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INSTRUCTORS:
Chris Ramsey, PE
Philip S. Prince, Ph.D.
Brenden Stepek, PE
Stefan Flynn, PE, M.ASCE
Purpose and Background
These presentations were recorded at the Geo-Institute Web Conference 2025.
Subsurface Exploration and Emergency Response for I-40 Reconstruction in the Pigeon River Gorge Port Hurricane Helene (24 minutes)
Following devastation caused by Hurricane Helene throughout the western North Carolina region in September 2024, North Carolina Department of Transportation (NCDOT) reached out to the engineering community for the rebuilding process under an emergency condition. As part of the RK&K design team for the reconstruction of Interstate 40 (I-40), Schnabel Engineering developed an expedited and comprehensive investigation program for the first 5-miles (8 km) in North Carolina. I-40 experienced numerous failures along the five-mile corridor which is adjacent to the Pigeon River. In order develop repair concepts and ultimately to design the permanent repairs, a subsurface exploration program was established that included desktop review of historic geotechnical data, rock probes by air track drilling, rock probes by soil nail drilling, rock core sampling with standard coring methods, optical televiewer logging, and geophysical investigations using MASW methods. A suite of laboratory testing was performed to characterize engineering properties of the subsurface soils and rock. A large amount of data was gathered, and the need was recognized to keep the records in an organized fashion to streamline data review and meet the needs of an emergency response project where the design team and contractor’s team under an alternative delivery contract are working in unison. An internally developed database system (Mortar) that integrates different applications and services was deployed. Using Mortar, data mapping and integration is possible, facilitating a more informed design process.
Helene’s Debris Flows: Observations and New Questions (25 minutes)
This presentation will discuss his investigation of several debris flows that occurred during Hurricane Helene in 2024. In particular, passage of Hurricane Helene and the associated precursor rainfall event triggered thousands of slope failures in the southern Appalachian Blue Ridge from South Carolina to Virginia. Combined pre- and post-event lidar, aerial imagery, and intensive field investigation offer insight into trends in the behavior of both natural and constructed slopes within the impacted area. Debris flows initiating in colluvial soils produced the greatest impacts to life and property, with debris flows initiating on road embankments (both logging roads and engineered embankments) representing a notable component of severely destructive slope failure incidents. Natural slope debris flow initiation patterns agreed well with modeled debris flows susceptibility, though debris flow runouts often exceeded predicted lengths and widths. Helene's impacts highlight the need to improve debris flow susceptibility modeling, particularly runout modeling, with information derived from field-supported landslide inventories (e.g., soil type, bedrock-soil interface characteristics, surface runoff patterns) supported by high-resolution remote sensing datasets.
Emergency Response at Lake Lure Dam Following Hurricane Helene (28 minutes)
This presentation details the emergency response and engineering decision-making at Lake Lure Dam in western North Carolina following the extreme rainfall and flooding caused by Hurricane Helene. The speaker walks through the storm’s hydrologic impacts, including rapid reservoir rise, overtopping of historic dam features, and communication challenges during widespread power and infrastructure failures. Emphasis is placed on real-time risk assessment, coordination with emergency management agencies, and implementation of immediate stabilization measures under highly constrained conditions. The presentation also describes post-event inspections, subsurface investigations, and emergency repair design focused on abutment stability and internal erosion risk. Lessons learned regarding dam safety planning, instrumentation, emergency action plans, and stakeholder coordination are discussed. Attendees will gain insight into how dam safety professionals respond to rare, high-consequence events and manage uncertainty during crisis conditions.
Quantitative Assessment of Levee Breach Widening and Time-Rate Volume Loss Using Historical Overtopping Events (24 minutes)
This presentation presents a data-driven approach to understanding levee breach development during overtopping events using historical case studies. The speaker introduces the levee loading and incident database and explains how documented breach geometry, widening rates, and material loss were analyzed to identify common trends. Quantitative relationships are developed to better estimate breach growth and time-dependent volume loss, addressing key uncertainties in flood risk modeling. The presentation discusses how these findings can improve breach prediction methods used in risk assessments and emergency planning. Limitations of existing data and challenges in standardizing historical observations are also addressed. Attendees will gain insight into how empirical evidence can inform more reliable levee performance models under extreme hydraulic loading.
Benefits and Learning Outcomes
Upon completion of these sessions, you will be able to:
- Describe how geotechnical investigation methods and data management strategies are used to assess subsurface conditions and support resilient highway reconstruction following extreme flood events.
- Explain the mechanisms, triggering conditions, and runout behavior of debris flow landslides observed during Hurricane Helene in the Southern Appalachian region.
- Discuss the emergency response actions, engineering decision-making, and repair strategies implemented to manage dam safety risks during and after an extreme rainfall event.
- Identify key factors influencing levee breach development and volume loss based on analysis of historical overtopping events and quantitative data.
Assessment of Learning Outcomes
Learning outcomes are assessed and achieved through passing a 10 multiple-choice question post-test with at least a 70%.
Who Should Attend?
- Geotechnical Engineers
- Engineering Geologists
- Road Designers
- Practitioners
- Geosynthetic Manufacturers
- Contractors
- Graduate Students
How to Earn your CEUs/PDHs and Receive Your Certificate of Completion
To receive your certificate of completion, you will need to complete a short post-test online and receive a passing score of 70% or higher within 365 days of course purchase.
How do I convert CEUs to PDHs?
1.0 CEU = 10 PDHs [Example: 0.1 CEU = 1 PDH]