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 Presented by William M. Davis (
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Triad Environmental Solutions, Inc.
Decatur, GA, USA
Dense non-aqueous phase liquid (DNAPL) contaminated sites are among the most difficult sites to characterize and remediate. This is due do a number of factors, including the unique nature of DNAPL transport and the heterogeneous subsurface geology encountered at most sites. Many DNAPL sites have been under investigation for multiple decades with little success in locating the actual source areas. Advances in site characterization tools over the last 10 years have made it possible to cost effectively collect the high density data sets necessary to accurately assess DNAPL source zones.
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 Presented by Randy St. Germain (
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Dakota Technologies Inc.
Fargo, North Dakota, USA
Multi-component dense non-aqueous phase liquid (DNAPL) such as coal tar and creosote are potent source terms for polycyclic aromatic hydrocarbons (PAHs) due to PAH’s affinity for NAPL vs water. But creosote, coal tar, and bunker fuel remain “fringe” contaminants of interest in the sense that while investigators recognize their risk, they often underestimate the difficulty involved in properly characterizing these complex materials. Because they are “black goos” it is often assumed you can delineate them accurately with basic sampling and field observations and/or the usual laundry list of chemical analyses that speciate components. But multi-component DNAPLs are highly variable and heterogeneously distributed contaminants that are very difficult to delineate accurately. We’ll describe two innovative optical methods capable of rapidly and cost-effectively screening soils and sediments for these PAH-containing DNAPLs.
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 Presented by Seth Pitkin (
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Stone Environmental, Inc.
Montpelier, Vermont, USA
The characteristics of DNAPLs coupled with the scale of heterogeneity in subsurface hydrogeologic systems results in very complex distributions of DNAPL in geologic media, both porous and fractured. A brief review of the physics controlling DNAPL movement in porous media will be presented followed by a discussion of approaches to the investigation of sites contaminated with DNAPL. While it is critical that the investigator pay attention to the presence, location and distribution of the DNAPL, this is only one aspect of a complicated system involving multiple phases in a spatially variable framework. The components of an adequate site investigation include:
- the development of a detailed conceptual site model
- High resolution site investigation methods
- Small sample interval
- Close sample spacing
- Use of the transect approach
- Use of collaborative data platforms
- Rapid low cost screening methods coupled with
- Definitive higher cost methods
- Use of integrated data sets (i.e., combinations of types of data)
- Hydrostratigraphic
- Contaminant
- Dynamic work strategies with real-time data
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 Presented by Joe Rossabi (
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Redox Tech, LLC
Cary, North Carolina, USA
Dense Non-Aqueous Liquid (DNAPL) contamination at sites continues to be one of the most challenging problems in environmental characterization and remediation. The relatively small size (but large impact) and often heterogeneous distribution of NAPL confounds characterization efforts and frustrates cleanup attempts. In this workshop we offer information on tools and methods that will help improve DNAPL characterization. The DNAPL Basics section will provide the basic physics and chemistry of DNAPL in the subsurface primarily in the context of equilibrium conditions. Along with an understanding of the initial release of the contaminant, an important factor for characterizing and remediating a DNAPL site is an understanding of the ambient material properties and configuration. More often than not, geology is the key. Establishing end case perspectives on DNAPL deposition and distribution with respect to the site’s geologic materials and configuration will inform a site conceptual model and allow better choices for selecting the next step in characterization or remediation.
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