The dump station (just a dump, no water for flushing out tanks) is on the outer edge of their parking lot when you first pull in, across from the convenience store and gas pumps. It's on the passenger side when you drive in, so you may have to circle around the gas pumps and come back at it. It's free to dump for anyone.

A water fill spigot is on the opposite of the building, next to the air machine.

Plenty of room for big rigs to pull in and out; we went in and bought a couple drinks and some food as a thank you since we didn't need gas.