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OIP-G Successfully Detects Coal Tar Fluorescence Adapted from Information by Geoprobe Systems ® The Optical Imaging Profiler (OIP) is a direct push photo-logging system devel- oped by Geoprobe ® . It uses a downhole light source and complementary metal- oxide semiconductor (CMOS) camera to investigate for fluorescent contaminants through a sapphire window on the side of the probe. Intended for use in soils and unconsolidated formations, the OIP probe was initially developed with an ultraviolet (UV) light emitting diode for the detection of fuel fluorescence. Several common organic contaminants of concern (coal tars, creosote, bunker fuels) yield inconsistent results under UV l ight, but do fluoresce under green wavelength light. So Geoprobe ® developed an OIP probe with a green wavelength light source - the OIP-G - in which the downhole camera acquires images of fluores- cence at 30 frames per second, displaying them on-screen during logging. The images are analyzed for the percent area of fluorescence (%AF), and one image every 0.05 feet is saved to the log file. If there is no fluorescence, the images are dark. The OIP-G probe includes a dipole e lectrical conductivity (EC) array for the measurement of bulk formation EC . The EC and %AF logs are dis- played onscreen along with the images o f fluorescence as the probe is advanced. Geoprobe ® coordinated with Gary Rich ards and Jonathan Stephenson of the Kansas Department of Health and Environment (KDHE) and their contractor GSI Engineering of Wichita, K ansas, to conduct a test of the OIP-G system at the former manufactured gas plant in Wellington, Kansas. The site is underlain by clay-rich alluv ium with silty to sandy interbeds to a depth of about 30 feet with Permian A ge shale as the bedrock. OIP-G logs were completed at 39 locations to de pths of up to 33 feet. Logs from the Wellington site revealed the presence o f significant fluorescence at sev- eral locations and depths. Sampling was p erformed at selected locations and targeted depths based on the fluoresce nce logs. The samples collected with the Geoprobe ® DT22 soil coring syste m were submitted for analysis of polycyclic aromatic hydrocarbons (PAH), which are also known as polynuclear aromatic hydrocarbons. Lab analyses revealed the presence of elevated PAH concentrations in most samples. Importantly, sampling revealed false positive results (up to 40%AF) were detected at a few locations. Bench tests with dilute hydrochloric acid revealed the false positive results occurred due to the presence of calcareous minerals. The flu- orescence of calcite is well-documented. Inspection of the targeted core samples quickly verified the presence of coal tars, calcareous sediments, caliche nodules. Following fieldwork, cross sections with EC and %AF logs helped to define the presence and distribution of coal tars in the subsurface and identify preferential migration pathways. These results indi- cate the OIP-G system is a useful tool for investigation of facilities with coal tar con- tamination. Members of GSI Engineering and the Kansas Department of Health & Environment running an OIP-G log in front of the former manufactured gas plant building, which has been converted to a railroad museum. ENV 38 MAY 2019 WorldWide Drilling Resource ®