This is a prophecy that's still developing, and grow as more is learned or discovered. But basically what it's talking about is the eventual catastrophic failure of the Oroville Dam in California. There's no real way to know if this failure will occur on its own, or if it'll be part of a larger event, such as the west coast super quake that's predicted to occur.
(*Do you have a better description, or did you find an error? Please let me know.