Went to the top of Butler Valley. Ride stats 26.5miles in 1hr34mins. I follow the rolling river bank of the Mad River on West End Road between Blue Lake and Arcata. Today I was holding down 27mph for part of this section.
The climb is only 3miles up from Korbel, but "an average 8% grade for approximately 2.6 miles and gain about 1100 feet in elevation." (northcoastbikerides.blogspot.com)