Jeremy Papasso, The Daily CameraBoulder Mountainbike Association volunteers Jenn Archuleta, left, James Shisler and Patrick Varga work to create a rock wall while working on the Aspen Alley Trail off Hall Road in western Boulder County on Sunday. The Boulder Mountainbike Alliance is using a $40,000 grant from Colorado Parks and Wildlife to build and repair trails south of Nederland, a six-week project that is part of the larger Magnolia Non-Motorized Trails Project approved by the U.S.