Abra J. Bentley, M.S., R.G.



Ms. Bentley, an Environmental Scientist with over 18 years of environmental experience and serving as President for Hydro Geo Chem, first began working for Hydro Geo Chem in 1991. Her project work has included management of site investigation and remediation projects; collection of landfill gas, chemical, hydrogeologic, and bioremedial system data; and preparation of interpretive reports. She specializes in water and soil chemistry as it relates to environmental problems.




-M.S. (Environmental Engineering Science) University of California, Berkeley, 1994
-B.S. (Chemistry and Biology) University of Arizona, 1991


Registered Professional Geologist, Arizona Registration No. 54327
OSHA 40-Hour Health and Safety Training for Hazardous Waste Operations, 1991
MSHA Certified Mine Safety Training

Representative Experience

Management of assessment and remediation of an MEK release at a manufacturing plant in Casa Grande, Arizona, under ADEQ's LUST program. Site characterization work included installation of wells, groundwater and soils sampling, and aquifer testing for hydraulic parameter estimation. Installation of a SVE/Thermal-Catalytic Oxidizer system for removal and treatment of explosive levels of MEK in the subsurface. Completion of an ADEQ-approved Corrective Action Plan and Site Characterization Report.  Ongoing remedial soil vapor and groundwater data collection, groundwater monitoring and reporting, including MEK removal estimation. Microcosm studies for evaluation of monitored natural attenuation and contaminant transport modeling are anticipated.

Management of a Phase III Pilot Scale Study and on-going remedial activities for cleanup of soils and groundwater impacted by LUST petroleum hydrocarbon contamination at West Sky Harbor Airport in Phoenix, Arizona. In addition to compliance with Remedial Action Objectives, project evaluated the effectiveness of bioventing, biosparging, nutrient addition, and anaerobic/aerobic cycling systems through extensive data collection, interpretation and reporting to the client and to ADEQ. Included recommendations for site-wide bioremedial technology.

Management of ongoing quarterly groundwater monitoring and reporting at West Sky Harbor Airport pursuant to ADEQ regulatory requirements. Management of ongoing vapor monitoring and reporting, and SVE oxidation system air quality monitoring and reporting pursuant to Maricopa County air quality permit requirements at the site.

Baro-pneumatic and pump tests for field air permeability and landfill gas generation measurements, plus well logging and drilling and installation oversight at a Tucson, Arizona landfill. Oversaw well lithologic logging, drilling, and well installation. Responsibilities included interpretation of soil gas analytical data, preparation of a landfill investigation report and presentation of findings to regulators. Project included deep soil vapor extraction (SVE) for protection and remediation of groundwater beneath arid landfills. SVE systems were configured to maximize removal of deep vadose zone volatile organic compounds (VOC) that had acted as a source to groundwater.

Management and execution of ongoing groundwater monitoring at a mine site in the Arizona WQARF program. Performed as part of Aquifer Protection Permit requirements under ADEQ.

Johnson and Ettinger modeling to evaluate the potential for subsurface vapor intrusion of chlorinated organics at a former manufacturing site in City of Industry, California.

Estimation of GHG emissions and evaluation of Maricopa County monitoring obligations for landfills in Arizona pursuant to 2010 EPA reporting requirements.

Estimation of landfill gas production using EPA’s LANDGEM model with appropriately chosen parameters, and waste disposal and human population data, for a closed municipal solid waste landfill in Spain.

Development and execution of a field investigation at a chemical plant that had been listed as an EPA Superfund site in Livermore, California. Performed Geoprobe soil gas and groundwater investigations, interpreted permeability and analytical data and wrote Site Cleanup Order recommendations for the client. Source areas included a UST/recycle pad.

Investigation of a deep bedrock aquifer at a mine site in Arizona. Sampled and tested new wells with a packer system and wrote up geochemical interpretation of findings. This project was part of the delineation of a very large high sulfate, high metals bearing groundwater plume within geologic formations having very different hydrologic properties.

Execution of annual field inspections, maintenance and groundwater monitoring for an engineered earthen cover designed to protect groundwater and eliminate potential surface exposure from chromium-contaminated soils in Casa Grande, Arizona. Included annual reporting based on Consent Order requirements approved by ADEQ.

Completion of a nitrate loading paper study for a developer in Kingman, Arizona. Involved interpretation of available groundwater hydrogeologic and analytical data.

Management and execution of ongoing groundwater monitoring at a mine site in the Arizona WQARF program. Performed as part of Aquifer Protection Permit requirements under ADEQ.

Perennial creek surface water investigation to evaluate the impact of an acidic mine originating groundwater plume. Included collection of surface flow and water quality data, as well as surface water samples.

Pit lake profiling studies with the collection of water samples and water quality data at various depths in a deep lake created by open-pit mining practices.

Involvement in a large-scale EPA mediation process with more than 20 sites contributing to VOC contamination in a single groundwater plume in the San Gabriel Valley, California. Evaluated sites with regard to source areas, contaminant definition and hydrogeology using site specific Information Briefs. Assisted in early cash out option comparison with client facility.

Involvement in various groundwater and soils investigations including: historic chlorinated organic spills, placement of ORC socks in wells to prevent gasoline migration, highly acidic tailings piles, carbon dioxide concerns from acidic water reacting with aquifer carbonates, and benzene migration via natural gas release.

As an analytical chemist, performed on-site analytical procedures for soil gas, groundwater, and soil investigations in mobile laboratory units using gas chromatography. Assisted with a field organic anion tracer injection, collected groundwater samples, and worked extensively with ion chromatography during a study at an EPA RCRA/CERCLA site.


UST and Water Quality Update Seminar, ENRS, State Bar of Arizona, 2004
RCRA Hazardous Waste Training, McCoy and Associates, 2004


Fischer, M.L., A.J. Bentley, et al. 1996. Factors Affecting Indoor Air Concentrations of VOCs at a Site of Subsurface Gasoline Contamination, Environ. Sci. Technol., 30, 2948-2957.

Sedlak, D.A., A.J. Bentley. 1997. The role of photochemistry in the transport and transformation of arsenic. Davis: University of California Water Resources Center, p. 13 (Technical completion report).



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