Blue Mountains, Oregon Whitwater Rivers Grande Ronde River Class II-III - 19.5 miles long (Troy to Boggan's Oasis) Asotin County Grande Ronde River Class II - 8 miles long (Red Bridge State Park to Hilgard Junction State Park) Union County Grande Ronde River Class II-IV - 9 miles long (Hilgard Junction State Park to Riverside City Park) Union County Grande Ronde River Class II-IV - 17 miles long (Tony Vey Meadow to Red Bridge State Park) Union County John Day River - North Fork Class II-III - 41 miles long (Route 52 Bridge to Dale) Grant/ Umatilla County John Day River - North Fork Class II - 44 miles long (Dale to Monument) Grant County