Jim Dufour asked about seeing the details of how I was installing this culvert, so here you go! Note that there is some fancy foam cutting around it, but foam is really very easy to work with as you'll see coming up here. The area in front of the vertical smooth foam block supporting the culvert apron will have a "tumble" of rocks in front of it. I'm modeling this in mid-summer, with just a trickle of water and no flow that I need to be concerned with. This is a culvert emptying into the river below.