Concerns that more layers of rock might peel away from the roof of Spruce Tree House at Mesa Verde National Park in Colorado has prompted officials to keep the cliff dwelling closed to the public for the immediate future.
It was last August when a rock fall at Spruce Tree House led to closure of the southern portion of the site for visitor safety. After a hazard assessment was conducted, it was decided that the entire site should be closed to the public in October 2015.
In November 2015, a select climbing team comprised of National Park Service employees from Chiricahua National Monument, Rocky Mountain National Park and Arches/Canyonlands National Parks completed a technical scaling project at Spruce Tree House. At this time, the arch crack system above Spruce Tree House was inspected and any loose material was removed; however, other rock fall concerns were identified during this process, and Mesa Verde has determined to keep Spruce Tree House closed for the foreseeable future, until a full geotechnical assessment can be performed, a park release issued Tuesday said.
Spruce Tree House may be seen from an overlook near the Chapin Mesa Museum. Rangers will provide guided talks through March 5. After that date, rangers will be available at the overlook to answer questions. The Petroglyph and Spruce Canyon hiking trails will be accessible by the traditional vantage point, south of Spruce Tree House.
A natural sandstone arch is present in the Spruce Tree House alcove, just above the cliff dwelling. Early stabilization work was performed in the 1940s, with additional stabilization work completed in the 1960s. Natural erosion processes, including the settling of the arch, have been affected by the early stabilization work, so that modern engineering techniques may be necessary to ensure continued stability of the arch.
Spruce Tree House is the third-largest cliff dwelling in the park. As one of the best preserved ancestral Pueblo sites in the Southwest, there are many examples of original architecture including intact roofs, floors, and original plaster designs in the dwelling. Due to the accessibility of the site and its self-guided access, it is the most-visited cliff dwelling in the park.
Due to the complexity of the project and the significance of Spruce Tree House cliff dwelling, there is a four-phase sequential approach planned. The first phase is to use Light Detection and Ranging (LiDAR), a remote sensing method employing a laser to obtain a complete structure profile. Also, geotechnical information will be collected to be integrated in the numeric modeling and analysis. Phase Two will consist of geotechnical engineers conducting detailed three-dimensional computer-based analyses of the original condition, 1960s stabilization and probable 2016 stabilization, using information from Phase One as a chronological modeling sequence. Phase Three will include developing plans, specifications, and gathering necessary information to complete stabilization work. Phase Four will be the performance of that work.