About a dozen of properties in Black Hawk, South Dakota, got evacuated after  one sinkhole opened under the Hideaway Hills development. On the 27th of April, the ground started to lose its strength and it has left locals with uncertainty.  Although the situation has led to a unique discovery. The residential properties in Black Hawk were built on an abandoned gypsum mine.

The authorities of the area are working on figuring out how this could’ve happened. In the meantime, nearby explorers of a local caving group called Paha Sapa Grotto took initiative to discover what’s under the sinkhole.

The Paha Sapa Grotto is a subunit of the National Speleological Society, and is amongst the world leaders in caving science, conservation and exploration. “When we heard about the sinkhole, we knew it was on a geological unit that could potentially have caves in it,” Nick Anderson, a member of the group, told Hiptoro. “We also knew that county emergency management wouldn’t have much experience in this area so we offered to help to determine the scope of the problem.”

“Upon entering, we immediately realized that it was an abandoned gypsum mine and not a cave”

“The room we entered was 15 feet tall and 60 feet wide. We got a quick look around and exited”

The team leader who went inside the cave is the Vice-Chairman of the Paha Sapa Grotto. He is also the Director of the National Speleological Society (NSS), Adam Weaver.

“On the assessment trip, I went out there with Nick Anderson and Dave Springhetti. When we got to the site, the roads were buckled and the guy who lived in the house next to the sinkhole, John, nicely told us to park further away because we just didn’t know what was happening yet,” Weaver explained. “After some general looking around, we found a fence that seemed sturdy enough to rig the rope to and I rappelled into the hole. These photos you saw of me on the rope are from that initial rappel. When I got to the bottom, I could see 80ft into a large cavity that was at that point under the street. I stopped going forward because the sidewalk and street were bent down and cracked.”

However, we must remember that till this point, Paha Sapa Grotto considered that it might be a cave. So. Weaver was full of excitement to make a big discovery. “When Doug from emergency management showed up, I told him that we could safely go in if they could pull the cracked concrete off of the hole. Soon, they had a piece of machinery there and with the sidewalk gone, we felt much safer about going in. Nick, Dave, and I went in, and it was immediately obvious that it was a mine. There were a lot of drill holes and old mining debris. On this first visit, I made a quick sketch map of what we could see (about 500ft of mine) and then took it to show the people on the surface. I think that’s when the severity of the issue really set in with a lot of people. I also told them that I would come back with two teams the following day and bring correct gear to correctly map it,” the caver said.

The cavers returned the next night. This time, there were two teams of explorers, equipped with survey gear and ready to map the mine


“We determined that the mine was over 2K feet across and over 150 feet wide. It went directly under at least 12 homes”

However, even the Paha Sapa Grotto couldn’t safely explore all of the corners of the sinkhole

“The full extent of the mine is still unknown as passages are either collapsed in, flooded, or too dangerous to enter”

The not so good part of this entire episode is that the Federal Emergency Management Agency (FEMA) made a statement saying the residents won’t be getting any of its grants. “Unresolved issues regarding whether this is a natural event, the likelihood of negligence, and the duplication of federal benefits”.

Residents of the Hideaway Hills subdivision are suing South Dakota, Meade County, and developers of the subdivision for more than $75,000,00

The lawsuit on behalf of 119 homeowners also includes counts against title companies involved in sales of the homes, attorneys for previous owners, and real estate agents who sold the homes

The residents are seeking more than $35,000,000 in compensatory damages, $40,000,000 in exemplary damages, and “such other relief as the court deems equitable”

Here’s what people said about the whole ordeal

What are your thoughts about this incident? Would you be scared if something like this occurred in your surroundings? Share your thought with us in the comment section.