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Geosynthetic clay liners (GCLs) used in waste and chemical containment applications exhibit high swell and low hydraulic conductivity to water (e.g., k < 10−10 m/s), such that diffusion dominates contaminant transport occurring through the barrier. Thus, knowledge of expected diffusion coefficients for GCLs under relevant environmental conditions is required for performance-based design and accurate assessment of the barrier system. Unfortunately, diffusion testing for bentonites can be challenging and time consuming, limiting data availability for GCL diffusion coefficients. The dialysis leaching test (DLT) method has been utilized in recent studies for simple, time-efficient diffusion measurements for bulk sodium bentonites (NaB), enhanced bentonites, and NaB pastes. This study used a new, modified version of the DLT method for measuring diffusion in GCLs comprising NaB. Diffusion tests were performed using dilute (20 mM) and aggressive (100 mM) calcium chloride (CaCl2) solutions to measure apparent diffusion coefficients (Da) for chloride for the GCLs. Values of Da were in the range of 10−10 m2/s, consistent with expectations from the literature for longer-term traditional testing. Diffusion coefficients increased as CaCl2 concentration increased, as expected due to cation exchange and suppression of the diffuse double layer in the bentonite in the GCL. The results of the study demonstrate the potential use of a new, time-efficient test method for assessing diffusion properties of GCLs, further improving our ability to predict contaminant transport through barrier systems. 

In Fall of 2024, central Florida was impacted by Hurricane Helene (landfall in Perry, FL as a Cat 4 hurricane on Sept 27) and by Hurricane Milton (landfall in Siesta Key, FL as Cat 3 on Oct 9). The hurricanes led to damages of an estimated value > $200billion. The Nearshore Extreme Events Reconnaissance Association (NEER) and the Geotechnical Extreme Events Reconnaissance Association (GEER) represented by their members from more than 10 academic institutions, federal agencies, and industry and supported by technical staff from the NHERI RAPID facility and the UF Center for Coastal Solutions initiated on Sept 23 a data collection effort that included pre-, during-, and post-storm multi-disciplinary data collections efforts. The field data collection effort was concluded on Nov 22. Data includes hydraulic information on storm surge, waves, and currents, topographic and bathymetric data sets, terrestrial and seabed mapping, and geotechnical site characterization including in-situ testing, sediment sampling, and seismic testing. Data was collected in four focus areas in Florida (Cedar Key; Horseshoe Beach; Midnight Pass and Milton Pass, both near Venice) and observational data and limited data products were collected in other areas in Florida including Orchid, Ponte Vedra, Suwannee, Panama City, and others. Data is organized by site (four primary sites and others); data collection phase with respect to the two hurricanes; and instruments or data collection method. This work included support from both the UF Center for Coastal Solutions and the NHERI RAPID facility. 

In June 2022, the southern part of Montana and the northern part of Yellowstone National Park experienced flooding along multiple watersheds, including the Yellowstone River. The flooding resulted from heavy snowmelt between June 10-13th, leading to record levels of river water elevation in most of the main tributaries to the Yellowstone River. Substantial damage occurred to residential, commercial, and transport infrastructure, however, no fatalities were reported. Estimated damages accumulate to approximately U.S. $29 million. The GEER reconnaissance effort, conducted between June 30th – July 4th, recorded geotechnical, geo-structural, and geomorphological observations of failures as well as successful mitigation of flood damage. In addition to traditional terrestrial photography and aerial imagery, the team collected (Light Detection Ranging (LIDAR) scanning, Structure for Motion (SfM) imagery, and Multispectral Imagery to establish point cloud models for case history analyses and post-reconnaissance failure analyses. 

Reconnaissance following Hurricane Ida. Wind damage to light structures, flooding, levee failures, coastal erosion. Field photos, Lidar, UAVs.