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Elisabeth Hawley
Elisabeth Hawley

Senior Consultant
Geosyntec Consultants

Elisabeth L. Hawley, P.E. (CA) is a Senior Consultant at Geosyntec Consultants, Inc. with 17 years of experience advancing environmental remediation projects involving site characterization, fate and transport, remediation, strategies to achieve site closure, and litigation support services. Her area of expertise include per- and polyfluoroalkyl substances (PFAS) and other contaminants of emerging concern. PFAS projects have included design and implementation of site investigation work plans, preparation of field sampling protocols, assessment of PFAS sources and fate and transport, and development of innovative treatment technologies. She is the co-chair of Geosyntec's PFAS practice group.

Workshop Presentation

Assessing and Mitigating Bias in PFAS Concentration during Groundwater and Surface Water Sampling

Assessing and Mitigating Bias in PFAS Concentration during Groundwater and Surface Water Sampling

Dr. Jennifer A. Field1, Trever Schwichtenberg1, Dr. Dorin Bogdan2, Dr. Charles E. Shaefer, Jr.3, Bill DiGuiseppi4, Amanda Struse4, Heather Rectenwald4, Elisabeth L. Hawley5, and Dr. Rula A. Deeb5

Oregon State University, 2AECOM, 3CDM Smith, Inc., 4Jacobs, 5Geosyntec Consultants, Inc.

Topics: Per- and Polyfluoroalkyl Substances (PFAS); Advances in Site Characterization Tools and Approaches

Abstract: This workshop will provide participants with science-based recommendations to minimize sampling bias during per- and polyfluoroalkyl substances (PFAS) sampling, while reducing unnecessary costs and efforts associated with overlay conservative sampling recommendations or procedures. An examination of potential bias was motivated by widespread assumptions that PFAS can be introduced during or after sample collection, as well as PFAS transformation in the laboratory during sample storage, even when standard field procedures are followed. The workshop will summarize the scientific state of knowledge regarding potential for bias in PFAS sampling, present findings of new research conducted, and provide scientifically based guidelines for practical field sampling equipment and procedures to minimize the potential for bias. Research to evaluate bias in techniques for surface water PFAS sampling will be presented, including a method for surface microlayer (SML) to assess PFAS stratification and enrichment at the air/water interface and variability in field measurements using different common PFAS sampling methods. 

Learning Objectives:

1. Similarities and differences among state and Federal guidelines for PFAS field sampling practices 

2. Scientifically based or conservative? Basis for PFAS sampling guidelines and recommendations to improve the current state of practice.

3. Effect of sampling techniques, sample storage temperature, and hold time on PFAS concentrations in groundwater and/or surface water.

4. Evaluation of PFAS surface water sampling techniques and if impacted by inclusion of the SML.