The road network within the state of Utah is contained within a diverse suite of terrain, which in some areas presents substantial rock fall and slope stability hazards. With projected future increases to the traffic load on Utah's roads in mind, a project has been initiated by Utah Department of Transportation (UDOT) to implement a rock fall hazard investigation statewide. An existing model used by the Oregon Department of Transportation during the mid 1980s known as the Rockfall Hazard Rating System (RHRS) has been adopted as a starting point for developing a program in Utah. During the summer of 2001, Phase I of the RHRS was conducted statewide in order to classify road cuts into three categories in order to prioritize them for future study. Over 800 road cuts were inspected in the field and given a rating of either A (immediate potential for rockfall danger), B (moderate rockfall potential), or C (Low potential for rockfall) based on RHRS criteria. Following the completion of these field ratings, a GIS database was constructed for all A & B-rated cuts statewide and includes basic descriptions, locations, and photographs of the sites. Following input from UDOT, a more detailed Phase n survey is planned for the summer of 2002, which will include "A" rated slopes for individual detailed studies resulting in a detailed database that can be directly applied to prioritization of future mitigation efforts. The detailed investigation will attach numerical ratings in twelve categories for each of the A-rated slopes with the highest overall ratings corresponding to the most likely rockfall sites. Rating criteria vary from purely subjective categories to ones that are numerically based. The rating system describes both the slope geometries and geologic conditions at each site and relates these to rockfall concerns on the roadway itself. Allowances are also made to reflect traffic density at any given site. The twelve rating categories will initially be based on the RHRS system but may be modified to better fit the conditions of Utah roads at some point during the study. It is anticipated that this detailed portion of the field study, will be partially completed in the summer of 2002 and data generated from this made available to UDOT before the end of the year.
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