Rapid City engineering company investigating possible mine activity under I-90
BLACK HAWK, S.D. — A Rapid City engineering company has been chosen to investigate possible mine activity beneath Interstate-90 in Black Hawk.
It’s been about a month since an old gypsum mine was exposed under the Hideaway Hills subdivision, forcing the residents to leave their homes.
The state has hired FMG Engineering to look for “underground anomalies” beneath the interstate. That work could begin as soon as May 26.
FMG will use what’s called “electrical resistivity” to explore what lies beneath.
“One probe will talk to the other and they’ll communicate, what they call communication, so if there is no communication that means there is a void there,” said Mike Carlson, a Department of Transportation Engineer. “If the communication is fast it could mean that it’s water. So they will know based on how quickly they communicate as to what is the underlying material”.
A company from California will also be helping in the investigation. DOT has been regularly checking the interstate for issues. There haven’t been any, so they remain confident the interstate has not bee effected by the old mine.