Hi,

The tick in your photo is an adult male from the genus Dermacentor. Two Dermacentor species most likely to be in the Gorge are the Rocky Mountain wood tick (Dermacentor andersoni) and the western dog tick (Dermacentor similis). I can't tell the species of your specimen from the photos though. I'd have to look at it in person under a microscope.

Luckily, no ticks in the genus Dermacentor transmit Lyme disease, so you don't need to worry about that. Dermacentor ticks can transmit other diseases such as Rocky Mountain spotted fever and tularemia to people, but cases of these diseases being transmitted by tick bites in OR are extremely rare. I don't know if/how these diseases might affect dogs.

Hope that helps!