Ceremonial Spring - visible from the road in Concord, MA

I drove by this driveway for years before noticing rock piles but, eventually noticed at least one. Then FFC mentioned wanting to show me some rock piles "visible from the road" and it turned out he knew the people. So last weekend we drove over there and got a good look around. At first I thought these were just "bottom of the yard" piles. For example this one has been recently disturbed.But there were too many of the piles and they were situated, properly, around a spring facing the west. There is a rough boulder alignment in there that is due east-west (an "equinox alignment"). I was surprised by how many piles were in there, not visible from the road. Perhaps 10-15 separate piles? Some of them seemed a bit effigy-like, having a bit of symmetry. Also there were split-filled and split-wedged rocks: These are all common features at a spring: effigy-like piles, split-wedged rocks, rough alignments. Here is FFC in his element: