My GPS sent me south on Bagby road then U-turn and back up through this difficult intersection. It says right turn in 100 feet. This must be it. I never would have found this "trail" on my own.
Sunday, August 1, 2021
45.423180555555554, -122.744775
google map 
BOUNDARY 45.4195342, -122.7526903
BOUNDARY 45.4282157, -122.7361418