Lucidum

I currently live in Ashland, Oregon, and a few weeks ago I heard a friend mention seeing a garter snake in the local park. Now I haven't seen anything myself, but it's the right kind of environment for garters. I know they brumate during the winter (which is approaching quickly), and that they brumate below the frost line, but I'm looking to collect some of the snakes while brumating, so I can breed them and enjoy studying them in captivity. Does anyone know where I should look for Garter snakes brumating?