This past weekend was a mini-reunion for my partner's family at his mother's house. His two brothers from out of town visited, and his other brother that lives locally also dropped by. Unlike my family get-togethers, it was a nice visit. Nobody cried, no death threats were made, no fights broke out... It was kinda weird to me.
During the visit the subject of our geothermal adventure came up. Myron's youngest brother David was a geology major so I told him we were planning on covering over the mud with topsoil and just forgetting about it. I described it, showed him the pictures, and he confidently said it was Cooper marl. He went on to discuss how will set up like concrete and will not decompose. He related a report he had read of some work done where Cooper marl was extracted nearly 30 years ago and left exposed, and you can still see shoe prints and shovel indentations.
I did some research on my own last night and found a geologic survey that said Cooper marl is an effective replacement for concrete in setting building footings and pilings. In other words, this isn't plain old mud, so now it looks like I'll be hauling it off to the dump. Through the magic of Google I calculated that we have approximately 132 cubic feet of this stuff, and also calculated that my truck holds 40 cubic feet, so it looks like this is going to take a while.