Thanks, Al. Those trenches remain a mystery. I was poking around the area a few weeks ago and I noticed that it is only the dunes/islands near the 1808 road that have them, so my best guess is that they were borrowing sand in order to build up the road through the swamp.
Possiblity I never thought of there.I noticed they were only on the south sides of those dune/islands though.This made me think possible trenches dug by Batsto workers to fight off a British attack that never came? From what I"ve read an attack was planned but the colonists spread the alarm and hence a battle was fought at Chestnut Neck instead of Batsto at least Thats the way I remember it which may be a flawed memory.Even at the end of a couple islands some of the trenches had the shape of redoubts built to protect cannon.The trenches do seem a little on the small side for defensive works but if they had dug much deeper they would have flooded and I"m sure theirs been some caving in.I also hit the islands further off the road and as you say there are no trenches out there.