Principals

Gradient's Principals are nationally recognized experts and active contributors to the promotion of sound science. We maintain our position as leaders in our scientific specialties through professional certifications, peer-recognized publishing, panel and conference participation, continuing education, and hands-on work on some of the world's most challenging environmental issues.

Barbara D. Beck, Ph.D., DABT, FATS

Principal

Expertise

  • Inhalation Toxicology
  • Metals Toxicology
  • Historical Understanding of Toxicology
  • Regulatory Comment
  • Risk Communication

Andrew B. Bittner, M.Eng., P.E.

Principal Scientist

Expertise

  • NAPL Transport
  • Groundwater & Surface Water Modeling
  • Groundwater Hydrology
  • Soil Vapor Intrusion Modeling
  • Hydraulic/WWTP Modeling

Teresa S. Bowers, Ph.D.

President

Expertise

  • Statistical Methods
  • Geochemical Modeling
  • Exposure Modeling
  • Blood Lead Modeling
  • Lead, Arsenic, & PCBs
  • Cleanup Levels
  • Risk Communication

Catherine Petito Boyce, S.M.

Principal Scientist

Expertise

  • Exposure Modeling
  • Toxicity Assessment
  • Regulatory Comment
  • Cleanup Negotiations
  • Probabilistic Methods
  • Risk Assessment

Eric L. Butler, Ph.D.

Principal

Expertise

  • Environmental Forensics
  • Chemical Fingerprinting
  • Analytical Methods
  • Source Allocation
  • TPH, PAH, PCBs, Dioxins, Solvents, & Metals
  • Contemporary Archeology

Samuel A. Flewelling, Ph.D.

Principal Scientist

Expertise

  • Hydrological Modeling
  • Chlorinated Solvents
  • NAPL
  • Metals
  • Soil Vapor Intrusion

Julie E. Goodman, Ph.D., DABT, ACE, ATS

Principal

Expertise

  • Epidemiology
  • Toxicology
  • Risk Assessment
  • Product Safety
  • Carcinogenesis

Kurt Herman, M.Eng., P.G.

Principal Scientist

Expertise

  • Contaminant Fate & Transport
  • Environmental Forensics
  • Cost/Liability Estimation
  • Historical Operations & Waste Practices

David E. Langseth, Sc.D, P.E., D.WRE

Principal

Expertise

  • Surface & Groundwater Hydrology
  • Water Quality Evaluation
  • Environmental Liability Evaluation

Thomas A. Lewandowski, Ph.D., DABT

Principal Scientist

Expertise

  • Metals Toxicology
  • Pharmacokinetic Modeling
  • Reproductive & Developmental Toxicology
  • Risk Assessment

Ari S. Lewis, M.S.

Principal Scientist

Expertise

  • Metals Toxicology
  • Molecular Toxicology
  • Human Health Risk Assessment
  • Arsenic Toxicology

Christopher M. Long, Sc.D., DABT

Principal Scientist

Expertise

  • Indoor/Outdoor Air Pollution
  • Air Sampling, Measurement, & Modeling
  • Exposure Assessment
  • Inhalation Risk Assessment

David E. Merrill, M.S.

Principal

Expertise

  • Risk-based Cleanup Negotiations
  • PCBs & Sediments
  • Multimedia Modeling
  • Statistical & Monte Carlo Methods
  • Database Design & Synthesis

Lorenz R. Rhomberg, Ph.D., FATS

Principal

Expertise

  • Weighing Toxicologic Evidence
  • Quantitative Risk Methods
  • Pharmacokinetic Modeling
  • Chlorinated Solvents
  • Risk Policy & Methodology
  • Cumulative Risk

Manu Sharma, M.S., P.E.

Principal

Expertise

  • Contaminant Fate & Transport
  • Environmental Forensics
  • Pharmaceuticals in the Environment
  • Hydraulic Fracturing
  • Risk-based Remediation
  • Chemical Registrations
  • Cost Allocation/Liability Assessment

Peter A. Valberg, Ph.D., FATS

Principal

Expertise

  • Risk Communication
  • Inhalation Toxicology
  • Exposure Modeling
  • Airborne Pollutants & Particulates
  • Radiation & Radionuclide Risk
  • Electromagnetic Fields

Tim Verslycke, Ph.D.

Principal Scientist

Expertise

  • Molecular & Environmental Toxicology
  • Standard & Regulatory Chemical Screening & Testing
  • Pharmaceuticals in the Environment

A. Dallas Wait, Ph.D.

Principal

Expertise

  • Consumer Product Characterization
  • Natural Product Chemistry
  • Environmental Chemistry & Forensics
  • Test Method Evaluation & Design
  • Historical Analytical Chemistry Practices
  • Data Quality