Lifecycle of an open pit mine

They are building a condo in the vacant lot across the street. It’s been going on for awhile. Initially the lot was mostly flat, with an open pit mine to the right. It looked like it had been the victim of a snatch and grab of a lot of dirt.
About two months ago some diggers and trucks made a determined effort to dig a nice rectangular hole on the left. They made good progress, leaving a professional looking void. Then a month ago, all work stopped. No one showed up. No dirt moved. The earth moving machines rusted in their own graveyard.
Last week it started up again and things got weird. They filled in the open pit mine with some spare dirt, which is fair enough. Then they started moving other dirt around and it looks like they are filling in their previous hole. I mean, it’s their hole, they can do what they want with it. I guess they just have a hobby that is stranger than most.
It is still a lot of hole. Strangely, their is a puddle of water on the bottom. At least it started as a puddle. I’ve been watching it grow over time, which is odd because there has been barely any rain. It has no right to grow, unless their is a secret spring hiding over there. If there were it would be a shame to build a condo on top of it.