Unusual Garter snake found in OR

[snowfyre]

Hi, this is my first time here and I would like to pick your brains. I work at a petstore and I often get called to ID or evaluate snakes brought into the store. This snake was found at an apartment. <pretty sure not its native environment> It is a black snake. I had to search around to figure for sure if it was a garter snake. I am guessing that this is a melanistic garter snake. After looking at some of the usual snakes for this area, I'm leaning toward the western terrestrial snake due to the pattern I can see behind the black. Either way, any help would be appreciated! Here is a link to the album I made for the snake. If there is any other information I can help supply, I'll do my best.

Location:Hermiston, OR

Blackgartersnake pictures by Snowfyre - Photobucket


Apparently the snake does a great job of playing dead or so the apartment owner says.