Temporal Electrical Monitoring of Remedial Injections
Project Challenge/Solution:
An estimated 23 billion gallons of groundwater beneath a former ordinance plant in Nebraska was contaminated with RDX and TCE above regulatory standards. Remedial efforts originally included an extensive and costly pump-and-treat system to manage the plume. Projections estimated this system would need to operate for more than 125 years.
In need of a more effective remedial strategy, ESTCP funded a pilot-scale ISCO injection demonstration. When twelve downgradient wells and eight direct push profiles could not provide enough data to quantify the distribution of permanganate within the aquifer material, Temporal Electrical Resistivity Imaging (TERI) was utilized to monitor the injectate movement by imaging the subsurface before, during, and after injection.
TERI works like standard (static) ERI; however, rather than producing a single snapshot of the subsurface, it characterizes the electrical changes that occur between different imaging events. This methodology is ideally suited to tracking injected materials as any injectate will have different electrical properties than native materials. A high-sensitivity version of the technology demonstrated injection tracking to 100 ft bgs (30 m) for this pilot scale project. This enhanced capability is commercialy available as Aestus GeoTrax Monitoring™.
The graphic above shows how a TERI line (yellow) for this investigation was oriented in conjunction with the permanganate injection plane (green).
ESTCP Report: Comfort, S., Halihan, T., and V. Zlotnik, 2009, Using Electrical Resistivity Imaging to Evaluate Permanganate Performance during an In Situ Treatment of an RDX-Contaminated Aquifer, ESTCP Report, US DoD, 129 p.
Delineation of ISCO Injection:
The graphic below shows the TERI transect perpendicular to the injection plane that tracked subsurface changes around an extraction well, EW-01, and a system of monitoring wells. The vertical green line indicates the orientation of the injection plane, and the vertical dark grey lines are monitoring well locations. The TERI data show what changed from pre-injection to post-injection: the purple and blue anomaly represents a decrease in electrical resistivity (i.e., an increase in electrical conductivity), which is interpreted to be the permanganate injection as it migrated from the injection wells.
TERI images revealed that the permanganate was not creating a uniform curtain of injectate as intended but followed preferential flowpaths and migrated below several monitoring well screens, and (in some cases) even flowed against the regional groundwater gradient. Unexpectedly, the images also showed that a large amount of permanganate squirted upwards into the vadose zone rather than staying below the water table (note that the bulk of the purple anomaly is above the water table).
TERI provided predictive insight, which was validated by monitoring well sampling:
Imaging indicated that the injectate plume would intersect the screened interval; groundwater sampling from MW-13 confirmed the presence of permanganate within the well
Imaging showed the injectate plume had migrated below the screened interval; permanganate was not detected in groundwater samples collected from MW-03.
Injectate Monitoring using Temporal Electrical Resistivity Imaging (TERI):
Injected materials rarely behave as expected and often follow flowpaths that are not known in advance, especially without continuous imaging. The temporal imaging and well sampling suggested that the monitoring well network was not well suited to track injectate flow across the site as the wells could not delineate the flowpaths controlling the bulk of the permanganate distribution. TERI, however, is particularly well suited to informing the radius of influence for injection events and successfully highlighted the subsurface preferential flowpaths controlling the injectate migration at this site.
Published study available as Halihan, T., et. al., 2011, Electrical Resistivity Imaging of a Permanganate Injection During In Situ Treatment of RDX-Contaminated Groundwater: Groundwater Monitoring & Remediation (https://doi.org/10.1111/j.1745-6592.2011.01361.x)
Results
Injected materials rarely behave as expected and often follow preferential flowpaths that are not known in advance when informed only by monitoring wells/borings
A network of monitoring wells was unable to adequately track a permanganate injection across an impacted site
Mapping spatial distribution of in-situ injections was possible using Temporal Electrical Resistivity Imaging (TERI)
See below. Succeed above.
When clients need more certainty in their subsurface data, GeoTrax Monitoring™ electrical images integrated with existing site data and confirmation drilling data yield a more complete understanding of the subsurface, allowing them to:
Guesswork is the enemy of smart drilling. It leads to wasted money, rework, and nonstop frustration. Aestus scans your site and interprets the data so you can see what’s beneath the surface, make smart decisions, and keep your project moving forward.
Since joining Aestus in 2024, Madison has performed various project tasks including field data acquisition, data integration and analysis, 2D and 3D visualization, and project report development.
As an undergraduate at Oklahoma Sate University, Madison utilized electrical resistivity imaging to locate a drilling target for a municipal water well in rural Oklahoma. Her Master’s degree, also from Oklahoma State University, focused on the production and laboratory testing of a novel groundwater tracing particle for use in a sole source aquifer.
Madison previously worked at an environmental consulting firm in Dallas, Texas, where she performed soil/groundwater investigations/reporting, PFAS sampling programs, and Environmental Site Assessments.
Madison is based out of Irving, Texas.
Michelle Lahti, PACE
Administrative Director
Since joining Aestus in 2021, Michelle has supported the CEO and other managers in their day-to-day needs. She also manages human resources and all elements of the many conferences Aestus attends. Michelle works hard to ensure that the needs of stakeholders are addressed in all steps of the business process when working with our clients. Michelle has a bachelor’s degree in Avionics Engineering Technology from Embry-Riddle Aeronautical University. She also has experience as a small business owner, and over 15 years’ experience as an executive assistant in many different industries. She has her Professional Administrative Certification of Excellence (PACE) through the American Society of Administrative Professionals (ASAP). Michelle is based out of Wellington, Colorado.
