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13336 East Highway 88 - 3 - 1 October 1998 <br /> Lockeford, San Joaquin County <br /> and an odor was noted on the boring log at 30 feet bgs. Soil ' <br /> samples collected from boring B7, between <br /> 20 and 60 feet bgs contained elevated concentrations of TPHg (to 45 feet bgs), and,BTEX constituents. <br /> (to 60 feet bgs). Below 70 feet bgs, soil samples were analyzed fo'r'TCLP only. <br /> The elevated concentrations of TPHg, and BTEX constituents in the groundwater sample warrant -an <br /> investigation to determine the lateral and vertical extent of groundwater contamination. The groundwater <br /> investigation must include drilling three soil borings to groundwater, and collecting discrete soil samples <br /> from the capillary fringe, and saturated zone in each borehole. Groundwater samples must be collected <br /> from each borehole using a technology that will provide samples representative of chemical, and . <br /> hydrogeologic conditions. This may be completed using the SimulProbe®, or comparable technology. <br /> The alternative to using an effective sampling technology to provide representative groundwater samples <br />.-- .—is,to.,.convert_each_boreehole..to-a groundwater:mon taring:well., and_:begin a.groundwater <br /> monitoring program. Soil and groundwater samples must be analyzed for TPHg, BTEX and the <br /> oxygenates. No TCLP analysis will be required for these samples': The oxygenate analysis is necessary <br /> because tertiary-Butyl Alcohol (TBA) was detected at 96 gg/.Kin'the soil sample collected from boring <br /> B7 at 49 to 50 feet bgs. <br /> Based on residual contaminant mass calculations provided by GeoSoly, approximately 67,812-kilograms <br /> (4,400-gallons) of TPHg and 895-kilograms (58 gallons) of benzene are estimated to remain in the soil at <br /> the site. If the requested groundwater samples are non-detect for,all contaminants, a fate and transport <br /> IL <br /> model must be run to demonstrate that the residual contaminant mass will not'adversely impact <br /> groundwater quality. If, however, the groundwater.samples,are impacted by petroleum hydrocarbons, <br /> additional work may be required. <br /> Summary: <br /> The single groundwater grab sample collected from soil boring B7 on 1 July`1998 contained elevated <br /> concentrations of TPHg, benzene and toluene. Mr. Goldmani of GeoSoly attributed the elevated <br /> concentrations of petroleum constituents to cross-contamination of,the bailer during its descent down the <br /> center of the augers, to leaching of contaminants to groundwater,'through another migratory pathway, or <br /># to vapor phase migration. None of.these hypotheses can be conf rmed or denied_using the.available data. <br /> Based:on elevated concentrations of TPHg; benzene and „toluene in the groundwater sample, I am <br /> requesting that three soil borings be drilled to groundwater;' Soil $samples are to be collected from the <br /> capillary fringe and saturated zone, and groundwater samples are:to be collected from each boring using <br /> a technology that will provide samples representative of chemical and hydrogeologic conditions at the <br /> site. Until groundwater conditions are assessed at the site, site closure cannot be considered. <br />