I had never seen anything like that in my life so I sent a pic to a friend who does excavation work and he asked me what it was,..... not a good sign.
I told him it was my leaching field distribution box and he asked me why it was so big...again, not the answer I wanted to hear.
I opted to try and see if it had a cover I could lift of and after a few minutes of work, I was surprised.
Within an hour, i had removed three of these D boxes and was surprised to see that there were no pipes going out to a leaching field, just these empty boxes surrounded by sand and pea stone. I later found out that these systems were used years ago in areas with a high water table, like living on the ocean.\