This is #5 in the park and grab Salt Dome series. These are storage facilities for the abrasives that MDOT places on our highways in the winter to help us get around, or help our cars rust out quicker, whichever way you want to look at it. Anyway, we look at as an excuse to place another geocache. This should be a nice quick cache to add to your collection. The Salt Dome is nearby at the truck stop where they also have a pretty good restaurant.
Congrats to journey374,jercad, and fastangrybird for "FTF".