Supporting Liability Arguments with Environmental Forensics

Copy of Copy of Forensics Blog Post SES

The evaluation of a contaminated site under both the state and federal regulatory frameworks involves sample collection, laboratory analysis, and comparison of results against relevant criteria. Remediation is required for areas of the site that exceed these criteria. This process is costly, often resulting in mediation over the allocation of remedial costs or litigation related to cost recovery. Strong liability arguments are needed to define and support your (or your client’s) share of costs. Environmental forensic methods are a powerful tool that can be used to support these arguments.

Environmental Forensic Methods

Environmental forensics is a blanket term used for a wide variety of statistical methods conducted with the intent of differentiating sources of environmental contamination. These methods can be used to help reveal the potential sources (and likely parties) responsible for contamination at your site. Examples of these forensic techniques include:

  • Chromatogram Fingerprinting: The organic compounds present in petroleum products can be vaporized and separated using gas chromatography. The most volatile compounds are detected first, followed by the less volatile constituents. The pattern of compounds detected in a sample is a chromatogram, which serves as a fingerprint that can be used to differentiate various petroleum products, distillates including diesel and fuel oils, as well as the degree of weathering. These techniques are primarily qualitative in nature and can be used to distinguish hydrocarbons in co-mingled plumes and to determine the age of a hydrocarbon plume via weathering products. Figure 1 is an example of chromatograms associated with gasoline and diesel, highlighting the differing hydrocarbon constituents of these two fuels.
  • Alkylated PAH Analysis: Polycyclic aromatic hydrocarbon (PAH) contamination is a common element of upland and sediment sites. Regulatory agencies rely on the analysis of a narrow subset of PAH compounds for criteria comparisons. The analysis of additional alkylated PAH compounds can help to determine the source material as alkylated PAH are more common in petroleum (petrogenic) based sources and less prevalent in combustion (pyrogenic) based sources. In addition, ratios of PAH compound pairs can serve as diagnostic indicators to aid in differentiating common PAH containing materials like creosote, manufactured gas plant tars, and urban background-based contamination.
  • Chemometric Methods:  Chemometric analysis is a statistical approach to the interpretation of patterns in complex data sets (pattern recognition). Chemometric methods include commonly referenced techniques like principal components analysis (PCA) but also more comprehensive unmixing models that can be used to qualitatively identify unique chemical signatures present in a data set and to quantify the amount these signatures contribute to each sample. Chemometric methods can be applied to any chemical data but are commonly used with polychlorinated biphenyl congeners (PCBs) and dioxin/furan congeners.

SoundEarth Strategies and the Use of Forensic Methods

As noted, regulatory guidance is intended to define and delineate the extent of remediation. It is not intended to help determine liability. As a result, data collected under the remedial investigation process is often insufficient for analysis using the above techniques. Dr. Hafner and Mr. Cammarata have successfully used forensic methods at a variety of sites. In addition, they have experience preparing effective study designs that meet regulatory requirements while also achieving the data quality objectives required for forensic analysis. Planning ahead in this manner can avoid the significant expense of resampling.

Forensic methods are a powerful tool for getting more out of your chemical data. Findings from these methods should always be supplemented with thorough historical research of your site. Connecting a chemical source signature identified via forensics with historical records of product usage provides an additional line of evidence. Please contact Dr. Hafner or Mr. Cammarata to discuss how we can support a forensic and historical investigation of your contaminated site.

Figure 1. Chromatographic “fingerprint” for a) gasoline and b) diesel range hydrocarbons.