In 2018, ACE Southwest began work on the Mount Sanitas Trail in Boulder, Colorado. Mount Sanitas Trail is a moderate to difficult trail which travels along both sides of the ridge, leading to the summit of Mount Sanitas. The steep grade of this trail has exposed the tread to heavy erosion over the years, which leads to loose rocks and dangerous conditions. The ACE crew in 2018 worked alongside the Boulder City Open Spaces and Mountain Parks team, to build an expansive rock staircase which totaled 39 rock steps being installed. The crew also put in a 228 square foot retaining wall. In 2019, the crew was led by ACE crew leader Kiersten Bonesteel and ACE project manager Sam Richards. This season 28 new steps were installed approximately a mile up the trail.Through the use of highlines and advanced rigging systems, the crew members moved rocks across the ridge and placed them to define the trail and create a more sustainable path to the summit. Using multiple grip-hoists and walkie talkies, crew members communicated with each other to execute successful rock movements. Once the rocks were relocated, crew members used rifting hammers, hammer points and other tools to shape and fit the rocks to sit securely in their place. This work is extremely technical and requires patience and clear communication between crew members but the results speak for themselves. ACE is thrilled to have finished another successful season of working with the City of Boulder Open Spaces and Mountain Parks and looks forward to the future of this partnership.