all near deadwood / keystone SD

https://en.wikipedia.org/wiki/Sanford_Underground_Research_Facility

Sanford Underground Research Facility

REMINDER

https://www.thedickinsonpress.com/news/crime-and-courts/6639203-T.-Denny-Sanford-namesake-of-health-network-subject-of-child-pornography-investigation

SURF is located in the former Homestake Gold Mine and encompasses 223 acres on the surface and 7,700 acres underground. The surface property includes both the Yates Campus and the Ross Campus, named respectively for the Yates and Ross Shafts, which provide access to underground areas. The property was donated by Homestake’s parent company, Barrick Gold, to the SDSTA for use as a dedicated research facility in 2006. [20]

Homestake carved out more than 370 miles of underground shafts, drifts and ramps, and Sanford Lab currently maintains about 12 miles for science activities. The main level for science is the 4850 Level, which can be accessed through the Yates and Ross shafts. At 1,490 meters, SURF is the deepest underground laboratory in the U.S. For experiments on the 4850 Level, the average rock overburden is approximately 4,300 meters water equivalent (m.w.e.). This depth provides significant protection from cosmic radiation from the sun for sensitive particle physics experiments. [2]