Imagine mowing your grass one afternoon, when suddenly you feel the ground drop and a giant hole opens up where your driveway used to be. That's what happened last week in Blackhawk, South Dakota when a large sinkhole appeared in the neighborhood.

According to the Rapid City Journal the sinkhole has caused the evacuation of a dozen homes, displacing 30 - 50 people. You don't hear about too many sinkholes in the Rocky Mountain West. The USGS says "most damage from sinkholes tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania."

Credit: Land Subsidence in the Unites States, USGS Fact sheet 165-00

 

What caused the sinkhole in the Rapid City suburb last week? Get this... an abandoned gypsum mine. That's right, there is an old mine from like a 100 years ago about 40 - 60 feet underneath the subdivision. The mine is at least 600 feet long x 150 feet wide and is now - obviously - partially collapsed. The property owners say their home insurance doesn't cover sink holes (of course it doesn't), and I imagine the owners of these houses (built in 2005 on what is now extremely unstable ground) are looking for answers.

If you've ever sold property, you know you are required to disclose any material defects or known issues with the property. In my opinion, it may be tough for the developer to claim they were unaware of the abandoned mine when they bought the land and started building a subdivision on top of it. We'll see how it will play out - likely in court.