A small rock pile site in Harvard MA

This is one of those inveitable little sites you see so frequently in the woods behind people's houses out here in Harvard and Bolton, that you wonder: do the people living there notice these rock piles? And if they do, do they have any idea how common these little sites are in the rest of the Town?

I went in the conservation land entrance and then hung a right off the trail, putting me behind people's houses as I went down the hill towards the wetter lowlands. I wanted to turn back because I didn't see anything and then, at the last moment I saw this on the other side of a stone wall:
And then I realized it was a small site of rock piles supported on the few boulders in there. There were not too many boulders but most (all?) were being used to support rock piles.
Note the rubber tires in the background.
At this point I was so paranoid about being in plain sight of the houses that I had to move on and not take many more pictures. A couple more similar piles.
Finally the site played out up the little valley I was following.

I do not know what this site is an example of and was not paying good attention to the landscape because of the paranoia; but this is a good example of one particular kind of site: all the piles have a common look, a common basic architecture. It is too bad I did not pay attention to the topography before high-tailing it out of there.