// Frequently Asked Questions

Data Quality in Brackish/Saline Environment

Can Aestus Image Successfully in a Brackish/Saline Environment?

YES

Aestus’ GeoTrax Survey™ specialty ERI methods CAN detect electrically resistive anomalies within a conductive environment such as brackish/saline groundwater and with good data quality
This is contrary to the use of standard electrical resistivity imaging (ERI) techniques which have difficulty imaging or “seeing” resistive targets of interest (e.g., contamination which sometimes has an electrically resistive signal) in a highly conductive environment
Aestus’ methods allow pockets of contamination to be detected, even in brackish/saline environments, to achieve more certainty of subsurface conditions
Other electrical resistive targets (e.g., gravel channels) can also be detected in an electrically conductive matrix.

Real-life example at a site with chlorinated solvent and petroleum hydrocarbon impacts:

The site’s groundwater is brackish/saline due to the influence of nearby bodies of water
Aestus’ GeoTrax Survey™ successfully generated a drillable image and identified electrically resistive zones, despite a low background electrical resistivity (i.e. high conductivity) of 3 Ω-m or less
The electrical resistive anomaly was drilled and confirmed to be impacted with TCE (and its daughter products), and petroleum hydrocarbons over regulatory standards in groundwater

GeoTrax Survey™ image of brackish site showing targeted and untargeted drilling locations

How does Aestus see electrical resistors in a highly conductive matrix?

Aestus’ proprietary method of data collection and processing (GeoTrax Survey™) is up to several orders of magnitude more sensitive than traditional methods (Miller et al., 2014), ensuring the resulting images are more representative of the subsurface. ERI data are collected as raw resistivity data that have to be inverted (i.e., processed) to produce a model of the resistivity structure of the subsurface. The sensitivity refers to how well the inversion can detect spatial variability of resistivity. Greater sensitivity yields higher image accuracy relative to representing subsurface conditions, which leads to a more “drillable” image.

Below is a sensitivity plot comparison of Aestus’ GeoTrax Survey™ versus a standard ERI survey collected at the same location using the same electrode configuration and equipment. Green zones denote high sensitivity (i.e., high certainty); yellows are zones with lower sensitivity but, with proper QA/QC, can still be used to target drilling locations; red are zones with extremely low sensitivity/certainty that indicate very little constraint on the inversion (i.e., should not be used to target drilling locations). Note that most of the standard ERI sensitivity plot is either red (indicating the image would not be targetable) or is blank at depth (i.e. NO data remained after inversion due to high noise and inherent limitations of the standard ERI approach).

Diagram comparing GeoTrax Survey Protocols to Standard ERI Protocols

Download PDF

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.

Madison Culver, M.Sc.

Staff Geologist / Field Technician

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.

Stuart is based out of Loveland, Colorado.