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

Registrations/Certifications

RCRA Hazardous Waste Training Seminar, McCoy and Associates, 2004
UST and Water Quality Update Seminar, ENRS, State Bar of Arizona, 2004
OSHA 40-Hour Health and Safety Training for Hazardous Waste Operations, 1991
8-Hour HAZWOPER annual refreshers
MSHA Certified Mine Safety Training

Representative Experience

• Management of a Phase III Pilot Scale Study for cleanup of soils and groundwater impacted by liquid phase petroleum hydrocarbons at an 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 interpretation of extensive field data. Work included use of tracers for sparging evaluation, porosity measurements, and mixing and movement of groundwater in the sparge zone.

• Management of ongoing quarterly groundwater monitoring pursuant to regulatory requirements under an Arizona state LUST program, as well as an ongoing quarterly vapor monitoring program. 

• 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.  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.

• Estimation of landfill gas production using EPA’s LANDGEM model with appropriately chosen parameters for a closed municipal solid waste landfill in Spain. 

• Development and execution of a field investigation at a chemical plant in Livermore, California. Performed Geoprobe soil gas and groundwater investigations. Interpreted permeability and analytical data and wrote Site Cleanup Order recommendations for client.

• 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 of an engineered earthen cover designed to protect groundwater and eliminate potential surface exposure from chromium-contaminated soils.

• 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. Included scheduling, oversight, and large volume data collection and manipulation.

• 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.

• Large scale EPA mediation process involving more than 20 sites contributing to a single groundwater plume. 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.

• Various groundwater and soils investigations including: projects related to UST leaks, 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.

PROFESSIONAL PUBLICATIONS:

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

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