There are two grain facilities with loops in my neck of the woods that have been constructed within the last 20 years. The Double J Milling facility is in Mountain Home, ID. It was built to supply grain (mostly corn) to a large J R Simplot feedlot in Grand View, ID. I once had the opportunity to ride in the locomotive (it was a UP SD60M) while the corn was being unloaded. In order to avoid the issue with slack between cars, the train was backed up one car at a time to unload. In the photo it looks like there are about 13 covered hoppers left to unload.
The J.D. Heiskell & Co. facility is further east in Gooding, ID. I visited this facility shortly after it was built because my work required me to conduct a field examination/verification of their water rights. At the time it was owned by Land O' Lakes if I remember correctly.
I am hoping to figure out a way to model this one.