The tunnel operated until January 1943 , when miners working on the Kansas Lode near Nevadaville blasted into a water - filled mine working .
A large slug of water flooded out the tunnel entrance , killing the four miners .
The tunnel operated until January 1943 , when miners working on the Kansas Lode near Nevadaville blasted into a water - filled mine working , and a large slug of water flooded out the tunnel entrance , killing the four miners .