No, I computed a burial location some miles outside (and still on the way to Medina). This burial site (not far, at all, from TX-16) was where, it seems, the 1 bag of concrete was used. So, the visit to Medina (after the burial) was, seemingly, just to get rid of the evidence of the burial, according to my theory of this alleged crime.
In other words, I'm guessing he may have used an Apache Disposal dumpster in Medina, Texas, during that 13 mins in that area, to dispose of things like: the empty Quikrete bag, the empty water jug, and the empty, used, 5-gallon Home Depot bucket (with concrete residual still on it). Sadly, depending on how he performed the burial (especially whether the space for the body was large enough), then he also may (or may not) have disposed of the now-empty blue tarp in Medina. Obviously, you'd think he would avoid unrolling that tarp, if possible. On the other hand, he must have been very determined to finish the job, so I suppose, if the body wouldn't fit, then he may have considered all options, however gruesome.