I think there are some directions on the board some where but here is a rough version:

I'm closer to the 880 in San Jose but then I head north to 80, take the San Rafael/Richmond Bridge, hit 101 north, once in Santa Rosa take Highway 12 exit towards Sonoma. From there you'll come to a light where the freeway ends. Go straight through the light and follow the road till you come to an intersection where you will see houses in front of you. Go straight through to the residential looking area, take a left at the first stop sign then follow the road all the way back where you'll hit the pay station. Take a left towards the dam and you're there! It is about 95 miles from the 237/880 intersection.

Hope this helps and hopefully someone will post a map. Gotta run so give a little help out there!

Todd