Dr. Tamzen W. Macbeth

Advances in High-Resolution Site Characterization Technologies and Applications for PFAS  

Dr. Tamzen W. Macbeth, Ph.D, PE, BCEE, Senior Vice President and Remediation Practice Leader, 

CDM Smith, Inc.

Complex contaminated soil, sediment and groundwater sites are difficult to restore and require robust conceptual site models (CSMs) that represent site complexity with sufficient detail and at appropriate scales to support more effective remedy decision-making. AFCEC published a guidance document and tools selection table on over 60 high resolution site characterization tools (HRSCs) to support improved CSMs and decision-making throughout a remedy life cycle. The 60 HRSC technologies were compiled and grouped according to the types of data they generate including physical (i.e., geology hydrology), chemical (i.e., phase, composition and properties of contaminant, biogeochemical aquifer properties), and attenuation (i.e., sorption, biotic and abiotic degradation).  The HRSC technologies were also grouped based on the information they provided, i.e., screening level (e.g., geophysics tools or membrane interface probe), semi-quantitative (e.g., cross- hole tomography), and quantitative (e.g., flux meters or porewater rock coring evaluation).    PFAS characterization requires a unique understanding of both the characteristics if these chemicals and the physical, chemical, biogeochemical and attenuation properties of the environment. In this presentation we will focus on how to use high-resolution tools to support evaluations of PFAS leaching from vadose zones in soil and sediment to groundwater. Our current state of science has elucidated critical parameters to understand sorption and desorption properties (particularly with respect to the air-water interfacial sorption which is unique to PFAS compared to other contaminants), partitioning in co-contaminants such as petroleum hydrocarbon light nonaqueous phase liquids (LNAPL) or chlorinated solvent dense nonaqueous phase liquids (DNAPL), partitioning into percolating porewater and the role of PFAS precursors as future sources of toxic PFAAs. We will discuss the tools and methods which can fill these data gaps to develop a better CSM to quantify PFAS leaching for remedial decision-making.  

Dr. Tamzen Macbeth is Senior Vice President and Remediation Practice Leader for CDM Smith with over 20 years of experience in cleanup of hazardous waste contaminated sites.  Her work leverages her interdisciplinary academic and research background in microbiology and engineering to advance remediation technologies to clean up non-aqueous phase liquids (NAPLs), dissolved organic, inorganic, radioactive chemicals and emerging contaminants, such as PFAS, under a variety of regulatory programs. She has served as principal investigator, manager and/or technical lead and advisor for government, private and international contaminated sites undergoing characterization, design, and remediation at the laboratory-scale, pilot-scale and full-scale. Dr. Macbeth has published more than 100 technical papers, presentations, training manuals and guidance documents on remediation topics, and seminars and short courses for the ITRC, USACE, Navy RITS, and been an invited speaker at international conferences and symposia on remedial technology application for cost-effective cleanup. She is also an affiliate faculty member at Idaho State University.