I was camping at the Forest Service's Mendenhall Lake Campground and discovered this trail as I ventured out of the campground. The trail can be accessed at the end of River Road off of Back Loop Mendenhall Road. The trail is only 2.5 miles long but runs through a lovely old fern-filled forest and parallels Mendenhall River. The official name of the trail is Kaxdegoowu Heen Dei (Clear Water Creek Trail).
The photo below shows Mendenhall Glacier in the distance and the mountains towering over it, with red fireweed plants in the foreground. You can also access the trail on Egan Road, just north of Mendenhall Loop Road by Industrial Avenue (which is where this photo was taken). Though the trail is very short, it connects with the Mendenhall Loop Bike route which in some places is a wide, paved path near the road, and at other places is a wide shoulder marked for bikes. This in turn connects with Egan Road/Glacier Highway Bike Path which can take you all the way to downtown Juneau.