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Gary Thomas, P.G.

Mr. Thomas is a professional geologist in California with over 19 years of experience in site investigations, hazardous waste remediation, regulatory compliance, and project management. Before joining PES in 2006, his experience was gained as a geologist at both nationwide and small consulting firms. Mr. Thomas has developed specialized expertise in managing and conducting Phase I and II environmental site assessments of residential, commercial, and industrial sites, development of site investigation work plans, monitoring well design and installation, remedial action planning and implementation, waste management, cost analysis, and report preparation.

Representative projects summarizing Mr. Thomas’ experience include the following:

  • Project Manager for a field program that involved collecting soil and groundwater samples at an active industrial facility in Napa, California. With oversight by the San Francisco Regional Water Quality Control Board (RWQCB), extensive additional sampling was performed at various locations throughout the facility to supplement existing data. In total, over 1,600 chemical tests were performed on soil and groundwater samples collected, including analysis for petroleum hydrocarbons, volatile organic compounds (VOCs), metals, and pH. Also assisted in preparing large portions of a five volume remedial investigation, feasibility study and remedial action plan report (RI/FS/RAP) for the facility;
  • Task Manager for a soil remediation project at an active bulk-storage tank farm. Approximately 410 cubic yards of soil were removed using jackhammers and manual tools during excavation activities at the site. Excavation depths ranged from 6 inches to 4 feet below ground surface (bgs). Soil confirmation sample were collected to assess the whether site total petroleum hydrocarbon exceeded cleanup levels established by the RWQCB;
  • Project Manager for a field program that involved the installation of over 100 injection points that were used to inject a dilute carbohydrate solution into multiple water-bearing zones. The injected solution created an in-situ reactive zone (IRZ) for the remediation of VOC-affected groundwater. The field program also involved the installation and sampling of wells to monitor the effectiveness of the remedial program. Extensive subsurface geologic characterization was necessary to assess water-bearing zones locations and to understand the fate and transport of contamination;
  • Field Manager for the installation of groundwater extraction, recovery, and monitoring wells in multiple water-bearing zones for a groundwater treatment system (combined liquid-phase granular activated carbon [LPGAC] and air stripping) at a Former Bulk Fueling Facility in Dinuba, California; and
  • Conducted various Phase I environmental site assessments for property buyers, sellers, developers, and lenders. Properties have included residential, commercial, and industrial properties in conformance with specific lender requirements and American Society for Testing and Materials guidelines.


Daniel A. Balbiani, P.E.
Robert S. Creps, P.E.
James P. Dunn, P.G.
Kyle S. Flory, P.G.
Susan E. Gahry, P.E.
William W. Mast, P.G.
Carl J. Michelsen, P.G., C.HG.
Keith O’Brien, P.G., C.HG.
Nicholas C. Pogoncheff, P.G.


Peter D. Gorman, C.HG.
William Haldeman, L.G.
Kris McCormick, CAC, REA
Brian O’Neal, P.E.
Chris J. Baldassari, P.G.
Scott Morrison, P.E.
Gary Thomas, P.G.
Mark Winters, R.G.

Senior Personnel

Matthew Dahl, P.E.
John Alexander
Justin Patterson

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