Flooding the Cloakwood Mine is a "feeder" quest for the Chapter 4 story-line. It is initiated by speaking to either of two unnamed Miners in the first subterranean Cloakwood Mine level. The more important of the two is found at 1975, 245. The other is found at 350, 1850. Talk to Rill with Key to River Plug in your possession to flood the mine.