Environmental Forensics
Environmental forensics has increasingly played a key role in settling insurance coverage claims and identifying responsible parties.
While it should always be the aim of the environmental consultant to construct a site conceptual model for the source, fate and transport of contaminants in the environment, the analytical methods practiced in environmental forensics add a degree of certainty by establishing multiple, corroborating lines of evidence.
The science of environmental forensics is ever-evolving. The following list includes analytical tools at the consultant’s disposal-- some routinely applied and widely accepted in the industry:
Establish Operational History: A thorough knowledge of a site’s operational history is a necessary first step in identifying the possible timing, source and composition of a release. It is important to research raw material use, heating and fuel sources, and common waste disposal and housekeeping practices during each tenancy.
Fingerprinting: Indicator parameters, such as the gasoline additives MTBE, ethanol and lead, are used to identify the source product. These parameters often serve as the first line of evidence in establishing the timeframe for a release. They are also useful in the identification of separate release events and distinct contaminant plumes. This is true because the phase-in and phase-out periods for these compounds are well defined.
Hydrology: Groundwater flow rate, along with the extent of the contaminant plume, is used to determine elapsed time from the release event. In addition, the groundwater flow direction is calculated to help identify the most likely source of a release from a number of possible sources. The flow direction is often more difficult to establish correctly in a heterogeneous environment, due to directional hydraulic conductivity values. However, most consultants do not take this into account and rely on the groundwater flow direction established by groundwater elevation contours. Additional data generated from slug tests and extended pumping tests may be needed to definitively determine the groundwater flow direction.
Isotopes: Certain istotopes serve as markers in time in human history. These isotopes enter groundwater via the hydrologic cycle. For example, the detonation of hydrogen bombs at the end of World War II spread tritium throughout the atmosphere worldwide. Tritium is found at certain depths in groundwater across the globe.
Weathering: Contaminants undergo the process of weathering as soon as they are released to the environment. Weathering processes include microbial biodegradation, mechanical dissolution and chemical breakdown. Moisture, clay content, oxygen levels, pH and many other factors affect the rate of weathering.
The relative state of weathering can be determined by laboratory analysis, including gas chromatography. A gas chromatograph of a laboratory standard is compared to that of a weathered product in the subsurface.
Dendroecology: Plants uptake contaminants in soil and groundwater. In the case of trees, the presence of contaminants in annual rings can provide evidence of the time that the contaminants first appeared in the environment.
