I saw a snake who looked a lot like that
at this year's COC Long, on course 8, near control 9 (a refreshment control, no less).
I unknowingly stepped right over the snake as I ran in to the control, thought I saw movement under my feet, turned around, and sure enough there s/he was. We had a curious look at each other, then continued on our way. It was a neat encounter!
I assume the one I saw was a rat snake, as one of the COC info bulletins said they're common at Foley Mountain and harmless to humans. Definitely bigger than your typical garter snake!