Search

Perchlorate (ClO4 −) is an emerging contaminant whose presence and origin is of considerable environmental interest. This article discusses known sources of perchlorate and available forensic techniques to distinguish between naturally occurring and anthropogenic origins. Forensic techniques presented include stable isotopic analysis (37Cl/35Cl, 87Sr/86Sr, 16O/17O), surrogates analysis (nitrates, sodium, chlorides, phosphate, nitroglycerins, metals, strontium), historical information assessment (aerial photography, propellant use and chemistry, firing range usage), geologic analysis (limestone, caliche, playa crusts, hanksite [Na22K(SO4)9 (CO3)2Cl], potash, phosphate ore, etc.), x-ray diffraction (XRD), and scanning electron microscopy (SEM). In this article, the detection of a source of naturally occurring perchlorate in soil and groundwater associated with the Mission Valley Formation in San Diego California is presented. Modification of existing agricultural soil sampling techniques USDA 60-6(...

†Dr. Robert D. Morrison is a Soil Physicist with DPRA, Inc. He has a BS in Geology, a MS in Environmental Studies, a MS in Environmental Engineering and a Ph.D. in Soil Physics from the University of Wisconsin at Madison. Dr. Morrison has been working for 30 years in the environmental field on issues related to soil and groundwater contamination. Dr. Morrison specializes in the forensic review and interpretation of scientific data for the purpose of identifying the source and age of a contaminant release. Emily A.Vavricka is an Environmental Scientist with DPRA, Inc. She possesses a BS in Environmental Science from the University of California, Riverside, and specializes in the use of environmental forensics for use in litigation matters.

1,4-dioxane (dioxane) is an emerging contaminant of concern and is quickly gaining dominance as a key contaminant in groundwater. Domestic and municipal water-supply wells have been impacted by 1,4...

(2002). The Forensic Detection of Explosives in the Subsurface. Environmental Claims Journal: Vol. 14, No. 3, pp. 351-367.

(2002). Contaminant Source Identification with Soil Gas Surveys. Environmental Claims Journal: Vol. 14, No. 1, pp. 99-111.

A multitude of forensic techniques are available for age dating and source identification, including aerial photography interpretation, corrosion models, the commercial availability of a compound, chemical associations with discrete type processes, chemical profiling, degradation models and contaminant transport models. These techniques, however, are rarely challenged or discussed in the literature relative to the scrutiny encountered in environmental litigation. When introduced as scientific evidence, the governing assumptions and quality of the data are critically evaluated and frequently successfully challenged. The purpose of this paper is to review five types of forensic techniques and discuss their merits so that a user can decide which technique, or combination of techniques, is most appropriate for developing the technical portion of a case.

Historical aerial photography can be a powerful tool in environmental forensic investigations. Historical aerial photography is available for many sites from the 1930s on. It is researched and obtained from both public and private sources. Most of the photography consists of vertical stereoscopic film annotated with the date of the photomission. A current photomission can be flown using airborne GPS for precise registration of the photomosaics. The photography is scanned at a very high resolution and registered in a coordinate system using a digital stereoplotter that removes terrain distortion and allows the precise measurement of objects. The digital stereoplotter is used to produce photomosaics and to interpret environmentally significant features in the photography. The accuracy of the environmental interpretations is dependent on the skill and experience of the interpreter as well as the resolution of the photography and quality of the equipment used. The photomosaics are then registered in a geographic information system along with the interpretations of environmentally significant features. In a similar manner, historic maps are scanned and registered into the same coordinate system. The interpreted images and maps form a significant part of the expert report. A computer projection system is used to show the interpreted images at trial.

A multitude of forensic techniques are available for age dating and source identification, including corrosion models for underground storage tanks, the commercial availability of a compound, chemical associations with discrete types of manufacturing processes, chemical profiling, proprietary additives, stable isotope analysis, degradation models, biomarkers and contaminant transport models. The selection and use of these techniques in environmental litigation must be thoroughly understood and applied to be effective as forensic evidence. When introduced as scientific evidence, the governing assumptions and quality of the data are critically evaluated and frequently successfully challenged. The purpose of this paper is to present an overview of commonly used environmental forensic techniques and their possible applications so that a user can decide which technique or combination of methods is most appropriate for their case.

The transport time required for a contaminant to move through the subsurface is frequently encountered in insurance coverage cases. Transport calculations are often offered as evidence that (1) a contaminant was released within a particular policy period or (2) a contaminant entered the soil and/or groundwater during a specific policy period. The various transport processes and the assumptions used in these calculations are presented along with examples in this article.