U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

Detection and Site Characterization

Multi-Component Waste

Induced Fluorescence

In Situ Characterization of NAPL with TarGOST® Laser Induced Fluorescence

The TarGOST®, a modified version of the Rapid Optical Screening Tool (ROST®), uses visible wavelength fluorescence spectroscopy to yield a monotonic response in the presence of coal tar in soil. The TarGOST® is capable of logging 300 to 500 ft/day at 10 to 20 separate probing locations.

Case Study: Confirmation of TarGOST Laser-Induced Fluorescence DNAPL Delineation with Soil Boring Data
M.B. Okin, S.M. Carroll, W.R. Fisher, and R.W. St. Germain.
Land Contamination & Reclamation, Vol 14 No 2, p 502-507, 2006

The TarGOST® was used at a manufactured gas plant (MGP) site to provide a real-time, semi-quantitative assessment of the extent of coal tar contamination in an investigation that took place on land using a cone penetrometer test (CPT) rig and on water using a barge with a Geoprobe® to assess sediment contamination. Confirmation sampling agreed with the TarGOST® results. The investigation showed a strong correlation between the presence of coal tar as detected by TarGOST® and the presence of sandy layers in the subsurface. The investigation also indicated the presence of coal tars at some distance from source areas in thin, highly permeable seams found in lower permeability units. Without the use of the direct push equipment and the TarGOST® probe, these seams most likely would have been missed.

Development of a Characterization and Assessment Framework for Coal Tar at MGP Sites: Coal Tar Management Frameworks.
EPRI, Palo Alto, CA: 104 pp, 2006

This report describes a characterization assessment framework for MGP DNAPLs. The report confirms the ability of laser fluorescence technology (TarGOST®) to vertically and horizontally delineate the extent of subsurface DNAPLs.

Gowanus Canal Superfund Site. IV: Delineation of Potentially Migrating NAPL Layers for ISS Treatment
Gee, G.L., D.G. Grubb, J.L. Gentry, C.D. Tsiamis, and J. Hess.
Journal of Hazardous, Toxic, and Radioactive Waste 26(3)(2022)

This paper presents the decision-making strategy applied to select areas to implement ISS to a depth of 5 ft into the native sediments at the Gowanus Canal Superfund site after dredging the overlying soft sediments in remedial target areas (RTAs)-1 and -2. Historic operation of three manufactured gas plants resulted in NAPL impacts. ISS target areas were developed primarily from in-canal Tar-specific Green Optical Screening Tool (TarGOST) analysis of sediments at a 2-in. (5 cm) layer resolution and an empirical correlation relating the TarGOST percent reference emitter response to the NAPL pore fluid saturation (PFS) in the cores, and the measured NAPL PFS threshold above which NAPL was potentially mobile. A volume accommodation model (VAM) evaluated the ability of various individual NAPL PFS exceedances and their associated layer thicknesses in the sediment to trigger a PFS exceedance above the threshold value of the entire overlying horizon, resulting in NAPL breakthrough from as deep as 10 ft into the native sediment. The output from the VAM was integrated with ArcGIS spatial mapping and visualization tools to generate Thiessen polygons that indicated the areas having overall NAPL exceedances. Mobile NAPL areas were identified and effectively targeted for ISS, totaling 82,798 and 227,297 ft2 (7,692 and 21,117 m2) in RTA-1 and -2, respectively, or 15,227 and 49,843 yd3 (11,642 and 38,128 m3) based on the ISS mass thickness. View abstract

In Situ Characterization of NAPL with TarGOST at MGP Sites
R. St. Germain, S. Adamek, and T. Rudolph.
Land Contamination & Reclamation, Volume 14, Number 2, 2006, pp. 573-578(6)

Site characterization of former MGP sites where coal tars and associated chemicals are found can be challenging. The tendency for coal tar to sink into the subsurface following the path of least resistance can require a large number of discrete sample locations to properly delineate it; however, the number of discrete samples that can be subjected to laboratory analysis is restricted by the high cost of standard methods. The TarGOST®, an alternative to conventional methods, is a direct push probe that uses a laser-induced fluorescence (LIF) instrument for contaminant detection. As it is pushed into the subsurface, this tool is specifically designed to detect coal tars.

Using TarGOST® to Delineate the Presence of Coal Tar in Subsurface Soils
Electric Power Research Institute (EPRI), Palo Alto, CA. Report No 1012131, Aug 2005

The TarGOST® LIF profiling method was applied at the Former Hackensack Gas Works site and adjacent property. EPRI and PSEG SC evaluated the results and effectiveness of the tool to locate coal tar in the subsurface due to the availability of recently collected site characterization information and the need to characterize the presence of coal tar that appeared to have migrated from the site onto an adjacent property. This evaluation was accomplished by advancing the TarGOST® technology at as many boring locations as possible within a 5-day field period to build a robust data set. Selected TarGOST® probe locations were drilled both to compare soil conditions visually and to evaluate soils using the LIF technology. Information gathered during this technology evaluation program was to be used in the evaluation of remedial action objectives for the site. The investigators first used TarGOST® to characterize general subsurface conditions at the site and then to delineate the extent of coal tar formerly observed in specific areas of the site and to determine if coal tar exists beyond those points. Conventional DPT was used to collect soil cores for comparison with and evaluation of the effectiveness of TarGOST®. When the data were evaluated, the technology was found to be an effective coal tar characterization and delineation tool. TarGOST® is useful to site managers in the following applications: characterizing and delineating the extent of coal tar; limited differentiation between separate, unique sources of coal tar within a study area; better geologic characterization when coupled with conventional soil borings; and rapid screening of large areas before collecting confirmatory delineation samples.

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