It's been years but I used to cross the bridge at Tenino and go east and explore all the side roads towards the river. There was a plumb creek timber road that went down to the river and ended up just across from that Private Camping/Fishing park on the north side of the river. It was pretty rough and steep 4x4 only road. I wish I could tell you the road it was on, but it's been too long. It is in the Gazetter. You'll have to do a little exploring, but I fished there quite a bit and never saw another person. Good Luck.