Traversing Grassy Pond Conservation Land - Acton, MA

I took a couple walks last month, both in Acton, going through woods and bits of people's backyards for an entire walk of 2-3 hours, without being seen. It is astounding that I was able to spend that long walking through undisturbed woods, in a neighboring town where I have been walking for years. It is not at all astounding to find several new rock pile sites. Of course that is to be expected in Acton.

I did not cross any roads. I parked at 'A' and a few yards into the woods there was a little rock stack, possibly modern, and a split filled rock.

Then northward, skirting houses and though a notch, then downhill to a little vernal pond somewhere around 'B'. The Acton trail map (critiqued for its weird compass orientation and lack of useful detail - see here) shows a vernal pond but, at this point, I am still off that map to the left (southeast!).
At the vernal pond:

You get the idea. Four or five piles hiding in the ferns.

Then I strayed as far to the left as I could (so actually west) down to the edge of the wet places. And around 'C' [I think] I was really in someone's back yards, pinched between the open space of the house and the swamp to my right, when I found two piles right at the edge of the water. One turned out to have a "tail" and a lump of white rock. The other was just a simple pile. Perhaps it once had vertical sides. This is one of the more interesting thing I have seen in a while - Acton or not.
First pile:

 closer:

Second pile:

Back of 1st pile:

 closer:

View back towards pile from the side:

Back of the second pile:

And that was the end of the excitement. From there ('C') I squeaked between houses to left and right, walked for a while without seeing anything notable and finally came to a small site, right on the yellow trail, about at 'D'. It was right at the start of the water, which flows south from there:

To the upper left in the picture!  

I exited the woods, just below the word "ROAD" on topo map above. 

Update:  Curt H. wanted to know more about the piles at 'D'. Here are a couple of pictures:

 

Here we are looking across the "yellow" trail.