We tried to do the loop clockwise starting at the Goat creek trailhead, which is northwest of the loop (trails 205, 218 and 217). I read it was just under 18 miles. However, as soon as we got from trail 205, 218 was LITTERED with blown down branchy trees and root wads that sucked to get through. We probably dismounted every 50-100 yards. We fought through the trail past the creek crossing heading up toward Tumwater Mountain but only made it maybe  another half mile uphill before we decided it wasn't worth going further, since the blowdown situation could be just as bad throughout the remaining ~15 miles. The waterfall/cave feature on 205 is awesome! 

Id strongly discourage anyone from riding this part of trail (from 205 & 218 junction up toward Tumwater Mountain) based on what I saw, until some work is done. If cleaned up, itd be on the top of my list. The clear sections were a blast and the surroundings/terrain are supreme.

And just a heads up, there's definitely some exposure.