Autumn M. Town, M.Sc.
Staff Geologist / Field Technician
Autumn performs various project tasks for Aestus, including field data acquisition, data integration and analysis, 2D and 3D visualization, and project report development. Since joining Aestus in 2023, she has helped meet project objectives such as mapping stratigraphy, identifying areas of contamination, and characterizing preferential flow pathways at complex sites across the United States. As an undergraduate at Oklahoma State University, Autumn utilized electrical resistivity imaging (ERI) to evaluate the hydrogeologic effects of PFAS-containing firefighting foams. While completing her Master’s degree, also at Oklahoma State University, she focused primarily on sedimentology and stratigraphy as she studied the effects of depositional and diagenetic processes on porosity development in a tight gas sandstone reservoir.
Autumn is based out of Tulsa, Oklahoma.
Morgan Love, M.Sc.
Senior Project Geologist
Morgan has been a part of the Aestus team since 2012. She supports all aspects of data integration for Aestus in 2D and 3D space, including modeling of geophysical, geochemical, and geologic data. She also performs geophysical data processing and develops quality control and automation protocols to ensure data integrity.
Prior to Aestus, Morgan used her environmental geology undergraduate degree working for a water resource company, a geosciences software company, and a seismic data acquisition company. She holds a Master's Degree in Computer Information Systems.
Morgan is based out of Fort Collins, Colorado.
Grant Eastman
Equipment Manager / Field Technician
Grant maintains all our equipment and vehicles at a firehouse ready status in order for the field team to be ready to mobilize at moment’s notice. He also troubleshoots any technical issues that come up as well as being a member of the field team.
Grant graduated from Colorado State University with a degree in Watershed Science. After graduating he completed 8 years of military service with the Colorado Army National Guard, including two deployments to the middle east. Before joining Aestus, he was a senior technician building custom automation equipment and wire harness mockups for aerospace companies.
Grant is based out of Milliken, Colorado.
Samantha Frandsen, M.Sc, P.Gp.
Hydrogeophysicist / Project Manager
Since joining Aestus in 2018, Samantha has performed all aspects of the Aestus project lifecycle, including acquisition field work, processing of geophysical data, data integration, 3D visualization, and reporting. As project manager, she oversees a variety of projects completed at complex sites across the United States and strives to help our clients efficiently leverage Aestus’ high-resolution GeoTrax Survey™ data to improve understanding of subsurface conditions.
Prior to her time with Aestus, she earned her Bachelor’s degree (magna cum laude) in Physics from the University of Richmond and taught high school physics as a Teach for America corps member. She then completed her Master’s degree (Distinction) in Exploration Geophysics at the University of Leeds in the UK. For her thesis, she utilized several different geophysical techniques to characterize the subsurface remains of a former gasworks facility for which she was awarded the GETECH award for best overall performance in the Independent Project and the Association for Industrial Archaeology’s Dissertation Award.
When she’s not investigating what’s below the ground, Samantha enjoys exploring all the above-ground fun her Stateline (South Lake Tahoe), NV home has to offer via trail running, mountain biking, and snowboarding.
Samantha is based out of Stateline, Nevada.
Michael McNair
Project Geologist / Field Team Leader
Michael has worked on a variety of project types using Aestus’ electrical hydrogeology techniques to help Aestus’ clients succeed relative to characterization of contaminated sites, evaluating geohazards, municipal water well exploration, and monitoring subsurface changes over time. Michael currently manages Aestus’ field operations to collect high quality subsurface electrical imagery (GeoTrax Survey™) at rural, urban, and industrial sites with complex logistics. When not in the field, Michael is a key member of Aestus’ reporting team and leads or assists with 2D/3D data integration, QC, data interpretation, and reporting.
Michael previously worked at an environmental consulting firm in Dallas, Texas, where he performed soil/groundwater investigations in the field and subsequently developed reports. Michael earned a Bachelor of Science in Geology from Baylor University.
Michael is based out of Orlando, Florida.
Todd Halihan, Ph.D., P.Gp.
CTO/Data Interpretation Lead
Todd’s focus at Aestus centers on subsurface characterization using electrical hydrogeology and sustainable water supply. He is also a professor and the Sun Company Clyde Wheeler Chair in Hydrogeology at Oklahoma State University. He was the National Ground Water Association’s 2018 McEllhiney Lecturer and he is a founding member of the NGWAU program for groundwater outreach and education.
Dr. Halihan is the recipient of the American Institute of Hydrology’s C.V. Theis Award winner. He is also a professional geophysicist (CA), professional driller (OK) and a PADI divemaster.
Todd is based out of Stillwater, Oklahoma.
Stuart W. McDonald, P.E.
CEO/Project Executive/Contracting
Stuart has dedicated over 20 years of his career overseeing the development of Aestus with the goal of empowering clients worldwide to gain more certainty in subsurface issues to make better technical decisions and save time and money on their projects. He has been involved in managing hundreds of projects for Aestus in the USA, Europe, Asia, and South America.
Stuart spent the first decade of his career as an environmental consultant primarily with Canonie Environmental and Harding Lawson Associates and gained experience performing cradle to grave site characterization and remediation work on high profile Superfund and other projects. This experience was the genesis of founding Aestus in 2001 as it became clear that the environmental industry needed more data density and more certainty for optimal decision-making on projects.
