Soudan 2 was the successor to the Soudan 1, a similar 30 ton detector also intended to search for proton decay.
The excavation for Soudan 2 was done in 1984–1985. Installation was started in 1986 and was completed in 1993. The experiment was run from April 1989 to June 2001, beginning with a partial detector of 275 tons. It was disassembled in 2005 to make room for further low background physics experiments, including MINOS.
^http://ccdb4fs.kek.jp/cgi-bin/img_index?8203219 "The Soudan Nucleon Decay Program", D.S. Ayres. ANL-HEP-CP-82-03, Presented at Workshop on Physics and Astrophysics with a Multikiloton Underground Track-Detector, Rome, Italy, 29-31 Oct 1981.