we have a place like "witches hollow" in iowa near where I hunt. There is a beaver dam there and there is always green grass and shrubs around it. Even after it snows it dries off quicker and looks out of place. There is a beaver there who is as big as a german shephard that walks upright. My brother swears he has seen it.
This does sound like te place I refered to.
It may have a higher concentration of minerals and also cave fed springs.
I dont know about the bipedal Beaver but entirely probable.