I just checked all my old photos of this place and I didn't see it in them...I'm not sure where it's supposed to be but I don't have pics of every room there either (most of the largest battery though) The next battery has two pieces (one more difficult to find than the other). I try to go out there at least once a year. I don't remember that door either, but it's been a while. I have yet to go in the winter though.
Don't remember that hole without the trash. My ex went partially down in one of the holes in the smaller battery and stuck a camera in a space that he couldn't fit in, and it appears to be a tunnel to

but also filled with trash and dirt. Not much to look at, not even in pics. The only place I can think of with welded shut doors is Wetherill.