I finished demolition in my basement in preparation for spray foaming the rim joists and walls.
I found a 30" hatch between the oil tank and what was left of the original coal storage bin. The hatch opened up into a 24" deep chamber with reinforced concrete ceiling and ran about 15' under my basement slab to where the coal furnace used to sit. There is a similar sized circular indentation in the concrete floor about where this tunnel ends, it looks like part of the tunnel was filled in with concrete to install the new oil furnace.
I found it on Saturday and was a little too scared to look into it until Sunday. It was much cleaner than I feared (no bones).
DW thought is was a good sign that my biggest fear was subhuman partially decomposed zombies slithering out of the hatch, as opposed to rats.
I tried to attach pictures.
