Our Team

Our company represents a unique alliance of engineering/environmental consulting and geology/hydrogeophysics expertise. Many firms offering geophysical survey services do not have the necessary environmental consulting expertise that we believe is critical relative to data interpretation focused on meeting clients project objectives. Similarly, many environmental consulting firms do not have the necessary geophysical expertise that allows them to feel good about using geophysics reliably on their project sites. Aestus has over a decade of experience using these combined disciplines to help our clients solve complex problems at their project sites.

Stuart W. McDonald, P.E., President/Managing Member


Stuart McDonald (BS Civil Engineering, University of Delaware, 1990) is a licensed professional engineer (CO) with over 24 years of engineering and management experience in environmental cleanup sector. His environmental consulting background (pre-Aestus) involved cradle to grave site characterization, remedial design, remedial construction management, and operations and maintenance of remedial systems at multi-million dollar Superfund and other projects located across the United States.

Since co-founding Aestus in 2001, Stuart has worked to bring a scan first then drill approach to industries requiring ultra-high resolution subsurface characterization, with a primary focus to date on the environmental cleanup industry. He has managed GeoTrax Survey™ projects at over 175 projects across the United States and internationally and is on the forefront of helping the environmental industry develop new and improved paradigms regarding contaminant distribution and attenuation in the subsurface. Stuart has been the President of Aestus, LLC since 2006 and continues to lead the effort of developing the company to achieve its overall mission.

Todd Halihan, Ph.D., P.Gp., Chief Technical Officer


Todd-Halihan-Head-ShotDr. Todd Halihan is currently Aestus Chief Technical Officer and has been a principal with Aestus since shortly after company inception in 2001. He is also a Professor for the School of Geology at Oklahoma State University.

Todd joined Oklahoma State University in Fall 2000, after completing his Ph.D. in Geological Sciences at The University of Texas at Austin. He earned his M.S. in Geology at the University of Missouri Columbia after working as a field assistant and later director of Forfar Field Station on Andros Island, Bahamas. Todd received his B.A. in physics with honors at Monmouth College in Illinois.

Todd’s professional interests center in subsurface characterization and sustainable water supply. His expertise includes developing methods for site characterization and monitoring of contaminated sites using Electrical Resistivity Imaging (ERI) and direct push Electrical Resistance Tomography (ERT; a.k.a. cross borehole ERI). Todd’s extensive geophysical experience also includes electromagnetic, seismic and ground penetrating radar methods. His hydrogeological experience includes developing analytical models for fractured and karstic aquifers and well testing techniques.

During his collaborations with Aestus and research at OSU during 2002 and 2003, Todd was the primary inventor of the proprietary form of ERI that has subsequently been licensed exclusively to Aestus by OSU. Aestus has subsequently branded this proprietary ERI as GeoTrax Survey™.
Todd has been involved with all of Aestus 175+ projects and has also characterized numerous sites throughout the United States and also in several other countries through his ongoing university research. He is licensed as Professional Geophysicist in the State of California.

Technical, Field, and Administrative Staff

Our team also includes other well qualified and professional technical field and administrative support staff, many of whom have been with the firm for many years.