Opening Remarks 

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1:05 - 1:45 p.m.

Fiber Optic Distributed Sensing as a Window on Subsurface Flow

Matthew Becker, California State University Long Beach

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The advancement of fiber optic distributed sensing over the past two decades has enabled the measurement of subsurface hydraulics and geomechanics at unprecedented temporal and spatial detail.  Fiber optic distributed sensing systems operate by firing laser light down a fiber optic cable and using backscattered photons to measure temperature, vibration, or strain.  Kilometers of measurements can be made at scales as small as a centimeter and at sampling intervals of less than a millisecond.   We will look at how this technology has improved our understanding of subsurface flow related to diverse applications such as stream discharge, managed aquifer recharge, remediation of contaminated sites, aquifer testing, fracture hydromechanics, and energy resources.  As these instruments become more reliable, accurate, and economical, opportunities for revolutionary observations of groundwater systems will continue to expand in the coming decades.

Co-authors: Dave Walsh (Vista Clara Inc.)
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1:45 - 2:05 p.m.

Building Reliable Groundwater Transport Models at Contaminated Sites Using Cross-Borehole Electrical Monitoring

Léa Lévy, Lund University

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Industrial application of environmentally hazardous substances have led to contamination of important groundwater aquifers worldwide. Several remediation techniques exist, such as excavation, pump-and-treat, and in-situ remediation. Excavation is effective but it is associated with significant pollution and resource use, especially below a couple of meters depth. In situ remediation technologies, considered less invasive, are discussed here. They rely on the installation of a treatment zone, where a reactive agent is injected to chemically and/or biologically degrade the contamination. 

Reliable transport models at contaminated sites are essential both for predicting the long-term fate of contaminants and for understanding the effectiveness of in-situ remediation actions. In the short-term, preferential pathways, and more generally permeability contrasts, might lead to incomplete contact between contamination and reagent. This increases the risk of insufficient treatment followed by rebound effect, where contamination starts diffusing back into more permeable zones after remediation, resulting in an aquifer still contaminated in the long-term. In the long-term, preferential pathways may play an important role in the contaminant mass discharge.

Here, we compare different approches for evaluating transport properties, based on cross-borehole electrical tomography for both characterization and monitoring, as well as on chemical monitoring and sediment analyses. The first approach consists in using cross-borehole induced polarization data for inverting the permeability field before remediation takes place. The second approach relies on inverting preferential pathways as discrete 1D elements, ”fractures”, based on time-lapse cross-borehole resistivity monitoring of the injection. The third method is a coupled hydrogeophysical inversion of the permeability field, using a stochastic optimization of the permeability distribution that includes misfit calculation with both concentration data and resistivity data at different time steps. The three approaches are tested on the same dataset, collected during a remediation experiment at a contaminated site in Farum, Denmark (suburb of Copenhagen).

Coauthors: Line M. Madsen (Aarhus University), Delphine Roubinet (University of Montpellier), Léa Lelimouzin (University of Montpellier),Chloé Delbet (Sorbonne University), Thomas Günther (Leibniz Institute for Applied Geophysics), Poul L. Bjerg (Technical University of Denmark), Nina Tuxen (Capital Region of Denmark)
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2:05 - 2:25 p.m.

Spectral Induced Polarization Monitoring of Carbon-Based Remediation in DNAPL-Contaminated Groundwater 

Angelos Almpanis, Western University, Canada

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Colloidal activated carbon (CAC) filters are becoming a popular option to remediate groundwater contaminated by dense non-aqueous phase liquids (DNAPLs) and a real-time monitoring approach is desirable to assess its effectiveness. In this study, the spectral induced polarization (SIP) technique is evaluated for its applicability as a monitoring tool for DNAPL adsorption within CAC-filters. The adsorption of low-concentration (50 mg/L) tetrachloroethylene (PCE) in a CAC-filter was examined using a set of dynamic column experiments combined with SIP monitoring. The initial flushing of CAC into inert porous media was tracked by SIP monitoring, with an increase in both real and imaginary components of the complex conductivity. The CAC was then flushed out of the column via groundwater, leaving behind only carbon particles that will later adsorb the PCE. The process of flushing the CAC by groundwater indicated a decrease in both the SIP real and imaginary conductivities, with the imaginary holding a small amount of polarizability, which is likely associated with the remaining carbon particles. Finally, dissolved phase PCE was injected through the column, with insignificant changes in the simultaneous SIP response. This study suggests that SIP can monitor CAC within porous media but is insensitive to the low concentrations of dissolved phase PCE. 

Coauthors: Lee Slater (Rutgers University, USA), Christopher Power (Western University, Canada)
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Open Discussion

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Posters and Vendor Exhibit

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3:15 - 3:35 p.m.

NMR Logging Technologies for High-Resolution Site Characterization and Monitoring of Environmental Remediation

Dave Walsh, Vista Clara Inc.

