RAPID CITY, S.D. (KELO) — A recent study released by a law firm in Rapid City did not rule out the chance the old gypsum mine extends under Interstate 90.
The 34-page report from Montana Technical University was made public by Fitzgerald Law Firm. Geological Engineering professors Mohammadhossein Sadeghiamirshahidi and Mohamed Khalil wrote the report to “determine the extent of the abandoned gypsum mine.” You can read the full report below.
The study says the first report on the underground Black Hawk mine was from the state mine inspector in 1912. The mine was operated by the Dakota Plaster company and the study highlights past and present known mining activities in the area.
Among the highlights, the report says the west boundary of the mine is Daisy Drive and “results show that it is very likely that the mine extends well beyond the known (mapped) areas on the northeast, east, and southeast side. Based on the information obtained in this research, there is also the possibility that the mine extends below the interstate.”
In Aug. 2020, the South Dakota Transportation Department said the sinkhole in Black Hawk was no longer a danger. Test results revealed none of the areas identified as anomalies were a void or anything else that would cause concern for the integrity of the Interstate 90.
Test results revealed none of the areas identified as anomalies were a void or anything else that would cause concern for the integrity of the Interstate 90.
The report concludes more studies should occur especially on the northeast and east side.
A news conference with the researchers from Montana Tech is scheduled for June 28.