You are looking for a "not so hidden" bison tube. Not far off the trail, easy park and grab with street parking nearby on the cul de sac. Bring your own pencil and remember to watch out for the usual cacti, prairie critters and critter holes!
"This cache has been placed for the CARMH 7 event.This cache should not be located prior to 7pm, Friday, August 19th. The caches for the CARMH 7 event are released early so that the geocaching community has an opportunity to plan their routes prior to the event start"