Use of chemical fingerprint data to enhance remedial site investigations at petroleum impacted sites

ABSTRACT As well known by remediation practitioners, the indispensable “road map” for remedial site investigation is the conceptual site model (CSM), in which contaminant sources and migration pathways are two of the most critical CSM components. The ultimate goal of site investigation is to delineate the extent of contaminants, which is constrained by migration pathways. As contaminant sources are the starting points of the migration pathways, understanding contaminant sources is critically important in developing and refining a CSM. In the world of liability dispute and litigation, identification of sources of petroleum hydrocarbons is one of the, if not the only, objectives. A variety of environmental forensic techniques have been developed over a long history of litigation and the validity of these techniques has been established through publication in peer-reviewed scientific journals and books, as well as the vigorous scrutiny of the litigation process. Among the techniques, chemical fingerprinting is arguably the earliest developed and the most widely used technique for petroleum hydrocarbon forensics. During remedial investigations at complex petroleum impacted sites, chemical fingerprint data are equally of value for source identification, which in turn helps in development and/or enhancement of CSMs. This article presents an overview of applications of chemical fingerprinting in remedial site investigation at petroleum hydrocarbon-impacted sites. The first scenario is about avoiding unnecessary site investigations through proving nonexistence of perceived or suspected contaminant sources. The second scenario is about mapping out light nonaqueous-phase liquids (LNAPL) migration pathways using petroleum biomarkers. The third scenario is about expediting cleanup by differentiating current from historical releases using GC/FID chromatograms. The final scenario is about application of chemical fingerprinting in natural source-zone depletion evaluation. Common to all the applications is that there is no involvement of other potential responsible parties. The chemical fingerprinting techniques were used to achieve the goals of remedial investigations through effective site characterization. In all scenarios, the effective site characterization helped to avoid unnecessary remedial investigation and/or to realize considerable cost savings when remediation is implemented.