Peach, I have attempted to learn enough from those videos to figure out where the tree climbing took place. One possibility is Willamette National Forest, the closest accessible part of which is 60 miles south from Portland to Salem, then 48 miles east on Oregon route 22 to just west of Detroit OR. Another possiblity run by the Pacific Tree Climbing Institute is Oswald West State Park just north of Manzanita on the Pacific Coast. To get there from Portland it is about 75 miles WNW, including the last segment on local roads cutting southwest to Nehalem, just south of Manzanita. Given the time constraints of fitting between about 12pm estimated airport departure and approximately 5pm first place finish, I conclude that the task at the Cascade Locks area being east of Portland precludes going large distances either west or south.
There is a series of State Parks west of the Cascade Locks along US30. I believe that one of them should be the site of the tree climbing task. Possible state parks for this are:
Lewis and Clark
John B. Yeon
EDITOR's NOTE - A reference to Benson was removed as superfluous and distracting. I changed 4pm to 5pm finish time. I added Rooster Rock, John B. Yeon and Viento State Parks to this list from examining the map for hard-to-read information.