Google "Durham Animal Control".
Alternatively get a big box, trap him, and relocate him yourself. It's likely, though, that whatever attracted the snake to your hard is likely to attract other snakes once he's gone.
Before you do anything you need to identify it. It's probably not a dangerous snake, but you really need to make sure.
See you back here in a couple of months when you want to know who's responsible for removing the rats!