Got to second the confined spaces concerns! Do you know a utilities type person that can bring you a genny and air blower to ventilate the space and loan you a 4 head gas detection unit? You should also ensure your top man DOES NOT go in to assist if you are in trouble, they are there to get help, not add to the casualties!
Leading cause of fatalities is lack of oxygen, decomposition of organic material or rusting metal can cause this and you won’t have a clue until you pass out.
Once that is covered, I’d be eager to get in there!