Zion National Park Unstable Slope Assessment Report, Geotechnical Report No. UT-NX-USMP-20-01

Department of Transportation

This report summarizes the results of Federal Lands Highway Division’s (FLHD) preliminary assessment of the priority unstable slopes in Zion National Park (ZION), Utah. The Unstable Slope Management Program for Federal Land Management agencies (USMP) (January 2019) was utilized for this assessment. The purpose of the assessment was to verify the ratings for those unstable slopes rated higher than 400 points for current conditions and develop conceptual level risk reduction and/or full mitigation alternatives with geotechnical cost estimates. This work will provide ZION with information that will be needed to develop benefit/cost analyses for each unstable slope site and allow the Park to consider the alternatives for each site when more than one is provided. In depth benefit/cost analysis could further prioritize unstable slopes for risk reduction work however, the conceptual risk reduction alternatives provide an opportunity to schedule risk reduction work along with other facility maintenance or as standalone projects using the initial USMP prioritization.