Background/Objectives: Understanding the distribution of petroleum non-aqueous phase liquid (NAPL) has been a focus of high-resolution site characterization (HRSC) since the early 1990s, with the development of the laser induced florescence (LIF) Rapid Optical Screening Tool (ROST™) by Dakota Technologies, Inc. (Dakota) which was later developed into the Ultra Violet Optical Screening Tool (UVOST®) circa 1997.
Both ROST™ and UVOST® targeted light NAPL (LNAPL) such as gasoline and diesel fuel using ultraviolet light. In 2003, Dakota developed the TarGOST® tool for petroleum dense NAPL (DNAPL) sites using visible light. Typically, the UVOST® or TarGOST® tools are implemented with a cone penetrometer testing (CPT) tool to understand the geotechnical conditions and lithostratigraphy at NAPL impacted sites. For sites that have a comingled petroleum DNAPL and LNAPL conditions, a combined tool was necessary to minimize the time and costs for multiple pushes for each tool separately.
Approach/Activities: In late 2014, Geosyntec Consultants and Dakota developed a tool that combines UVOST®, TarGOST®, and CPT into one direct push; thus, effectively reducing the field scope in half; and providing critical information necessary for comingled petroleum LNAPL and DNAPL sites. The combined CPT and LIF (CPT/LIF) tool has been implemented during two field mobilizations and has been evaluated using correlative conventional coring to convert the qualitative field screening of the combined tooling into quantitative values of NAPL pore saturation for both petroleum DNAPL and LNAPL. Additionally, the responses from the combined CPT/LIF tool were interpreted using clustering diagram analysis and correlated to laboratory chromatograms to provide further use of the tool to understand the types of petroleum DNAPL and LNAPL released.
Results/Lessons Learned: The use of the combined CPT/LIF tool is most beneficial for sites with known comingled NAPL bodies of lighter and denser petroleum hydrocarbons. This tool aids in understanding the dynamics of a complex NAPL architecture. Here we illustrate the usefulness of this combined tool to further the development of HRSC tools, and provide examples of the output and capabilities of the new HRSC tool.