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Nuclear magnetic resonance (NMR) is a powerful non-destructive and non-radiative methodology that is widely used in a variety of disciplines, such as chemistry (high field NMR spectrometers) and medicine (MRI scanners). In Earth sciences, NMR allows direct detection of hydrogen in subsurface pore spaces. The detected NMR signal allows quantitative determination of the volumetric water content and saturated porosity, which further indicates the pore size distribution and hydraulic conductivity. In environmental remediation, the NMR logging technology can be successfully used for high resolution site characterization (HRSC), soil moisture and bio-geochemical processes monitoring, permafrost examination, etc. 
In this meeting, we will expose the audience to NMR technology in general and present available tools and their applications in environmental remediation. In addition, we will present results of our recent work at Moab Uranium Mill Tailings Remedial Action (Moab UMTRA), where we used unattended borehole NMR technology to monitor longitudinal changes in water signal associated with progress of hydroxyapatite precipitation. 
In summary, the audience of this session will gain a valuable understanding of innovative, non-destructive, highly sensitive, and currently available NMR technology for groundwater applications and their potential in a variety of environmental remediation projects.

Coauthors: Darya Morozov (Vista Clara Inc.)
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3:35 - 3:55 p.m.

Locating Undocumented Orphaned Oil and Gas Wells with Cost Effective UAVs

Sina Saneiyan, University of Oklahoma

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The majority of the estimated 3 million abandoned oil and gas wells in the U.S. have missing documents and lack surface equipment making them difficult to locate. However, most of these well have casings made of iron alloys which are magnetic and can be sensed by magnetometers. Here we utilize an iPhone 12 mini smartphone as a magnetometer to locate two abandoned wells. We designed a simple unmanned aerial vehicle (UAV) survey setup where the iPhone 12 mini was hung from an inexpensive small drone. We surveyed the two sites by flying the drone at altitudes, 10 m, 15 m, and 20 m above ground level. Our results show that at the altitude of 10 magl the smartphone magnetometer could pick the magnetic anomaly of either of the wells at intensities ≥ 52 μT; sufficient to accurately locate the wells. At the altitude of 15 magl the smartphone could locate the wells within ~5 m radius of the actual wells’ location, and it was unable to detect any magnetic anomalies at 20 magl. The simplicity of the setup, minimal required scientific knowledge, and low cost of the setup makes it an ideal tool for locating orphaned wells by citizen scientists.

Coauthors: Danial Mansourian (University of Oklahoma)
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3:55 - 4:15 p.m.

Using Digital Twinning to Plan Environmental Characterization and Remediation

David Yuke, Canadian Nuclear Laboratories 

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Canadian Nuclear Laboratories (CNL), manages Canada’s nuclear legacy liabilities on behalf of Atomic Energy of Canada Limited (AECL) and the Government of Canada.  Operating under a Government Owned - Contractor Operated (GOCO) model, CNL has accelerated its environmental clean-up mission, the largest and most complex decommissioning and environmental remediation program of work in the country.
CNL is currently executing clean-up work at six different sites across Canada.  The largest site and the main campus of CNL is at the Chalk River Laboratories (CRL) and is home to various waste management areas and affected lands in various stages of environmental remediation. 
The Liquid Dispersal Area (LDA) pipeline, operational at the CRL site from the 1950’s to 2000, was used for the transportation of low-level radioactive liquid from the nuclear facilities to a licensed waste management area.  In 2019 and 2020, the majority of the pipeline was removed and pockets of contaminated soil was remediated.  
Reactor Pit 1 was a natural depression, receiving approximately 230,000 m3 of low level radioactive waste water primarily from the NRX rod and storage bays, one-off burials, and contaminated metallic debris between 1953 and the mid-1970s. Environmental characterization is currently ongoing, which will help make informed decisions on remediation in future years.
Future characterization efforts are required to model the extent of the contamination in groundwater and soil, and improve the overall conceptual site models. Utilizing a Digital Twinning technique, current data can be overlain onto a high precision, georeferenced digital model of the site.  This will allow characterization planning to accurately place borehole locations in the field with respect to both characterization gaps as well as site specific characteristics. This presentation will provide an overview of these environmental remediation projects at the CRL site.

Coauthors: Stephanie Thomson (Canadian Nuclear Laboratories)
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4:15 - 4:35 p.m.

Scene-Data Fusion Applications in the Chornobyl Exclusion Zone

Jake Hecla, UC Berkeley

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The Russian invasion of Chornobyl has generated combined radiological and explosive hazards in the Exclusion Zone. Surveys of this changed radiological environment will require novel techniques due to the combined radiation and UXO hazards present at the site. Further, the ongoing management of the New Safe Confinement structure and disassembly of the Shelter Object require responsive and versatile mapping platforms to manage emerging environmental hazards encountered during these activities. Detector platforms developed at Lawrence Berkeley National Lab (LBNL) which use a 3D radiation mapping technique known as “scene data fusion” (SDF) provide a means of rapidly mapping and locating sources of ionizing radiation in near-real-time. These advanced radiation sensing platforms employ sensor fusion methods which integrate LIDAR, camera and radiation interaction data to develop rich, three-dimensional maps of radiological environments which are easily interpreted. This method is platform-agnostic, and has been applied to UAVs, UGVs and handheld systems using multiple gamma-ray and neutron-sensing modalities. This mapping and localization capability has been previously deployed at Chornobyl, and has proven its utility to assess radiological contamination and to guide cleanup activities at a wide variety of sites. This presentation will provide an overview of the technique, the SDF platforms available and the applications of this technique at the site.

Coauthors: Kai Vetter (UC Berkeley and Lawrence Berkeley National Laboratory), Kalie Knecht (UC Berkeley)
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Open Discussion and Closing Remarks

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