Description for Cooper River
The Cooper River trail (1311) is a moderately technical, rolling river trail comparable to Skookum Flats and the Middle Fork Snoqualmie trail. Unlike the latter two, Cooper River is located in the drier forest on the east slope of the Cascades. You'll find lots of short ups & downs, with peekaboo views of Cooper River and Cooper Lake. This is an out-and-back ride.
(Technically, longer rides here combine two trails: 1311 Cooper River and 1323 Pete Lake, the latter up to the boundary of the Alpine Lakes Wilderness.)
Trail remains in prime condition in the summer since it's motorcycle free. Very popular with hikers and horses so be cautious. Snow free generally mid Spring to mid to late Fall.
Starting from the trailhead, the trail soon forks. Stay left. Trail climbs steeply with plenty of rocky rooty challenging terrain. The trail drops for a bit but you're soon climbing again as you climb above the river drainage into deeper forest. Eventually you drop down toward the river again as you descend thru some tricky rocky terrain. The trail levels from here to the forest road with several more smaller climbs and descents.
At the forest road take a right heading West/Northwest for about 30 feet, immediately drop in to trail to the left. This section of Cooper River Trail follows the road a bit, then drops into a primitive section of trail. Hard to follow at times the trail takes you through a section of creek, then spits you out along Owhi Campground along Cooper Lake. Here the trail becomes wide and smooth but there are several spurs that lead to assorted campsites to the left and right. Just keep following the widest path. (If you find yourself going up a switchback from the campground and end up climbing a decommissioned road, you're going the wrong way. Better wait for the ride leader or someone with a better sense of direction haha.)
After the campground the trail turns slightly primitive and has alot of twists and turns. Eventually ending on a forest road.
At the forest road just head West and you'll immediately find Pete Lake Trail, which continues to follow Cooper River above the lake. Some rocky sections, but quite a bit of twisty smooth trail. The terrain is much more level, yet there are still a few more short challenging climbs and descents left. After a short rocky climb to a big whale sized rock at the top. At this point there is a small spur trail to the South that leads to another larger rock. Here you can break for a quick peek at the snow capped mountains above, in the Alpine Lakes Wilderness.
As you resume there are a few options. The simpler one is to ride Pete Lake all the way to the wilderness boundary which has a sign and simply turn back. There are two spur trails that meander sharply up technical rocky trail to FR 4616 which parallels Pete Lake Trail. Both trails are tricky but manageable descents. Both spurs involve hike a bike when climbing, but the first one shortly after Tired Creek has more time in saddle than the second spur which ties back in at the wilderness boundary. Both trails take a sharp eye to find from the forest road. It would be my suggestion if you wish to try these trails to climb the first one, ride up the forest road and descend the second one, then return on Pete Lake Trail.