Dawn Zemo

Dawn A. Zemo received her M.S. in geology from Vanderbilt University in 1982. She started her career in the oil industry in Houston and then practiced in the field of environmental site investigation and remediation from 1988 to 2022. Ms. Zemo worked at Ecology & Environment, Geomatrix Consultants (SF Bay Area), and in 2002 formed Zemo & Associates, from which she retired in 2022.  She was a Professional Geologist and a Certified Engineering Geologist in California. Dawn’s achievements in the environmental field focused on identifying technical problems that broadly negatively impacted data collection and/or interpretation at typical sites and then developing or championing defensible ways to improve both to advance our practice. She thanks her many colleagues and collaborators who helped her wrestle with these issues over the years.  Dawn was an early adopter and educator (e.g., giving presentations and workshops, author of peer-reviewed publications) in the following areas: Use and validity of groundwater screening methods at chlorinated solvent (CVOC) and petroleum hydrocarbon (PH) sites using CPT/Geoprobe/Hydropunch, (1990-1995); The imprecision of the TPH analysis (Method 8015, etc.) in soil and groundwater samples (1992-); Use of “forensic chemistry” approaches (e.g., TPH Chromatograms and PAH data, etc.) in routine site work and litigation (1994-); Problems with groundwater data at PH sites from (a) non-dissolved hydrocarbons (HCs) (turbid samples collected from within the smear zone) (1996-), and (b) dissolved non-HCs (natural organics, biodegradation products, CVOCs, etc.) being quantified as TPH (1994-). She championed a gravity-settling protocol to isolate the dissolved fraction in samples, and also a column-based silica gel cleanup protocol used to separate polar and non-polar fractions prior to TPH analysis. From 2011 through 2022, Dawn was part of an applied research team studying the nature and toxicity of dissolved non-HCs in groundwater at biodegrading fuel and crude oil release sites that are measured as “TPH” unless a SGC is used prior to sample extraction, using research-level analytical methods (initially GCxGC-MS and later also HRMS) and whole-groundwater toxicity testing. Between 2012 and 2022, Dawn presented this work in more than 50 platform presentations and technical/regulatory workshops/seminars and co-authored 12 peer-reviewed publications (9 for fuel sites and 3 for the Bemidji crude oil site).  In a 2022 White Paper, Dawn recommended a practical approach for regulatory agencies to use these results to set drinking-water screening levels for the non-HC mixture at typical PH release sites.

 
Dawn served on the editorial review boards/peer review teams for the international journals Ground Water Monitoring & Remediation and Environmental Forensics, and on the AEHS West Coast Conference Scientific Advisory Board for almost 2 decades. Over her career, Dawn’s expertise was sought by multiple State and National regulatory agencies, and other groups, in helping develop RBCA guidance and/or TPH guidance. She was the technical expert author for 3 Chapters of the 2012 “Leaking Underground Fuel Tank (LUFT) Manual” guidance document (Fate and Transport; Site Assessment; Laboratory Analysis), and also served as a technical expert consultant during development of the 2012 “Low-Threat UST Case Closure Policy”, both on behalf of the California State Water Resources Control Board UST Program.  

Dawn is currently enjoying retirement in Reno, Nevada.