Finally got the whole top part of it dug up. I'm puzzled. It looks a lot longer than that in the video/pics, but I guess the length is deceiving just like the height. My previous method of measuring it was by sticking an old fence post in (had to bend it to get through the small opening) and going back to the wall, then marking the post and measuring it when I pulled it out. I think it went diagonal and probably threw off the numbers, however. The width was easily measured from wall to wall. The depth still seems to be about 4.5 feet on average. So, it is probably more like 7 feet long. I'll get some official measurements later today. This will change how much dirt I need to get delivered, of course.
I'm still confused about the random space that I initially dug out with the tin over it. I thought it was the lid moved out of place, like you initially suggested. However, I'm not seeing any lid humped up over the concrete roof of it. I have also uncovered the first - and so far only - lid. It is flush and where it needs to be. There's also a crack on the other side of the lid. Unless there's another one hiding under the little bit of dirt there further on the side away from the house, I'm not sure that there is another lid. That will make things very interesting. I poked around and the middle feels like a solid slab about 3 feet long. So here's hoping that the end has a lid hidden somewhere. I found the pipe on the back, but haven't gone down far enough to view it yet and just make sure that it is capped.
The lid didn't seem to be cemented on. I dug the dirt away from the sides of it and in the morning I should be able to lift it up one side at a time and move it over onto the roof slab next to it temporarily to get better video and when I go to fill it in. I'd like to particularly get better pics and video of the side close to the house to examine in detail and see if I see any cracks in the walls, etc. I won't be going down there to fix any that are seen, but simply to know. I'm sure that even after all of these years, it is likely very nasty and bacteria-ridden down there.
When they make the dirt drop and fill the hole, I may ask them to push the dirt that I have dug out back over on top of it so that I don't have to spend any more time on it. What would take me two hours will probably take them all of 5 minutes or less. I'll call them Monday to get a quote on the Bobcat work. It says they deliver in tandem and half tandem loads. I sure hope they can make it less than the 7 cubic yards (apparently about half of a dump truck, or 14 cubic yards on average for a full truck). Current guesstimates are 7 feet long, 4.5 feet deep (just to make sure I have enough) and 4 feet wide. If my math is right, that would only be about 4.7 cubic yards of fill dirt. But I want to make sure I get that right so that I don't end up with way more than I need. I sure hope I can find another lid. The one that I dug up is just teetering on the edges. The rocks are coming out of the concrete as I dig and scrape it a little bit. I see a lot of areas where the concrete is corroding to the point where chunks come out of the slabs while digging, so I'm quite glad to have discovered this. While it seems "solid"...not sure how much longer that concrete would hold under the weight of the dirt. Looks very poorly made. Man, they must have taken every shortcut they could have when they built these houses in this neighborhood.