The ridge of earth you are referring to is the end of the high fill of the railroad grade coming from the Cow Creek trestle. Close to the tank site there has been some earth moved by the State Park, so the grade is no longer intact. Park management thinks that the Railroad grade/fill is an impediment to new projects that are under consideration, so part of the grade may be bulldozed away in the future. BTW I was told that park property extends 30 feet beyond the north end of the Cow Creek bridge. While Dave Peterson's Google link shows the area very well, here is a marked up "hard copy" of the Google view.