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1 Unstable slopes affect almost every state in all types of geographies, whether the slopes are owned embankments and cut slopes or hazards originating from beyond-the-right-of-way. For several decades, geotechnical instrumentation and monitoring technologies have been used to inform safety, operational, and treatment decisions for these slopes. The types of instrumentation and monitoring technologies range from devices installed on or in slopes to remote-sensing methods from ground, aerial, or satellite-based systems. Through these technologies, state departments of transportation (DOTs) collect data that determines the timing and scale of slope stabilization projects, alerts travelers and maintenance professionals of sudden hazardous conditions, and provides confidence in decisions to defer treatment actions and accept risk. Across state DOTs, technology advancements and digital transformations are a constant for nearly every process and system and this observation is true for unstable slope instru- mentation and monitoring technologies. Advancements in slope instrumentation and monitoring technology provide opportunities to improve safety for workers and travelers, reduce operational disruptions from unstable slopes, and optimize cost and risk tolerance decisions over the life-cycle. The objective of this synthesis is to document the current state of practice in DOTs for geotechnical instrumentation and monitoring of unstable slopes with a focus on the application of new technologies and improvements implemented in the last decade. Information was collected through a review of domestic and international literature, a survey of state DOT geotechnical engineers and geologists, and follow-up interviews with selected agencies for development of case examples. The synthesis survey questionnaire was sent to DOTs in all states and the District of Columbia and Puerto Rico. The response rate for the survey was 84% with a total of 43 state agency responses received. Following the survey review, the state DOTs in Vermont, Maryland, Minnesota, and Oregon were contacted for follow-up interviews for the development of case examples. The synthesis found that remote sensing for unstable slopes is a technology showing a rapid rate of advancement and also a technology that is seeing many first-time uses within the last 10 years. DOTs have made increasing use of ground-based geotechnical instruments in the last decade. The findings indicate that this increase is occurring primarily through the greater adoption of existing instrumentation technology that has been available for more than 10 years. With respect to data and data management, the study findings indicate the use of electronic-based methods has increased in the last 10 years for DOTs through technology advancements related to remote viewing of near real-time and recorded data, web-based S U M M A R Y Advances in Unstable Slope Instrumentation and Monitoring
2 Advances in Unstable Slope Instrumentation and Monitoring access or presentation of data, onsite data acquisition, and transmission of data offsite via wireless (radio, cellular, etc.) telemetry. Over the last decade, approximately one-third of the DOTs indicated they have implemented web-based platforms to access data from site- specific systems. The synthesis results indicate that existing and proven instrumentation technologies are not fully utilized. Based on information learned from the case examples and from the literature, using processes that evaluate and communicate the benefits of new and existing technology can be an effective means for improving the utilization of instrumentation and monitoring systems.