Study: Abandoned gypsum mine could extend below South Dakota interstate

South Dakota News

FILE – In this April 1, 2015 file photo, a semi-truck passes by a newly posted 80 mph speed limit sign on Interstate 90 near Brandon, S.D. Travelers on a roughly 55-mile stretch of I-90 west of Rapid City to the Wyoming border may not be able to drive the new 80 mph speed limit for much longer under recommendations proposed by the Department of Transportation. The state Transportation Commission will take public comment during a hearing at the end of May on the proposal, which would drop the speed limit long-term on that portion to 75 mph. (AP Photo/Kevin Burbach, File)

RAPID CITY, S.D. (AP) — A study shows that an abandoned gypsum mine in Black Hawk that was exposed by a sinkhole in 2020 may extend farther than current mapped areas would indicate.

Mohammad Sadeghi, a professor of geological engineering at Montana Technical University who led the study, says there’s the possibility that the mine extends below Interstate 90.

The group recommends that further research be done in the area. More than 40 people from 15 homes in the Hideaway Hills neighborhood were forced to evacuate after the collapse in April 2020 in Black Hawk, which is located about eight miles northwest of Rapid City.

The Rapid City Journal reports there are at least two lawsuits filed in relation to the collapse, one of which is one step closer to class-action status.

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